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OCR for page 36
4
Contraceptive Benefices and Risks
Pregnancy and childbirth carry risks of morbidity and mortality. Although the
contraceptives that couples use to avoid pregnancy have their own health risks,
they also have substantial noncontraceptive health benefits. Information about
these risks and benefits is necessary for informed decision making. Oral contra-
ceptives, for example, not only prevent pregnancy, but they also reduce the risk of
endometrial and ovarian cancer and protect against acute pelvic inflammatory
disease and ectopic pregnancies. However, oral contraceptives increase the risk
of cardiovascular disease. IUDs provide effective contraception but increase the
potential for infection in certain high-risk groups. Barrier methods of contract
tion provide less effective contraception, but they protect against sexually trans-
mitted infections including human immunodeficiency virus (HIV). The impor-
tance of the noncontraceptive benefits and risks of contraceptives varies among
societies because of variations in the prevalence of the diseases involved.
This chapter reviews evidence on the effectiveness and health consequences of
specific contraceptive methods. Our attention is limited to the biological conse-
quences of a method's use, even though each method may have psychological
risks and benefits. Our purpose is to provide an account of the direct health
consequences of contraceptive use, independent of the effects that fertility control
has on health by allowing women to control their fertility. This analysis is
particularly important because, in some counties, health officials downplay the
health benefits of lower fertility because they fear the adverse health effects of
widespread use of modern contraceptives, especially in circumstances in which
medical supervision of contraceptive practice is limited.
36
OCR for page 37
CONTRACEPTIVE BENEFITS AND RISKS 37
Our consideration of the effectiveness of contraceptives is based on a recent
critical review of the literature by Trussell and Kost (1987~. The studies they
examined and most of the epidemiologic and clinical studies of the health effects
of contraceptives have been carried out in developed countries. We recognize the
difficulty of generalizing these results to He special health and cultural situations
in the developing world. Furthermore, there are few studies of the effects of
various contraceptive methods on the risk of diseases that are generally limited to
developing countries. In many cases, He available data pertain to contraceptives
that were commonly used in the 1960s and early 1970s and focus on the user
population at that time. The research design, the quality of the data, the size of the
sample, and the analysis have often been insufficient to allow definitive conclu-
sions. Clearly, more studies conducted in developing countries are needed, and in
fact studies sponsored by the World Health Organization are under way. Never-
theless, we regard the available information as a reasonable guide for estimating
the risk of pregnancy versus the risks and benefits of contraceptive use in the
developing world.
ORAL CONTRACEPTIVES
According to United Nations estimates, oral contraceptives are currently used
by nearly 62 million women (IJnited Nations, 1989~. Two types of oral contra-
ceptives (OCs) are available: combination OCs, consisting of the hormones
estrogen and progestin, and the progestin~nly pill (often called the minipill).
Combination OCs are used by far more women, and as a result, most epidemiol-
ogic studies consider this type, particularly He formulations popular during the
1960s to inid-1970s. OCs prevent pregnancy primarily by inhibiting ovulation,
although changes in the cervical mucous and endometrium may also have contra-
ceptive effects. Failure rates associated with OC use are low—roughly 3 percent
of women using OCs became pregnant in the first year of use, mainly because of
improper or incomplete use (Trussell and Kost, 1987~.
Health Benefits
A large cohort study in the United Kingdom has provided clear evidence that
OC use decreases the risk of iron deficiency anemia in both current and past users
(Royal College of General Practitioners, 1970~. The effect is probably caused by
the decrease in menstrual flow and consequent increase in iron reserves. This
benefit may be especially important in developing countries in which iron defi-
ciency is a problem (Stadel, 1986~.
Case-control and cohort studies have found a decreased risk of benign breast
disease associated with OC use (Stadel, 1986~. The relative risk in women who
have used OCs for more than two years compared with nonusers is about 0.6 for
OCR for page 38
3 ~ CO=RACE"ION AND REPRODUCTION
fibrocystic disease, 0.3 for fibroadenoma, and about 0.5 for unbiopsied breast
lumps. This decreased risk does not persist in former users who have not used
OCs for more than one year (Brinton et al., 1981~. Since this effect is most likely
to be related to the high progestin content of early formulations of the pill, current
OC formulations may not decrease the risk of benign breast disease.
Several studies have found that OC use decreases the risk of functional ovarian
cysts. This effect is probably due to the suppression of ovulation (Stadel, 1986~.
Evidence also suggests that OCs protect against uterine fibroids, the protection
increasing with the duration of OC use (Ross et al., 1986~. While there is still
speculation about the mechanism, the protective effect against fibroids may be
related to how the effect of circulating estrogens, which may promote the forma-
tion of fibroids, is modified by the progestins in OCs.
Several studies in developed and developing countries have found that current
or recent OC use reduces the risk of pelvic inflammatory disease (PID), a major
cause of female infertility (Stadel, 1986; Gray and Campbell, 1985~. These
studies have found that OC use lowers the risk by, on average, about 40 percent.
Two mechanisms may be operative: OCs may change the cervical mucous such
that it prevents pathogenic organisms from ascending into the upper genital tract;
or OCs reduce menstrual blood flow, thus decreasing the amount of medium
available for bacterial growth (Rubin et al., 1982~. Unfortunately, most of the
studies of oral contraceptives and PID have been hospital-based, so the results
may not apply to women who are asymptomatic or who have PID not requiring
hospitalization (Washington et al., 1985~. For example, OCs may protect against
gonorrhea, an important cause of acute PID that would require hospitalization,
whereas other bacterial etiologies that cause less severe PID, such as chlamydia,
may receive little or no protection from OC use.
Because they are highly effective at inhibiting ovulation, OCs greatly decrease
the risk of ectopic pregnancy. Results from large case-control studies conducted
in the United States and developing countries found that current OC users were 10
times less likely to have an ectopic pregnancy than women using no method (Ory
and the Women's Health Study, 1981; Gray, 19841. Because the risk of death
from ectopic pregnancy is high for women living in rural areas in the developing
world, this effect is particularly noteworthy.
Another important benefit from OC use is a reduction in the risk of endometrial
and ovarian cancer. Several epidemiologic studies have confused reduction of
endometnal cancer among users. The Cancer and Steroid Hormone (CASH)
study conducted in the United States found a 40 percent reduction in the risk of
endometrial cancer, even long after OC use had been discontinued, and the benefit
increased with the cumulative duration of pill use (Centers for Disease Control
and the National Institute of Child Health and Human Development, 1987a,
1987b). The continued protection the pill provides to former users is not clearly
understood, but apparently the carcinogenic effect of estrogen on the endomet-
rium is obviated by the progestin in the pill.
OCR for page 39
CONTRA CEPTiVE BENEFITS AND RISKS 39
The CASH study also found a 40 percent reduction In the risk of ovarian
cancer (Centers for Disease Control and National Institute of Child Health and
Human Development, 1987a, 1987b). Other epidemiologic studies have sup-
ported these findings. Suppression of ovulation and suppression of secretion of
the hormone gonadotropin have both been postulated as mechanisms of this
protection. It is noteworthy that there is consistent evidence from independent
epidemiologic studies that the pill protects women from endometrial and ovarian
cancer. Such consistency suggests true biological effect.
Adverse Heals Effects: Cardiovascular Diseases
Cardiovascular diseases are a major cause of death in developed countries,
where most research on the association between OC use and cardiovascular
diseases has been conducted. These diseases are less common in developing
countries, so alteration in their occurrence by OC use may not be as substantial as
in industrialized countries.
OC use increases the risk of cardiovascular disease, in particular the risk of
venous thromboembolism, myocardial infarction, and stroke (Stadel, 1986; Pren-
tice and Thomas, 1987; Vessey, 1980~. The risk of serious illness or death
attributable to OC use from adverse cardiovascular effects is concentrated primar-
ily among older women over age 30 and women who smoke cigarettes or have
other cardiovascular risk factors. The excess risk of cardiovascular diseases
seems to be directly related to both the estrogen and progestin content of the pill.
And the risks may be substantially lower with newer low-dose preparations.
Venous thrombosis is the blockage of a vein by a blood clot particle. Throm-
boembolism occurs when the blood clot moves from a primary site to another,
such as to the lungs or the brain. It is a major source of illness that may lead to
death. Although the risk of venous thromboembolism is increased for current OC
users, the increased risk does not persist among former users and is not related to
duration of use (Vessey, 1980~. The higher the estrogen content of the OC, the
greater is the risk of venous thromboembolism, both for superficial and deep vein
thrombosis (Stadel, 1986~. The risk of venous thromboembolism among pill
users appears to be unrelated to cigarette smoking. Mechanisms underlying
increases in venous thromboembolism involve effects of estrogen or blood clot-
ting factors that increase the coagulability of blood.
Myocardial infarction and stroke are much more important causes of mortality
attributable to OCs. The risk is strongly influenced by age and by the presence of
over cardiovascular risk factors, including cigarette smoking, hypertension, and
diabetes. The annual risk of myocardial infarction attributable to current OC use
rises from about 4 cases per 100,000 among nonsmoking OC users ages 30 to 39
to 185 cases per 100,000 among heavy-smoking OC users ages 40 to 44 (Stadel,
1986~. Current OC use has been found to slightly elevate blood pressure in most
women, possibly a contributing factor to the pathogenesis of myocardial infarc-
OCR for page 40
40 CONTRACEPTION ID PRODUCTION
lion and stroke among current OC users. OC use leads to a three- to sixfold
increase in the risk of overt hypertension, increasing with a woman's age and
duration of OC use. It must be remembered that these risks pertain to use of the
relatively high-dose pills of the 1960s and 1970s and their patterns of use in
relation to such factors as age and smoking.
Other Possible Health Effects
Metabolic Effects
Metabolic changes may underlie the effects of OCs on myocardial infarction.
Estrogens have the apparently desirable effect of increasing HDL-cholesterol
(high density lipoprotein) concentration. Depending on type, progestins may
either increase, decrease, or have no effect on HDL-cholesterol (for a complete
discussion of changes in HDL-cholesterol, see Vessey, 1980~. The net effect of
different OC formulations on HDL-cholesterol is a function of both the dose of
estrogen and the dose and type of progestin (Stadel, 1986~.
Current OC use has been found to decrease glucose tolerance in most women,
although this decrease appears to be small and unrelated to duration of use. This
decrease is directly related to the estrogen content of the OCs (Stadel, 19863.
-
Neoplasac Diseases
Me forms of neoplasia that are of greatest concern with the potential effects of
OC use are breast cancer, cervical cancer, endometrial cancer, and ovarian cancer.
There are two main reasons for the concem. First, these cancers are major causes
of morbidity and mortality, particularly breast cancer in developed countries and
cervical cancer in some developing countries.) Second, the breast, the uterus, and
the ovaries are endocrine-dependent organs, and a large body of research shows
that hormonally related factors, such as age at menarche and age at first birth,
affect the risk of developing neoplastic diseases. Thus, any factor that alters
hormones requires careful scrutiny as a possible carcinogen or anticarcinogen for
these organs. In addition, cervical cancer is caused by the human papiloma virus,
and contraception may modify transmission.
Complex methodological problems make the study of possible relationships
between OC use and these cancers difficult. Such problems include a possible
long latency period and the difficulty of evaluating factors that might alter the
effects of OCs, such as age at first pregnancy for breast cancer and the number of
sexual partners for cervical cancer. In fact, some studies on breast and cervical
cancer among OC users have found no effect on cancer risk and others have
Approximately 6 percent of British women and 9 percent of American women develop cancer of
the breast during their lives (Schlesselman et al., 1988).
OCR for page 41
CONTRACEPTIVE BENEFITS AND RISKS 4~
OCR for page 42
42 CONTRA CESSION ID REPRODUCTION
the major epidemiologic studies conducted have found no increased risk and
some have found significantly increased risk, at least in certain subgroups (Piper,
1985; Brinton et al., 1986; Ebeling et al., 1987; Irwin et al., 1988~. A large study
by the World Health Organization, which included many developing countries,
found some indication of increased risk with prolonged OC use (World Health
Organization, 1985a), but these studies have serious methodological problems,
most notably a detection bias caused by increased Pap screening of OC users
compared with nonusers and differences in sexual behavior among users and
nonusers of OCs (Piper, 1985; Swan andPetitti,1982~. More recent studies have
attempted to address these methodological problems, but the results remain con-
flicting. While OCs probably do not dramatically increase the overall risk of
cervical dysplasia or cancer, long-term OC use or use by specific subgroups of
women may increase the risk. Two large British cohort studies have shown a
higher incidence of cervical neoplasia among oral contraceptive users (Vessey et
al., 1983; Beral et al., 1988~. The most important conclusion from the conflict
over these results is the importance of annual Pap screening in the prevention of
invasive cervical cancer.
OCs have been associated with malignant melanoma (skin cancer), but the
association is rather weak and possibly confounded by differences in exposure to
sunlight (Stadel, 1986~. Some studies do suggest an increase within certain
subgroups of women, particularly those with long-term use (Bain et al., 1982;
Beral et al., 1984; Holly et al., 1983; Ramcharan et al., 1981~. Due to the rarity of
this malignancy in developing countries, however, the attributable risk is quite
low and not very important for public health policy.
Recent case-control studies have found an increased risk of hepatocellular
carcinoma (liver cancer) among OC users, largely confined to long-term users
(Forman et al., 1986; Neuberger et al., 1986;~Henderson et al., 1983~. Unfortu-
nately, these studies all had small sample sizes and methodological problems that
may have biased the results. Since hepatocellular carcinoma is extremely rare in
developed countries, the attributable risk is very low. The disease is a much more
common problem in many developing countries, especially where there is a high
prevalence of chronic hepatitis B. The interrelationships among OC use, hepatitis
B. and liver cancer are not well understood. The World Health Organization is
conducting a multicenter case-control study in three developing countries to
address the question.
It is clear that OC use increases the risk of hepatocellular adenoma (HCA), a
rare, benign tumor of the liver that can cause serious intra-abdominal hemorrhage
and death. The case fatality rate is approximately ~ percent (Rooks et al., 1979~.
The risk attributable to OC use is very low, estimated to be about 2 cases of HCA
per 100,000 users per year among women who have used OCs five years or more
(Stadel, 1986~.
OCR for page 43
CONTRACEPTIVE BENEFITS AND RISKS 43
Other Effects
It has been suggested that OC use might accelerate the appearance of gall
bladder disease in susceptible women (Royal College of General Practitioners,
1982), although evidence for this hypothesis is limited. Early studies (Boston
Collaborative Drug Surveillance Program, 1974; Royal College of General Prac-
titioners, 1982) suggested that the risk of gall bladder disease might be increased
in OC users. Recent studies and further analysis of information from British
studies, which had first shown an increased risk of gallbladder disease in OC users
(Layde et al., 1982; Wingrave and Kay, 1982), have failed to confab this
association.
There have been extensive studies of the effects on pregnancy outcome of
hormonal contraceptive use prior to or during pregnancy. Although there are
some reports of adverse effects, the majority of studies show no increased risks,
and several comprehensive reviews of the literature have concluded that in utero
exposure to synthetic steroids at the doses used for contraception does not result
in significant deleterious effects on fetal growth or development (Wilson and
Brent, 1981; World Health Organization, 1981; Simpson, 1985~.
Even at low doses, the estrogen component of combination OCs has been
shown to suppress milk volume in lactating mothers. Progestin-only contracep-
tives, including the minipill and tong-acting methods discussed below, do not
suppress milk production and can be used by breastfeeding women (World Health
Organization, 1981~. Although the synthetic hormones of the pill do pass on to
the suckling infant, no adverse effects have been observed. Some reports have
postulated an association between birth defects and the use of hormonal contra-
ceptives prior to or during pregnancy. However, the majority of studies show no
increased risks of deleterious effects on fetal growth or development (Wilson and
Brent, 1981; World Health Organization, 1981; Simpson, 19851.
INTRAUTERINE DEVICES
The intrauterine device (IUD), which is inserted and remains in the uterus,
prevents conception through several modes of action. IUDs may be medicated or
nonmedicated; examples include the inert Lippes Loop, Copper-T (medicated
with~copper), and Progestasert (medicated with progesterone). The IUD is highly
effective, having a failure rate of less than 6 percent in the first year of use. Many
failures are due to undetected IUD expulsion (Trussell and Kost, 1987~. It
appears thee new copper IUDs have a much lower failure rate of 1 to 2 percent.
Rates of IUD use vary widely among countries. Partly because of its widespread
use in China, the IUD is the most commonly used, reversible method of birth
control in the world. IUDs are currently used by roughly 79 million women,
nearly 58 million of whom live in China (United Nations, 1989~.
OCR for page 44
44 CONTRACEPTION ED REPRODUCTION
Because IUDs appear to prevent both intrauterine and ectopic pregnancies, the
overall risk of ectopic pregnancy is decreased by IUD use by about 60 percent,
according to U.S. and multinational WHO studies (Ory and the Women's Health
Study, 1981; Gray, 1984~. However, 5 to 15 percent of IUD-associated pregnan-
cies are ectopic, indicating that the IUD is more effective at preventing intrauter-
ine pregnancies. Progesterone-releasing IUDs decrease menstrual blood loss and
dysmenorrhea (Hatcher et al., 1988~. No other noncontraceptive health benefits
to IUD use have been identified. ~~
Major health risks that have been associated with IUD use include pelvic
inflammatory disease, tubal infertility, septic abortion, spontaneous abortion, and
uterine perforation. The attributable mortality risk is extremely low in the United
States, estimated at 1 to 2 deaths per 100,000 users and was mainly due to the now
discontinued Dalkon Shield (Ory et al., 1983~. Where access to medical facilities
is poor and diagnosis and treatment of complications are delayed, mortality rates
may be higher.
Unlike other modern methods of temporary contraception, the IUD increases
the risk of pelvic inflammatory disease (Grimes, 1987~. PID is usually, although
not always, the result of sexually transmitted diseases (STDs). As a result, much
of the risk of PID attributed to IUD use is mainly in women who are at increased
risk for developing STDs. In the United States, women using IUD types other
than the Dalkon Shield have been found to have about 1.5 to 2.0 times greater risk
of PID than women using no method. Corresponding data in developing coun-
tries shows a relative risk of 2.3 (Gray and Campbell, 1984~. The risk is largely
concentrated in the first few months after IUD insertion, because insertion may
introduce bacteria into the uterus Wee et al., 1988~.
The presence of PID has been clearly linked to subsequent tubal infertility.
Two U.S. case-control studies found that the risk of tubal infertility among
nulliparous women who ever used an IUD was double that of nonusers (Daring et
al., 1985; Cramer et al., 1985~. Apparently, this increased risk of tubal infertility
is related to the presence of PID, even if PID is never recognized clinically.
However, women who reported having only one sexual partner had no increased
risk of tubal infertility associated with IUD use (Cramer et al., 1985~. Therefore,
in populations in which STDs are a major problem, it may be less advisable to
promote IUD use. In countries such as China, however, where STDs are uncom-
mon, the IUD is a safe and acceptable method.
If a pregnancy does occur with an IUD in place, a spontaneous abortion is
likely, occurring in 50 percent of cases in which the IUD is left in place and 25
percent of cases in which it is removed (Hatcher et al., 1988~. When the IUD is
left in place, septic abortion in the second trimester may result and can possibly be
fatal to the IUD user.
Perforation of the uterus may occur during IUD insertion but this is relatively
rare, probably occurring in less than 1 percent of insertions, and usually is not
serious (Hatcher et al., 1988~. The risk of perforation is substantially increased
OCR for page 45
CONTRA CEPT~E BENEFITS AND RISKS 45
among breastfeeding women and women between weeks 1 and ~ after delivery
(but less during the first 4 or 5 days pos~m3, evidently due to softer uterine
musculature (Heartwell and Schlesselman, 1983~. In general, it is recommended
that the IUD be removed when perforation occurs.
BARRIER METHODS
Because they may prevent transmission of sexually transmitted diseases, in-
cluding the human immunodeficiency virus (HIV), a great deal of attention is
being focused on spermicides and barrier methods of contraception, principally
condoms, diaphragms, and sponges. The United Nations estimates that 48 million
women or their partners use these methods, but this number may be growing
rapidly (United Nations, 1989~. The effectiveness of these methods is highly
dependent on user motivation and compliance. As a result' average failure rates
tend to be higher than for any other modern method of contraception.
Condoms are a very safe method of birth control, but their effectiveness as a
contraceptive and as a disease prophylactic depends on consistent and proper use.
Failure rates are estimated to be as high as 12 percent per year in practice (Trussell
and Kost, 1987~. A number of in vitro studies have demonstrated that latex
condoms are effective barriers to herpes simplex virus type 2, chlamydia tracho-
matis, cytomegalovirus, and HIV. Condoms evidently reduce the transmission of
organisms present in the semen, such as Neisseria gonorrhoeae, hepatitis B virus,
and Trichomonas vaginalis (Conant et al., 1984; Judson et al., in press; Katznel-
son et al., 1984; Conant et al., 1986; Stone et al., 1986~.
Data regarding in viva condom use and STDs is limited. Several studies have
found a lower frequency of gonorrhea and HIV infection among condom users
and/or their partners (Barlow, 1977; Hart, 1974; Hooper et al., 1978; Fischl et al.,
1987; Centers for Disease Control, 1987~. However, these studies are confounded
by the fact that condom users are likely to differ from nonusers in many important
characteristics (Feldblum and Fortney, 1988~. Still, while the evidence is incon-
clusive, available data suggest that condoms may be quite effective STD prophy-
lactics (Horsburgh et al., 1987~. Their failure to protect is explained more
probably by misuse than by product failure (Centers for Disease Control, 1988~.
Spermicides are chemical agents that inactivate sperm in the vagina before
they can move into the upper genital tract. The contraceptive sponge with
spermicides may provide some protection against STDs, although, as with other
barrier methods, the effectiveness of this contraceptive is highly dependent on
user compliance. Failure rates in the first year of use may be as high as 18 percent
among nulliparous women and close to 30 percent among parous women (Trussell
and Kost, 1987~. Laboratory and clinical evidence suggests that their virucidal
effects may inhibit the growth of Neiserria gonorrhoeae (Cowan and Cree, 1973;
Singh et al., 1972), herpes simplex virus type 2 (Singh et al., 1976), and HIV
(Hicks et al., 1985~. Although evidence is sparse, there is some indication that
OCR for page 46
46 CONTRACEPTION ED REPRODUCTION
spermicides also protect against cervical cancer, which has been associated with
the human papilloma vines (Spring and Gruber, 1985~.
The sponge also has attendant health risks. Sponge users may be at increased
risk of vaginal candidiasis, because normal bacterial growth is suppressed by
certain types of spermicide, which leads to the overgrowth of candida (Rosenberg
et al., 1987~. There is also an association between the sponge and toxic shock
syndrome (TSS), which in severe cases can lead to shock, coma, or death. Sponge
users are apparently at 10.5 times greater risk of TSS than women using no barrier
method (Schwartz et al., 1989~.- However, the attributable risk is low, since TSS
is an extremely rare disease.
The diaphragm (with spermicide), like the condom, if used correctly and
consistently, can be an effective contraceptive. Because of inadequate motiva-
tion, improper fitting, or inconsistent use, the average failure rate is roughly 18
percent per year (Trussell and Kost, 1987~. The diaphragm appears to reduce the
risk of gonorrhea, PID, and tubal infertility (Jick et al., 1982; Kelaghan et al.,
1982; Cramer et al., 1987~. Several studies have shown cervical dysplasia and
cervical neoplasia to be less common among users (Wright et al., 1978; Harris et
al., 1980; Celentano et al., 1987~. Since diaphragms and sponges are almost
always used with spermicides, it is difficult to separate the specific effects of
each.
As with the sponge, the risk of TSS is significantly increased for diaphragm
users (Schwartz et al., 1989~. Still, the attributable risk is only about 0.2 percent
annually. A less serious, but more frequent, complication associated with dia-
phragm use is urinary tract infections, occurring 2 to 3 times more often among
users than nonusers Oman and Frerichs, 1985; Fihn et al., 1985; Vessey et al.,
1987~.
LONG-ACTING CONTRACEPTIVES
Several long-acting contraceptive methods have been developed, consisting
mainly of injectables and implants. Usage is still relatively low, with just over 6
million women estimated to be using injectables United Nations, 1989~. These
methods are highly effective and convenient to use and give protection from
pregnancy from one month to five years. All contain a progestin, which may lead
to a disturbance of the menstrual cycle.
Injectables
Two injectable progestins, Depo-Provera (D=A) and Noristerat DEW, have
been approved in over 90 countries worldwide.2 Estimated failure rates in the fist
year of use are between 0.3 and 0.4 percent, depending on the kind of progestin
2 Neither DMPA nor NET has been approved for use in the United States. See Richard and
Lasagna (1987) for a review of the debate on approval.
OCR for page 47
CONTRACEPTIVE BENEFrTS AND R]SRS 47
used (Trussell and Kost,1987~. Injections are usually given every 8 to 12 weeks.
Injectables prevent pregnancy by inhibiting ovulation, thickening cortical mu-
cous, and altering the endometrial lining, which inhibits implantation (Liskin and
Quillin, 1982~.
.,
The relationship between the risk of cancer and the use of injectables, particu-
larly DMPA, remains controversial. The largest epidemiologic study yet pub-
lished is an ongoing case-control study conducted by the World Health Organiza-
tion. This study has found no increased risk of breast and endometrial cancer, and
an analysis of invasive cervical cancer was deemed inconclusive. Final results
concerning breast and cervical cancer are expected in the near future from this
study and from a study in New Zealand. These and other studies have been
hindered by small sample sizes and short durations of exposure. Animal data
suggest that DMPA may increase the risk of breast and endometrial cancer
(World Health Organization, 1986a).
Reported metabolic effects of the use of injectables include changes in blood
pressure and insulin, cholesterol, and triglyceride levels (Liskin et al., 1987;
WHO, 1986b). Various studies of D=A and NET users have found both
increases and decreases in total cholesterol and HDL-cholesterol. The findings
are thus inconsistent and none has shown clear clinical significance (Liskin et al.,
1987~. No studies have been published on the possible associations between
DMPA or NET use and the risk of cardiovascular disease. Unlike OCs, in-
jectables appear to have little effect on the coagulation and fibrinolytic systems
that affect blood clotting.
Amenorrhea or irregular, unpredictable bleeding episodes are the most com-
monly reported problems with injectables and the primary reason for terminating
use (World Health Organization, 1978; Swenson et al., 1980; World Health
Organization, 1987b). One-half to two-thirds of users have no regular menstrual
cycles in the first year of use (Liskin et al., 1987~. After one year of use, as many
as 50 percent of users will be amenorrheac. The occurrence of heavy bleeding is
rare, occurring in 0.5 percent of users. Conversely, since bleeding is often lighter
than normal, increased hemoglobin levels have been reported (World Health
Organization, 1986b).
Injectables appear to have no permanent effect on fertility, although ovulation
may be inhibited for four to nine months or more after the last injection (Liskin et
al., 1987; Pardthaisong et al., 1980; Affandi et al., 19873. Injectables may protect
against PID by causing changes in the cervical mucus (Gray, 19859.
Injectable progestins may protect against endometrial and ovarian cancers. A
WHO case-control study found a reduced risk of endometrial cancer in DMPA
users, but the sample was quite small and results are inconclusive (World Health
Organization, 1986a). There are even fewer data regarding ovarian cancer.
However, since injectables prevent ovulation, as do OCs, it is hypothesized that
injectables will also decrease He incidence of ovarian cancer; preliminary results
from the WHO study support this possibility.
OCR for page 48
48 CONTRACTION ED REPRODUCTION
Implants
The Norplant subdermal implant system is another highly effective progesta-
tional contraceptive. One-inch-long plastic rods are surgically implanted under
the skin of the upper arm and are left in place for several years. The progestin
levonorgestrel is slowly released and remains effective for three to five years.
The implants have a cumulative five-year net pregnancy rate of less than 2 percent
in most studies (Segal, 1988~.
Like injectables, the most common side effect of implants is disturbance of the
menstrual cycle. Episodes of abnormal bleeding diminish with duration of use
but, unlike injectables, the implants can be removed if there are extreme compli-
cations. Norplant users are generally protected from ectopic pregnancy since
ovulation is suppressed. Transient ovarian cysts occur in a small percentage of
women using Norplant, although the cysts eventually regress (Sarah et al., 1987;
Diaz et al., 1987~. Permanent infertility appears not to be a problem (Sivin et al.,
1983; Diaz et al., 1987; Affandi et al., 1987~. Several studies have shown that
fecundity quickly returns after the implants are removed. No changes have been
found in liver function, carbohydrate metabolism, blood coagulation, blood pres-
sure, or body weight Kristin et al., 1987~. Of particular importance in the use of
implants is the very low blood level of progestogen, which is much lower than
with other steroid contraceptives.
STERILIZATION
Sterilization is the most widely used contraceptive method in the world. More
than 108 million women and 41 million men have undergone sterilization proce-
dures United Nations, 1989~. Sterilization is safe and highly effective; most of
the health risks are associated with poor anesthetic or surgical technique.
Pregnancy identified after tubal sterilization may result from conception be-
fore sterilization or from unsuccessful sterilization. Failure rates, which vary by
method of tubal occlusion, surgical expertise, and patient characteristics, are
overall estimated to be between 2 and 4 per 1,000 in the first year of use (Trussell
and Kost, 1987~. When female sterilization failure occurs, ectopic gestation is
more likely than intrauterine gestation, but the absolute likelihood of ectopic
pregnancy is actually lower than that associated with use of no method or even
IUDs.
Tubal sterilization is usually performed via an abdominal incision. A vaginal
approach offers the advantage of producing no visible scar, but such a procedure
increases the risk of pelvic infection and thus is used less frequently. The
fallopian tubes may be blocked by tying (with or without removal), by coagula-
tion, using unipolar or bipolar current, or by mechanical occlusion with silastic
bands or clips. All procedures except conventional laparotomy can be safely
performed using local anesthesia, thus avoiding the hazards inherent in the use of
general anesthesia.
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CONTRACEPTIVE BENEFITS AND RISKS 49
Studies suggest that tubal sterilization is a remarkably safe surgical procedure.
The case-fatality rate has been reported as low as 4 per lOO,OOO procedures in
U.S. hospitals (Peterson et al., 1982) but as high as 19 per 100,000 procedures in
Bangladesh (Grimes et al., 1982~. Most deaths are caused by complications
related to use of anesthesia, even when general anesthesia is not used Deaths
have occurred from hemorrhage and thermal injury as well (Peterson et al., 1983~.
Reports regarding nonfatal complications vary. In general, such studies indicate
that major morbidity is uncommon and vanes by surgical approach, anesthetic
technique, and tubal occlusion method.
No important long-term negative physiological effects of tubal sterilization
have been reported in the literature. Much concern has focused on menstrual
abnormalities, the so-called post-tubal syndrome, which was identified by a
number of studies prior to 1980. These early studies had methodological prob-
lems; better designed, more recent studies have found no evidence of a post-tubal
syndrome. When menstrual changes did occur, about as many women expen-
enced improvement in symptoms as experienced a deleterious change (Bhiwand-
iwala et al., 1983~. Many of the observed changes were attributable to cessation
of OC or IUD use. Studies have found conflicting results on the question of an
increased risk of hysterectomy following sterilization. It has been postulated that
any observed correlation may be explained by the fact that, once a woman has
been sterilized, either she or her physician may more quickly resort to surgical
management of any gynecologic problem.
Male sterilization, or vasectomy, is the cutting or occluding of the vas deferens
to prevent sperm transport. Although safe, simple, and highly effective, vasec-
tomy is not popular in most countries. Most users reside in the United States, the
United Kingdom, China, and India. Access to services and motivational factors
have been cited as reasons for the generally low level of use. Few studies report
any pregnancies after vasectomies and, of those that do, most have reported
failure rates below 1 percent, with most failures attributable to unprotected
intercourse shortly after vasectomy or spontaneous rejoining of the vas (Trussell
and Kost, 1987~.
The procedure consists of isolating the vas deferens, Men occluding it by
ligation (the most common approach), coagulation, or clip application. Local
anesthesia without premedication is most often used The risk of death attribut-
able to vasectomy is extremely low. The Association for Voluntary Surgical
Contraception has recorded only two vasectomy-related deaths associated with
over 160,000 procedures in programs it supported (Ross et al., 1985~.
Research has consistently failed to identify long-term health risks attributable
to vasectomy. In contrast to animal findings, at least six epidemiologic studies in
humans, including a large study in China, have indicated that the risk of myocar-
dial infarction is not increased in the 10 years following vasectomy (Goldacre et
al., 1978, 1979; Walker et al., 1981; Petitti et al., 1982; Massey et al., 1984; Perrin
et al., 1984~. Possible relationships between vasectomy and prostatic disease
have been examined (Sidney, 1987; Ross et al., 1985~. With the exception of one
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50 CONTRACEPTION ED REPRODUCTION
recent study (Honda et al., 1988), no association between vasectomy and prostatic
disease has been found, and a plausible alternative explanation for the results was
made by the authors of that study. Still controversial is the relationship between
vasectomy and subsequent genito-urinary tract diseases, such as kidney stones
(urolithiasis). One recent report has found a 70 percent increased risk of kidney
stones among men who had undergone vasectomy (Kronmal et al., 1988~. Other
studies have found no relationship, but the possibility warrants further evaluation.
TRADITIONAL METHODS
Traditional methods of contraception include periodic abstinence or rhythm,
withdrawal, douche, or complete abstinence. Unsupplemented breastfeeding on
demand postpones the onset of ovulation and may thus also be considered a form
of contraception. It is difficult to measure the use of these methods, since they
may be practiced without being called contraception. The United Nations reports
that over 77 million women rely on one of these methods United Nations, 1989~.
Periodic abstinence and withdrawal are much less effective than most of the
modem methods already discussed, with failure rates around 15-20 percent in the
first year of use (Trussell and Kost, 1987~.
That breastfeeding can provide considerable protection against pregnancy is
well documented (see Hatcher et al., 1988, for a review). Pregnancy rates in
populations depend on breastteeding prevalence and practices. Hatcher et al.
(1988:117) conclude: "Breastfeeding can be an effective method of fertility
control for a population, but breastfeeding effectiveness is unpredictable for the
individual woman, particularly with western patterns of breastfeeding and supple-
mentation."
Periodic abstinence or rhythm is based on awareness of variation in the
woman's fecundity over the menstrual cycle using the calendar, basal body
temperature, and/or the character of cervical mucus. Rhythm has no health risks
or noncontraceptive benefits for a woman. There may be an increased risk that an
old, rather than a fresh, egg will be fertilized, possibly leading to a higher risk of
fetal wastage or birth defects. Animal studies have shown that aged gametes may
be associated with increased early abortions and increased birth defects, and
equivocal, limited data suggest an increase in spontaneous abortions. But studies
on"humans have been unconvincing, either to support or discount the possible
effects (Hatcher et al., 1988; Kambic et al., 1988~.
It is uncertain how frequently coitus interruptus (withdrawal) is used world-
wide. There are no known biological side effects. Douching and other means of
cleaning out the vagina after intercourse have been used to prevent conception
ever since it was understood that ejaculation into the vagina caused pregnancy.
Not only is the method highly ineffective for contraception, but it also greatly
increases the risk of vaginal infection. Douching has been associated with an
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CONTRA CEPTiVE BENEFITS AND RISKS 51
increased risk of PID, although the relationship may not be causal. A case-control
study found that women who douched frequently had 4.4 times the risk of ectopic
pregnancy (Chow et al., 1985~.
DIMENSIONS OF NEW RESEARCH
Clearly, no modern method of contraception is completely free of health
consequences, whether adverse or beneficial or both. Oral contraceptives, which
increase the risk of a variety of cardiovascular problems, also protect against PID,
ectopic pregnancy, and two cancers of the reproductive system. Barrier methods
of contraception, which may reduce the transmission of sexually transmitted
diseases, are also associated with an increased risk of pregnancy. Sterilization,
while generally an extremely safe procedure, can be dangerous if improperly
performed.
Priorities for further safety studies should be determined by the incidence of
serious disease in a country. For example, where liver cancer is already problem-
atic, contraceptive research should focus on the impact of contraceptive methods
on this disease. At the same time, research must respond to case reports that are
particularly unusual. A finding that 9 out of 10 cases of a rare disease were all
using the same method of contraception would indicate the need for further study.
These decisions are far from simple. The pervasive concerns and worries of a
population or a government cannot be ignored, even when empirical data negate
their importance. Still, we are left with a number of questions. At what level of
incidence does an epidemiologic study become necessary? What level of risk is
acceptable for the continued marketing of a specific method? How important are
discomforting but nonfatal side effects?
Ongoing research to test new variations of existing contraceptive methods as
well as the development of new methods must be continued. The long-term
effects of most methods can be determined only after many years of use, a
situation that mandates repeated and protracted study. Cohort studies are needed
to evaluate the overall pattern of mortality and morbidity related to contraceptive
use, and case-control studies are needed to evaluate the contraceptive-related risks
for specific diseases. Moreover, ongoing surveillance of the use of all hormonal
contraceptives in both developed and developing countries is crucial.
By way of conclusion, it is appropriate to put the various risks of contraceptive
use into perspective. Due to the uncertainty associated with the venous health
risks for each method of contraception and the methodological complexities
inherent in such analyses, no definitive overall risk can be calculated by method
(see Ory et al., 1983, for estimates of risks). However, in developing countries,
where maternal mortality is high, and diseases associated with contraception such
as myocardial infarction are uncommon, there is no questions that contraception
is safer than pregnancy and childbirth.
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52 CONTRACEPTION kD REPRODUCTION
Any decision regarding contraceptive use must be based not only on the
noncon~aceptive risks and benefits, but also on the efficacy of the method. Each
individual's life situation and the level of risk particular to his or her characteris-
iics must be considered as well. Finally, the life consequences of childbearing for
the mother and child must also be considered. We now turn to the health
consequences of controlled fertility for children, again with special consideration
of high-risk categories.
Representative terms from entire chapter:
cervical cancer
