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Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×

D Tables of Odds Ratios: Supplement to Chapter 3

Carol J.R. Hogue

Member, Committee on Unintended Pregnancy

Chapter 3 includes an assessment of the literature published within the last 30 years that addresses various health and health-related consequences of unintended pregnancy. The literature base for most consequences studied does not permit a numerical survey. However, some effects, particularly ones related to pregnancy and pregnancy outcome, have been studied sufficiently to permit a structured assessment. These consequences include timing of the initiation of prenatal care, an estimate of the adequacy of prenatal care based on both timing and the number of visits, exposure of the fetus to smoking and alcohol, and the incidence of low birthweight (<2,500 grams) among live-born infants. A graphical presentation of studies on these issues is provided in Chapter 3.

This appendix provides more detail regarding those studies. To be included in this structured assessment, an investigation had to compare outcomes between women reporting intended conceptions and women reporting unintended conceptions, variously defined. When unintended was subdivided into mistimed and unwanted, estimates of effects (usually odds ratios) are included for both categories of unintended conception. An odds ratio is an estimate of the relative risk, that is, the risk of a poor outcome among the "exposed" group (unintended conception) relative to the risk of a poor outcome among the "unexposed" group (intended conceptions). These results, with 95 percent confidence intervals, are shown in column 5 of the tables in this appendix. The results in Figures 3-3 through 3-5 of Chapter 3 were selected from these results. If a study calculated both a crude and an adjusted odds ratio, only the adjusted one was included in the figure. When the results were available for both mistimed and unwanted conceptions, they were included in the figures. The references for this appendix are provided in Chapter 3.

Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×

TABLE D-1 Studies of Prenatal Care Attainment Associated with Pregnancy Intention

Definition of Intention

Population/Sample

Retrospective/Prospective

Control Factors

Results

Reference/Comments

Initiation of Prenatal Care (PNC) after the First Trimester

 

 

 

Unwanted:

(a) at conception, (b) at fourth month,

(c) in last trimester

120 black women, Boston City Hospital, married with at least one living child, 1964

Prospective at three points during gestation

None

Late PNC, (a) ORa = 2.89 (0.96,9.02)c, (b) OR = 3.57 (1.38,9.36)c , (c) OR = 2.42 (0.65,9.31)c

Watkins, 1968; (a) 77.5%, (b) 27.9%, (c) 11.7%            

(a) Mistimed, (b) unwanted

NSFG, 1982 (random sample of U.S. women 15–44, with live births 1979–1982)

Retrospective (œ3 yrs. postpartum)

Race

(a) RRb, all = 1.6c; RR, white = 1.6c; RR, black = 1.4c (b) RR, all = 1.8c; RR, white = 1.7c; RR, black = 1.75c

Pamuk and Mosher, 1988            

"Intended" vs. "unintended"

NNS, 1980 (random sample of U.S., married)

Retrospective (>6 mo postpartum)

Race, residence, education, birth order

Crude OR = 1.25c Adjusted OR = -1.19c

Wells et al., 1987            

Planned vs. unplanned

416, central Harlem residents in PNC, 1982–1983

Retrospective (at first PNC visit)

None

OR = 1.31c

McCormick et al., 1987; 73% were unplanned

Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×

Definition of Intention

Population/Sample

Retrospective/Prospective

Control Factors

Results

Reference/Comments

Intended (stopped using contraception because of pregnancy desire or just before pregnancy, wanted to become pregnant) vs. unintended

NLSY, 1984, women 18–26, nationally representative sample of 6,015

Retrospective (78%), prospective (22% during pregnancy)

Race, economically disadvantaged (white), southern or urban resident at age 14, grandmother's education, maternal age

For unintended, crude RR = 1.14c; adjusted OR = 1.6c

Marsiglio and Mott, 1988; they used the term "wanted" but the questions more closely reflect intended            

"Intended" vs. "unintended"

Random sample, 1,490; births in England, 1,984

Retrospective (>4 mo postpartum)

None

Risk of entry after first trimester; OR = 1.9 (1.33,2.17)c

Cartwright, 1988; interview asked pregnancy intention            

(a) Mistimed, (b) unwanted

NMIHS, 1988 nationally representative sample of 9,953

Retrospective (at least 1 yr postpartum)

None

(a) RR = 2.88c (b) RR = 2.62c

Kost et al., 1994            

(a) Mistimed, (b) unwanted

Oklahoma PRAMS, 1988–1993, (a) N = 2,329 (b) N = 933

Retrospective (4–12 mo postpartum)

Age, education, source of family income, timing of pregnancy recognition, parity

(a) Crude OR = 2.7 (2.1,3.4); adjusted OR = 1.4 (1.04,1.9) (b) crude OR = 4.6 (1.3,6.1); adjusted OR = 1.7 (1.1,2.5)

DePersio et al., 1994            

Planned vs. "surprise"

Hispanic, Houston, TX, public hospital patients, 100 each entered PNC in 1st, 2nd, 3rd trimester or none

Retrospective (at delivery)

None

Risk of entry after first trimester OR = 2.64 (1.50,4.66)c

Byrd, 1994; early PNC associated with hospital access card, fewer perceived barriers, more benefits to baby            

Inadequate Prenatal Care (PNC)

 

 

 

 

See Results column

Random sample in Oklahoma, births, 1985

Retrospective (at delivery)

Multiple

Receipt of inadequate care, mistimed, family support OR = 1.15c (NS); mistimed, pregnancy discussed OR = 1.09c (NS); unwanted, family support, OR = 1.15c (NS); unwanted, pregnancy discussed, OR = 1.36 (p < 0.05)

St. John and Winston, 1989; see text            

Unwanted

Case—control study, three sites in Missouri; adequate, N=720; inadequate, N=764

Retrospective (at delivery)

Multiple

Receipt of inadequate care; OR = 1.39 (1.11, 1.67)

Sable, 1992; 74% of women with inadequate care had not wanted the pregnancy

Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×

Complete Table on previous page.

Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×

Definition of Intention

Population/Sample

Retrospective/Prospective

Control Factors

Results

Reference/Comments

Initial attitude: negative, mixed, or positive

200 poor, mainly black women, Detroit, MI

Retrospective (at delivery)

Attitudinal

Zero-order correlation = 0.39 (p < 0.05)

Poland et al., 1990            

Planned vs. unplanned; somewhat/very unhappy vs. neutral/happy

Case—control, 400 inadequate care, 100 adequate care, Mecklenburg, NC, 1990–991

Retrospective (at delivery)

None

For unplanned, OR = 1.86 (1.10,3.18)c for unhappy, OR = 2.2 (0.96,3.70)c

Boggs and Miles, 1991; among cases with inadequate care, 81% unplanned and 21.2% unhappy            

(a) Mistimed, (b) unwanted

Oklahoma PRAMS, 1988–1993 (a) N = 2,092 (b) N = 810

Retrospective (4–12 mo postpartum)

Education, marital status, source of family income, timing of pregnancy initiation, parity

(a) crude OR = 2.7 (1.9,3.7); adjusted OR = 1.3 (0.8,1.9) (b) crude OR = 5.5 (3.8,8.0); adjusted OR = 1.9 (1.2,3.1)

DePersio et al., 1994

NOTE: NSFG (National Survey of Family Growth); NNS (National Natality Survey); NLSY (National Longitudinal Survey of Youth); NMIHS (National Maternal and Infant Health Survey); PRAMS (Pregnancy Risk Assessment Monitoring System); NS (not significant).

a  

The OR (odds ratio) is the odds of adverse outcome among exposed persons relative to the odds among unexposed persons.

b  

The RR (relative risk) is the risk of the adverse outcome among exposed persons relative to the risk among unexposed persons. Relative risk and odds ratios are similar when adverse outcome is rare.

c  

Calculated for this report.

Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×

TABLE D-2 Studies of Behavioral Risk Factors for Low Birthweight or Preterm Delivery Associated with Pregnancy Intention

Definition of Intention

Population/Sample

Retrospective/Prospective

Control Factors

Results

Reference/Comments

Smoking

 

 

 

 

 

''Intended" vs. "unintended"

NNS, 1980 (random sample of U.S. married women)

Retrospective (> 6 mo post-partum)

Race, residence, education, birth order, early PNC

Whether didn't stop smoking: crude ORa = 1.13c; adjusted OR = 1.07c

Wells et al., 1987; early PNC had similar but independent impact on smoking cessation, as planning the pregnancy did            

Planned vs. unplanned

416, central Harlem residents in PNC, 1982–1983

Retrospective (at first PNC visit)

None

OR = 1.08c

McCormick et al., 1987; 41% smoked during pregnancy            

(a) Mistimed, (b) unwanted

NSFG, 1982 (random sample of U.S. women ages 15–44, with live births 1979–1982)

Retrospective (3 yr postpartum)

Race

(a) RRb, all = 1.3c RR, white = 1.25c RR, black = 1.05c (b) RR, all = 1.3c RR, white = 1.4c RR, black = 1.2c

Pamuk and Mosher, 1988

Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×

Definition of Intention

Population/Sample

Retrospective/Prospective

Control Factors

Results

Reference/Comments

"Intended" vs. "unintended"

Random sample, 1,490; births in England, 1,984

retrospective (>4 mo postpartum)

Social class

Smoking OR = 1.66 (1.25,2.22)c

Cartwright, 1988; interview asked pregnancy intention            

Intended (stopped using contraception because of pregnancy desire or just before pregnancy, wanted to become pregnant) vs. unintended

NLSY, 1984, women 18–26, nationally representative sample of 6,015

Retrospective (78%) and prospective (22% during pregnancy)

Race, economically disadvantaged (white), southern or urban resident at age 14, grandmother's education, maternal age

For unintended, crude RR = 1.04c; adjusted OR = 0.97c

Marsiglio and Mott, 1988; they used the term "wanted" but the questions more closely reflect intended            

(a) Mistimed, (b) unwanted

NMIHS, 1988, nationally representative sample of 9,953

Retrospective (at least 1 yr postpartum)

Marital status

(a) Crude RR = 1.71c (b) crude RR = 1.47c

Kost et al., 1994; smoked during pregnancy; married women with wanted conception smoked much less than other subgroups            

(a) Mistimed, (b) unwanted

Oklahoma PRAMS, 1988–1993 (a) N = 2,267 (b) N = 900

Retrospective (4-12 mo postpartum)

Age, education, race, martial status, source of family income

(a) Crude OR = 1.3 (1.02, 1.6); adjusted OR = 1.0 (0.8,1.3) (b) crude OR = 2.4 (1.9, 3.1); adjusted OR = 1.8 (1.3,2.4)

DePersio et al., 1994; smoking 3 mo before delivery            

Alcohol

 

 

 

 

 

Planned vs. unplanned

416, central Harlem residents in PNC, 1982–1983

Retrospective (at first PNC visit)

None

OR = 2.67c

McCormick et al., 1987; 9.2% drank during pregnancy

Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×

Complete Table on previous page.

Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×

Definition of Intention

Population/Sample

Retrospective/Prospective

Control Factors

Results

Reference/Comments

Intended (stopped using contraception because of pregnancy desire or just before pregnancy, wanted to become pregnant) vs. unintended

NLSY, 1984, women aged 18-26, nationally representative sample of 6,015

Retrospective (78%), prospective (22% during pregnancy)

Race, economically disadvantaged (white), southern or urban residents at age 14, grandmother's education, maternal age

For unintended, crude RR = 1.05c; adjusted OR = 1.25c

Marsiglio and Mott, 1988; they used the term "wanted," but the questions more closely reflect intended            

(a) Mistimed, (b) unwanted

NMIHS, 1988, nationally representative sample of 9,953

Retrospective (at least 1 yr postpartum)

None

(a) RR = 1.11c

(b) RR = 1.77c

Kost et al., 1994; drank one or more times per week

NOTE: NNS (National Natality Survey); NSFG (National Survey of Family Growth); NLSY (National Longitudinal Survey of Youth); PRAMS (Pregnancy Risk Assessment Monitoring System); NMIHS (National Maternal and Infant Health Survey).

a  

The OR (odds ratio) is the odds of adverse outcome among exposed persons relative to the odds among unexposed persons.

b  

The RR (relative risk) is the risk of the adverse outcome among exposed persons relative to the risk among unexposed persons. Relative risk and odds ratios are similar when adverse outcome is rare.

c  

Calculated for this report.

Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×

TABLE D-3 Studies of Low Birth Weight (LBW) (<2,500 grams) Associated with Pregnancy Intention

Definition of Intention

Population/Sample

Retrospective/ Prospective

Control Factors

Results

Reference/ Comments

Wanted vs. unwanted

17 selected U.S. sites, 1971–1972; 4,891 white and 3,030 black women

Retrospective (at delivery)

Race

Crude ORa = 1.2c OR for whites = 1.36c OR for blacks = 0.94c

Morris et al., 1973; women with high education and unwanted conceptions had babies with significantly higher LBW rates                

Intended (stopped using contraception because of pregnancy desire or just before pregnancy, wanted to become pregnant) vs. unintended

NLSY, 1984, women ages 18–26, nationally representative sample of 6,015

Retrospective (78%) and prospective (22% during pregnancy)

Race, economically disadvantaged (white), southern or urban resident at age 14, grandmother's education, maternal age

For unintended, crude RRb = 1.3c; adjusted OR = 0.92c adjusted OR = 0.88c (including behavioral risk factors)

Marsiglio and Mott, 1988                

(a) Mistimed, (b) unwanted

NSFG, 1982 (random sample of U.S. women aged 15–44, with live births 1979–1982)

Retrospective (œ 3 yr post-partum)

Race

(a) RR, all = 1.4c RR, white = 1.2c RR, black = 1.3c

Pamuk and Mosher, 1988

Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×

Definition of Intention

Population/Sample

Retrospective/ Prospective

Control Factors

Results

Reference/ Comments

Unintended vs. intended

Case-control study, 1984; 83 LBW cases, 1,392 NBW controls

Retrospective (at delivery)

Smoking

Crude OR = 1.28c adjusted OR = 1.17c (0.70, 1.95)c

Cartwright, 1988                

Wanted vs. unwanted

1,518 multiparous, indigent women in Birmingham, AL, 1985–1988, with risk of IUGR

Prospective (at PNC visit)

None

OR = 1.3c

Goldenberg et al., 1991; sample was limited to women receiving early PNC                

Mistimed, unwanted

1988 NSFG, most recent singleton birth

Retrospective (< 5 yr post-partum)

Smoking, race

Reduction in LBW if all unwanted conceptions had been avoided

Kendrick et al., 1990; mistimed not associated with LBW

 

 

 

 

 

No.

% change

 

 

 

 

 

Black

69,000

7

 

 

 

 

 

White

67,000

4

 

 

 

 

 

Smoker

70,000

6

 

 

 

 

 

Non- smoker

66,000

7

 

(a) Mistimed, (b) unwanted

NMIHS, 1988, nationally representative sample of 9,953

Retrospective (at least 1 yr postpartum)

None

(a) Crude RR = 1.21c

(b) crude RR = 1.80c

Kost et al., 1994                

(a) Mistimed, (b) unwanted

Oklahoma PRAMS, 1988–1993 (a) N = 2,215 (b) N = 888

Retrospective (4–12 mo postpartum)

Education, black race, marital status at delivery, smoking three months before delivery, trimester that PNC began, infant gender, parity, plurality

(a) Crude OR = 1.2 (1.1,1.4); adjusted OR = 1.0 (0.8,1.1) (b) crude OR = 1.4 (1.2,1.6); adjusted OR = 0.9 (0.7,1.1)

DePersio et al., 1994                

(a) Mistimed, (b) unwanted

1990 NICHD/MOMIH survey

Retrospective (>6 mo postpartum)

Multiple

(a) No increased risk (b) crude OR = 1.44 for LBW adjusted or NS VLBW not associated

Sable, 1992

NOTE: NLSY (National Longitudinal Survey of Youth); NBW (Normal birthweight is over 2,500 grams); IUGR (intrauterine growth retardation); NSFG (National Survey of Family Growth); NMIHS (National Maternal and Infant Health Survey); PRAMS (Pregnancy Risk Assessment Monitoring System); NICHD/MOMIH (National Institute of Child Health and Development/Missouri Mothers and Infant Health); VLBW (very low birthweight is under 1,500 grams)

a  

The OR (odds ratio) is the odds of adverse outcome among exposed persons relative to the odds among unexposed persons.

b  

The RR (relative risk) is the risk of the adverse outcome among exposed persons relative to the risk among unexposed persons. Relative risk and odds ratios are similar when adverse outcome is rare.

c  

Calculated for this report.

Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×

Complete Table on previous page.

Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×
Page 296
Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×
Page 297
Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×
Page 298
Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×
Page 299
Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×
Page 300
Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×
Page 301
Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×
Page 302
Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×
Page 303
Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×
Page 304
Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×
Page 305
Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×
Page 306
Suggested Citation:"D Table of Odds Ratios." Institute of Medicine. 1995. The Best Intentions: Unintended Pregnancy and the Well-Being of Children and Families. Washington, DC: The National Academies Press. doi: 10.17226/4903.
×
Page 307
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Experts estimate that nearly 60 percent of all U.S. pregnancies--and 81 percent of pregnancies among adolescents--are unintended. Yet the topic of preventing these unintended pregnancies has long been treated gingerly because of personal sensitivities and public controversies, especially the angry debate over abortion. Additionally, child welfare advocates long have overlooked the connection between pregnancy planning and the improved well-being of families and communities that results when children are wanted.

Now, current issues--health care and welfare reform, and the new international focus on population--are drawing attention to the consequences of unintended pregnancy. In this climate The Best Intentions offers a timely exploration of family planning issues from a distinguished panel of experts.

This committee sheds much-needed light on the questions and controversies surrounding unintended pregnancy. The book offers specific recommendations to put the United States on par with other developed nations in terms of contraceptive attitudes and policies, and it considers the effectiveness of over 20 pregnancy prevention programs.

The Best Intentions explores problematic definitions--"unintended" versus "unwanted" versus "mistimed"--and presents data on pregnancy rates and trends. The book also summarizes the health and social consequences of unintended pregnancies, for both men and women, and for the children they bear.

Why does unintended pregnancy occur? In discussions of "reasons behind the rates," the book examines Americans' ambivalence about sexuality and the many other social, cultural, religious, and economic factors that affect our approach to contraception. The committee explores the complicated web of peer pressure, life aspirations, and notions of romance that shape an individual's decisions about sex, contraception, and pregnancy. And the book looks at such practical issues as the attitudes of doctors toward birth control and the place of contraception in both health insurance and "managed care."

The Best Intentions offers frank discussion, synthesis of data, and policy recommendations on one of today's most sensitive social topics. This book will be important to policymakers, health and social service personnel, foundation executives, opinion leaders, researchers, and concerned individuals. May

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