Contraceptive Use and Controlled Fertility Health Issues for Women and Children (1989) / Chapter Skim
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Mechanisms for the Association of Maternal Age, Parity, and Birth Spacing With Infant Health
Mechanisms for the Association of Maternal Age, Parity, and Birth Spacing With Infant Health
Pages 96-139
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From page 96... ...
This is partly to help refine estimates of the effects of family planning programs on infant health and partly to identify promising leads for research and the design and targeting of future maternal and child health interventions. In a review of studies using data from the World Fertility Survey (WFS)
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From page 97... ...
266~. Family planning programs can affect the distribution of all three of these risk factors in the population and may thereby be an important tool in reducing infant mortality rates.
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From page 98... ...
the United States in 1983. Infectious and parasitic diseases account for a much larger proportion of the total when infant mortality rates are high.
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From page 99... ...
197~. This contrast is important in the present context because it indicates the relative size of the effects that would have to be present for a particular category of cause of death to account for the observed indirect relationships between biodemographic variables and infant mortality.
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From page 100... ...
In relative terms, prematurity3 accounts for a larger proportion of low birthweight infants in rich countries than in poor countries, where many more infants born at term are low in weight (Villar and Belizan, 1982~. The relative risk of infant mortality is much higher for the preterm Ban for the term-but-low-weight infant.
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From page 101... ...
In high-mormlity countries as well, infants born to young mothers are often at a disadvantage. In five of the Latin American project sites for the Inter-American Investigation of Mortality in Early Childhood in 1967-1970, infants born to mothers less than 20 years old were between 1.3 and 1.9 times as likely to die in the neonatal period as those born to mothers aged 20 to 24, and their relative risk was about as large for postneonatal deaths as well (Puffer and Serrano, 1973, Table 147~.
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From page 102... ...
present infant mortality rates from rural Mexico by mother's age and parity '(Table 4~. They show that the excess risk for infants born to mothers less than 20 years old was for the second and third infants.
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From page 103... ...
I suspect that the 20- to 24year-old primiparae represented in the rural Mexican data include a large number of women who had prior miscarriages. The lowest infant mortality rates in this high-fertility population, in fact, are found along the diagonal of the table: these represent the women who are having the `'right" number of live births for their age group.
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From page 104... ...
The association between first-birth order and low birthweight persisted in a multivariate analysis controlling for family income and other social characteristics, while the association between young maternal age and low birthweight disappeared in the multivariate analysis. In an analysis of determinants of infant mortality using the same data, younger maternal age (below 18 years)
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From page 105... ...
showed that infants born to very young (10- to 16-year-old) black mothers had low birthweights and lengths, which he suggested could be explained by the "fetal-maternal competition for nutrients." And in an analysis of data on infants of very young black mothers in New Orleans, Cherry et al.
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From page 106... ...
It is known that children in poor communities, where undernutrition and infectious diseases are prevalent, are shorter than those of similar genetic background who have had less stress, at least until the age of 7 or so. But adults in poor countries (e.g., West Africa)
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From page 107... ...
Pregnancy-Induced Hypertension Pregnancy-induced hypertension (PIH) is associated with premature delivery and placental abruption, both of which are associated with low birthweight (Niswander, 1977~.7 In the 1958 British Perinatal Mortality Study it was found that 18 percent of infants born to mothers diagnosed as having pre-eclampsia (PIH and edema)
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From page 108... ...
had perinatal mortality rates comparable to those of the normotensive women; the excess rate for hypertensives was due to higher death rates for infants born to women with pre-eclampsia and chronic hypertension. This underlines the heterogeneity of the "high blood pressure during pregnancy" population.
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From page 109... ...
in poor countries because they often present at hospitals only after convulsions have begun. The lack of adequate antenatal care in many places could lead to a detection bias that makes it difficult to interpret statistics based on hospital births: higher rates of pregnancy complications among young women may be due to differences among age groups in the likelihood of an uncomplicated delivery taking place in a hospital as well as to true differences in the prevalence of complications.
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From page 110... ...
Neither the causes of the parity difference in infection rates nor its implications for stillbirth rates, infant growth, and infant mortality are clear. Nonetheless, McGregor (1984)
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From page 111... ...
Obstetric management of breech presentation is probably more aggressive for primiparae, but of course many of the poorest women have no access to facilities that can perform a safe caesarean section. Thus breech presentation may be more common for grand multiparae, but higher case-mortality rates for primiparae would lead to a parity differential, probably small, in infant mortality.
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From page 112... ...
Older primiparae in poor countries are usually a very select group, however, including many women who aborted previous pregnancies, so it is difficult to separate the effects of age from those of fecundity and other woman-specific factors not easily measured in the data available to demographers. Even if one concludes that the associations between young maternal age and infant mortality are not true age effects, it may still be true that family planning programs could affect infant health by lowering the percentage of births to adolescents.
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From page 113... ...
This and a more direct selection effect caused by purposeful efforts to replace children who have died complicate the interpretation of infant mortality rates at high parity. The British Perinatal Mortality Survey of all pregnancy outcomes in a period during 1958 showed a U-shaped association of rates of both low-birthweight and preterm births with parity (Table 6~.
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From page 114... ...
. In the Collaborative Perinatal Study in the United States, higher-parity infants were at much higher risk of death both in the perinatal and neonatal periods (though the neonatal mortality differential associated with parity was much smaller for blacks than for whites)
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From page 115... ...
In both birthweight categories, perinatal death rates for infants of parities 4 and over were well below those for first-parity infants if no prior loss was reported and well above those for h~rst-parity infants when there was a prior loss. Adjustments for maternal characteristics and adequacy of prenatal care made these differences even starker.
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From page 116... ...
For intrapartum deaths there was no risk difference by maternal age. Infants born to mothers over 35 were at increased risk for perinatal deaths attributable to congenital abnormalities (relative risk of 1.54 compared with infants born to women aged 25 to 29~.
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as for chromosomal abnormalities (Hansen, 1986~. Iron-Deficiency Anemia and Micronutrient Deficiencies The main way in which maternal anemia could affect infant health is through an association with premature delivery.
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From page 118... ...
Twins are more likely than singletons to be born prematurely and to be of low weight for gestational age. They also suffer higher infant mortality rates.
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From page 119... ...
, perhaps due to the associations with hypertension discussed above. Conclusions Most of the studies that have shown excess risks of morbidity and mortality for infants born to older mothers or those at very high parity have used data from countries with low infant mortality rates, mainly in Europe and North America.
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From page 120... ...
The effect of family planning programs on infant mortality rates through reduced numbers of births to older women and high-parity births would presuma
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From page 121... ...
, for example, found a U-shaped relationship between length of the preceding interval between births and infant mortality rates in rural Mexico, with rates declining as internals increased and then rising again after intervals of 4 years (Table 11~. Both neonatal and postneonatal infant mortality rates were higher for the shorter intervals: infants born 12 to 23 months after a live birth had neonatal mortality rates 1.6 times as high, and postneonatal mortality rates 1.5 times as high, as for infants born 24 to 35 months after a live birth.
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From page 122... ...
. As is true for the associations of maternal age and parity with infant mortality, the association of short interbirth intervals with infant mortality may be due in part to confounding variables, social characteristics of families that affect both the interbirth intervals and the risk of mortality independently.
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From page 123... ...
Unless short intervals caused the premature deliveries, reducing the number of short intervals would do nothing to lower infant mortality rates. But this view is contradicted by evidence that short intervals are associated with low b~hweight and higher risk of infant mortality even when gestaiional age is held constant.
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From page 124... ...
Table 12 shows that even within gestational-age categories infants born after a short preceding interval weigh less. In an analysis of prospective data from the Narangwal experiment in the Punjab, Fleming and Gray (1988)
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From page 125... ...
The energy cost of lactation is greater than that of pregnancy, so one would expect that the provision of nutrients to the first child of a closely spaced pair directly competes with the provision of nutrients to the second fetus ARC, 1981~. Few of these causal pathways have actually been traced in human supplementation trials, and there is a good deal of disagreement in the interpretation of results from human supplementation trials and animal experiments concerning the ways in which fetal growth is constrained below genetic potential.
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From page 126... ...
The relative risk of IUGR was 1.38 for the infants born after a short interval, controlling for maternal age, education, smoking, and previous fetal loss or low birthweight. The relative risk was lowered somewhat, and lost statistical significance, when maternal prepregnancy weight was also controlled, which suggests that IUGR was caused by the maternal malnutrition associated with too short a recuperative period after the preceding pregnancy.
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From page 127... ...
However, Millman and Cooksey (1987) found that little of the association between short birth intervals and increased risk of infant mortality for the second infant of the pair could be accounted for by the addition of information on breastEeeding.
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From page 128... ...
account for the majority of infant deaths in high-mortality countries (Chen, 1983~. It is not necessary, but certainly likely, that many of the excess infant deaths associated with extremes of maternal age or parity and with short birth intervals have infections as a proximate cause.
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From page 129... ...
and preterm labor in general pose a severe risk of infant mortality. Infants born after PROM are at increased risk of neonatal infections, perinatal asphyxia, and respiratory distress syndrome [though for the latter the risk associated with PROM is less than that associated with other types of premature labor (Blackmon et al., 1986~.
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From page 130... ...
Unnary tract infections, very common in poor countries and among poor people in rich countnes, are associated with a sharply increased likelihood of low birthweight (due to prematurity, IUGR, or bother Sever et al.
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From page 131... ...
found infant mortality to be higher in households with more than 10 members than in smaller households a relative risk of 1.5 in an analysis controlling for several other economic and demographic variables (Rahman et al., 1985~. In this sample, the authors argue, such large households tend to have more than two adult earners and thus are not poorer than smaller households, thus reversing one effect that confounds crude household-size mortality differentials in other samples.
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From page 132... ...
and a true causal chain inadequate recuperation from the first partuntion, leaving structures too weak to support the next pregnancy. The WFS studies have found short intervals to be associated with an excess risk that continued well past early infancy, but this is consistent with both prematurity and fetal growth retardation as causal mechanisms, since infants born too small and too early who survive the neonatal period may still have respiratory and immunologic problems that weaken them later.
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From page 133... ...
Ashword~ 1987a Infant mortality in southern Brazil: a E-aiion-based study of causes of death. Archi~cs of Diseases in Childhood 62:487~90.
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From page 134... ...
1987 Does family planning reduce infant mortality rates? Population and Development Review 13:323-334.
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From page 135... ...
_~~ 135 ~_ 1983 we ^= ~ ~ ~ ~ sit ad it wait By.
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From page 136... ...
C Cooksey 1987 Birth weight and the effects of birth spacing and breastfeeding on infant mortality.
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From page 137... ...
Placek, P 1977 Maternal and infant health factors associated with low infant birth weight: findings from the 1972 National Natality Survey.
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From page 138... ...
M Belizan 1982 The relative contribution of prematurity and fetal growth mardaiion to low birth weight in developing and developed societies.
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From page 139... ...
World Health Statistics Quarterly 34:22~238. Wright, H
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