The intergenerational relationship between mother's birthweight, infant birthweight and infant mortality in black and white mothers

Summary. The relationship between the birthweight of white and black mothers and the outcomes of their infants were examined using the 1988 National Maternal and Infant Health Survey. White and black women who were low birthweight themselves were at increased risk of delivering very low birthweight (VLBW), moderately low birthweight (MLBW), extremely preterm and small size for gestational age (SGA) infants. Adjustment for the confounding effects of prepregnant weight and height reduced the risks of all these outcomes slightly, and more substantially reduced the maternal birthweight associated risk of moderately low birthweight among white mothers. There was little effect of maternal birthweight on infant birthweight-specific infant mortality in white mothers; however, black mothers who weighed less than 4 lbs at birth were at significantly increased risk of delivering a normal birthweight infant who subsequently died. Although the risks for the various outcomes associated with low maternal birthweight were not consistently higher in black mothers compared with white mothers, adjustment for prepregnant weight and height had a greater effect in white mothers than in black mothers. We suggest that interventions to reduce the risks for adverse pregnancy outcomes associated with low maternal birthweight should attempt to optimise prepregnant weight and foster child health and growth.     

Sex-specific associations of maternal birthweight with offspring birthweight in the Omega study

PurposeWe investigated nonlinear and offspring sex–specific associations of maternal birthweight (BW) with offspring BW among participants of the Omega study, a pregnancy cohort.MethodsMaternal BW was modeled as a continuous variable, linear spline and binary variable indicating low birthweight (LBW; <2500 vs. ≥2500 grams). Offspring BW was modeled as a continuous and binary variable in regression models. Nonlinearity was assessed using likelihood ratio tests (LRTs) in marginal linear spline models.ResultsFor every 100-gram increase of maternal BW, offspring BW increased by 22.29 (95% CI: 17.57, 27.02) or 23.41 (95% CI: 6.87, 39.96) grams among mothers with normal BW or born macrosomic, respectively, but not among LBW mothers (β = −8.61 grams; 95% CI: −22.88, 5.65; LRT P-value = .0005). For every 100-gram increase in maternal BW, BW of male offspring increased 23.47 (95% CI: 16.75, 30.19) or 25.21 (95% CI: 4.35, 46.07) grams among mothers with normal BW or born macrosomic, respectively, whereas it decreased 31.39 grams (95% CI: −51.63, −11.15) among LBW mothers (LRT P-value < .0001). Corresponding increases in BW of female offspring (16–22 grams) did not differ among mothers with LBW, normal BW or macrosomia (LRT P-value = .9163).ConclusionsMaternal and offspring BW associations are evident among normal BW and macrosomic mothers. These associations differ by offspring sex.     

Gestational age and intrauterine growth retardation among white and black very low birthweight infants: a population-based cohort study

Summary. Very low birthweight (VLBW) is a commonly used endpoint in perinatal epidemiology, but the population of VLBW infants comprises a wide range of gestational ages and rates of fetal growth. We used data from a population-based study of all 1072 black and white VLBW liveborn infants born in 29 counties in Georgia between April 1986 and March 1988. Less than 1% of the VLBW infants were ≥ 37 weeks gestation; most were 29–32 weeks (26%) or 25 to 28 weeks (40%); 12% were 22 weeks or less. All infants 33 weeks gestation or greater were growth retarded. The population of VLBW infants seems to comprise three groups: approximately 11% very immature infants of 22 weeks or less; the majority of infants, born between 23 and 30 weeks, 90% of which are of normal weight for their gestational age; and a group of less premature, growth-retarded infants from 31 to 36 weeks. We found little or no difference in the distribution of gestational age or the percentage of intrauterine growth rates (IUGR) between black and white infants. In the USA the VLBW rate among black infants is over three times greater than that among white infants and consequently the rates of the three types of VLBW among black infants are likely to be triple those among white infants.     

The relationship between maternal skinfold thickness, smoking and birthweight in black and white women

Summary. A prospective study was conducted in a sample of 1491 multiparous women to ascertain whether the relationship between maternal tricep skinfold thickness and infant birthweight is modified by smoking status and whether the relationship is different in white and black infants. Maternal tricep skinfold thickness measured at midpregnancy was a significant predictor of infant birthweight in both white and black infants after adjusting for gestational age at birth, maternal height, maternal age, parity, alcohol consumption and sex of the infant. However, maternal tricep skinfold thickness was a better predictor of birthweight in smokers compared with nonsmokers. Both white and black women with tricep skinfold thickness below the sample mean had lower infant birthweight than women with tricep skinfold at or above the mean, after adjusting for gestational age at birth, but the difference was greater in smokers (198 g for white and 221 g for black infants) than in nonsmokers (124 g for white and 120 g for black infants). These results suggest that maternal subcutaneous fat measured by tricep skinfold thickness has a greater effect on infant birthweight in smokers compared with nonsmokers, with similar effects in white and black infants.     

The association of maternal low birthweight and infant low birthweight in a racially mixed population

The association between maternal low birthweight (LBW) and infant low birthweight has been explored in previous studies in mainly middle and upper income, Caucasian populations. This study investigated whether the association found in these populations is true in a racially mixed, low socio-economic group. A case-control methodology was used and estimates of association were derived by means of logistic regression analyses. Data were gathered for 167 LBW infant-mother dyads and 338 adequate weight infant-mother controls matched on race and parity. The odds of a LBW infant having a LBW mother were 80% more likely than for adequate weight infants (OR = 1.80, 95% CI 1.14-2.84). This association was stronger for Hispanic women and their infants than for Black or non-Hispanic White women and their infants. Women who were both preterm and LBW had the higher estimate of risk for infant LBW than women who were LBW due to intrauterine growth retardation (IUGR). As found in previous research, the estimate of association between maternal LBW and infant LBW was greater for those infants who were LBW due to IUGR than those who were LBW due to being premature. The question of whether maternal LBW is also associated with increased risk of neonatal mortality and morbidity is as yet left unanswered.     

Risk of low birthweight and prematurity among foreign-born mothers.

Data collected during postnatal visits were used to study the risk of low birthweight (LBW) and prematurity among foreign-born mothers and mothers born in Canada. 2,913 singleton live births were included in the analysis. Odds ratios (OR) and 95% confidence intervals (CI) for LBW and prematurity were estimated using a logistic regression model. Foreign-born mothers did not have a higher risk of LBW or prematurity as compared to native-born mothers (OR = 1.1, 95% CI = 0.8-1.5; OR = 1.0, 95% CI = 0.7-1.4, respectively). For both LBW and prematurity, women in the intermediate category of length of stay (1-3 years) had a somewhat lower risk and women with the shortest length of stay (less than one year) had a slightly higher risk than women with the longest length of stay (more than 3 years). However, none of these results was statistically significant. Results of this study suggest that foreign-born mothers do not have a higher risk than Canadian-born mothers of bearing a LBW or premature infant. This finding differs from the widespread perception that immigrant mothers are at high risk for adverse birth outcomes.     

Effect of maternal age, smoking and deprivation on birthweight

Low birthweight is often used as a health indicator. This paper reports the findings of a cohort study, which were analysed to determine the relationship, if any, between the age of the mother and birthweight given the mother's smoking habits and the level of social deprivation of the mother's place of residence. The data used were extracted from those data routinely collected by the Information and Statistics Division of the National Health Service, Scotland. Information on 178,801 singleton live births occurring between 1992 and 1994 was used in the analysis. The factors considered were those available directly from the official records. The level of social deprivation was measured using Carstairs index based on the postcode sector. Although younger and older mothers have lighter babies, on average, it was found that this effect can be largely explained by differences in the smoking habits and level of deprivation of the mothers. Birthweight, adjusted for gestational age, sex of the baby and parity of the mother, was significantly lower for babies born to mothers who smoked during pregnancy. It is clear, however, that the detrimental effect of smoking increases with the age of the mother. Although adjusted birthweight was lower for those in areas of high deprivation, this effect is small compared with the effect of smoking. Any attempt to decrease the percentage of low-birthweight babies must focus on reducing the percentage of mothers who smoke.     

Paternal age as a risk factor for low birthweight

OBJECTIVES: We examined associations between paternal age and low birth-weight in the US urban population. METHODS: Using a population-based sample of 4621 births, we used multiple logistic regression analysis to estimate associations between paternal age and low birthweight, controlling for maternal age, other demographic factors, and the child's gender. RESULTS: When the child's gender and the mother's race/ethnicity, birthplace, parity, marital status, and health insurance type were controlled, teenaged fathers were 20% less likely and fathers older than 34 years were 90% more likely than fathers aged 20 to 34 years to have low-birthweight babies. The associations were significant when maternal age was also controlled. No racial/ethnic differences in associations between paternal age and low birthweight were found. CONCLUSIONS: We identified paternal age as an independent risk factor for low birthweight in the US urban population, suggesting that more attention needs to be paid to paternal influences on birth outcomes and to the interactive effects of urban environments and individual risk factors on health.     

Gestational duration and birthweight in white, black and mixed-race babies.

Using the 1983 United States population of single live births, birthweight and gestational duration were compared for babies of these different parental racial groups: both parents White, mother White-father Black, mother Black-father White, both parents Black. The four groups differed significantly with respect to the usual sociodemographic variables. Mean birthweight and mean gestational duration decreased in that order from the White-White reference group, and conversely there were increasing trends for low birthweight and preterm delivery. Adjustment for the usual sociodemographic variables did not alter these trends appreciably. Group differences were more strongly related to the mother's race than to the father's, and the trends were related to the mother's race. Because the father's race was significant, genetic factors are probably of some importance. The evidence from this study, together with the often-demonstrated relationships between low birthweight and preterm delivery with sociodemographic variables, and the short-term downward secular trends in low birthweight, support the concept that non-genetic maternal factors are more important for these abnormal outcomes. But because neither the usually utilised sociodemographic variables nor genetic factors seem to explain much of the group differences, new approaches are necessary to understand why, irrespective of ethnic group, some women are at excess risk for suboptimal birth outcome.     

Ten-year changes in birthweight distributions of black and white infants, South Carolina.

The birthweight distributions of Black and White infants in South Carolina were compared for the paired-year periods 1975-76 and 1985-86. No discernible changes in birthweight distributions between the two time periods were observed especially among Black infants. The distributions among White infants reflected an overall improvement in birthweight most noticeably above 2500g.     

State maternal and child expenditures and low birthweight infants: a descriptive analysis

This study examines the relationship over time between state public health spending for maternal and child health and rates of low birthweight infants. Using expenditure data from the Public Health Foundation and National Center for Health Statistics, we compare the 10 states with the highest and lowest rates of low birthweight infants in 1980 and the 10 states with the most improved and least improved low birthweight rates over a 10-year period. We hypothesize that the 10 states with the best low birthweight rates and 10 states with the most improvement in low birthweight rates will be the states with the highest levels of maternal and child health expenditures per birth. We find no support for the hypothesis in either group of states. At the state level, maternal and child public health expenditures do not appear correlated with states that are the most successful or are making the most improvement in low birthweight infants.     

Characteristics of maternal employment during pregnancy: effects on low birthweight.

BACKGROUND: Although maternal employment is considered a risk factor for low birthweight (LBW), the manner in which employment might affect birthweight is poorly understood. In this analysis, selected characteristics of employment during pregnancy were examined for effects on pregnancy outcomes. METHODS: Work characteristics included the number of hours per week, physical activities, and environmental conditions. The outcomes of interest were fetal growth retardation (less than 2500 grams at term) and preterm delivery (less than 37 weeks). The study population consisted of 2711 non-Black, married mothers who participated in the 1980 National Natality Survey (NNS). The NNS data were merged with data from the 1977 revision of The Dictionary of Occupational Titles (DOT) from which measures of occupational physical activities and environmental exposures were obtained. Logistic regression was used in the analysis. RESULTS: Those who worked 40 or more hours per week were more likely than women who worked fewer hours to have a low birthweight delivery at greater than or equal to 37 weeks. No physical or environmental characterics of work were associated with low birthweight or preterm delivery. CONCLUSIONS: Non-Black married American women may face a risk of delivering low-birthweight babies at or near term only if they work 40 or more hours each week. However, the lack of risk associated with other characteristics of work may be a function of measurement error in the DOT data source or of low levels of exposure in the analysis population.     

Association of maternal and social characteristics with age-standardised birthweight

Journal of Public Health - To identify the maternal and social characteristics associated with age standardised birthweight in a modern developed setting. Birth records (n = 414,478)...     

Similarities and disparities in maternal risk and birth outcomes of white and Japanese-American mothers

Summary. This study compares the maternal sociodemographic and prenatal care characteristics and birth outcomes of US resident white and Japanese-American mothers, using data from the state of Hawaii. The specific focus is to determine to what extent these factors can explain variations in newborn maturity and mortality indicators. Single livebirths to resident, non-military dependent white and Japanese-American mothers were selected for analysis from the 1979–1990 linked livebirth-infant death files from Hawaii. Compared with white mothers, Japanese-American mothers were significantly more likely to be married, age 18 years and older, have higher educational attainment, and have adequate prenatal care utilisation. The majority of Japanese-American mothers were born in Hawaii, while the majority of white mothers were born on the US mainland. The mean birthweight of Japanese-American infants was 200 g lighter than that of white infants. Infant mortality rates (IMRs) for both groups were below the US Year 2000 Health Objective. After controlling for maternal sociodemographic and prenatal care factors with logistic regression, Japanese-American infants had significantly higher risks of low birthweight, preterm and very preterm birth and of being small-for-gestational age. These findings indicate that populations with preferential maternal sociodemographic and prenatal care risk indicators may still exhibit higher low birthweight percentages, but achieve comparatively low IMRs.     

Energy-nitrogen balances and protein turnover in small and appropriate for gestational age low birthweight infants

The aim of the present study was to compare, under the same nursing conditions, the energy-nitrogen balance and the protein turnover in small for gestational age (SGA) and appropriate for gestational age (AGA) low birthweight infants. We compared 8 SGA's (mean +/- s.d.: gestational age 35 +/- 2 weeks, birthweight 1520 +/- 330 g) to 11 AGA premature infants (32 +/- 2 weeks, birthweight 1560 +/- 240 g). When their rate of weight gain was above 15 g/kg/d (17.6 +/- 3.0 and 18.2 +/- 2.6 g/kg/d, mean postnatal age 18 +/- 10 and 20 +/- 9 d respectively) they were studied with respect to their metabolizable energy intake, their energy expenditure, their energy and protein gain and their protein turnover. Energy balance was assessed by the difference between metabolizable energy and energy expenditure as measured by indirect calorimetry. Protein gain was calculated from the amount of retained nitrogen. Protein turnover was estimated by a stable isotope enrichment technique using repeated nasogastric administration of 15N-glycine for 72 h. Although there was no difference in their metabolizable energy intakes (110 +/- 12 versus 108 +/- 11 kcal/kg/d), SGA's had a higher rate of resting energy expenditure (64 +/- 8 versus 57 +/- 8 kcal/kg/d, P less than 0.05). Protein gain and composition of weight gain was very similar in both groups (2.0 +/- 0.4 versus 2.1 +/- 0.4 g protein/kg/d; 3.5 +/- 1.1 versus 3.3 +/- 1.4 g fat/kg/d in SGA's and AGA's respectively). However, the rate of protein synthesis was significantly lower in SGA's (7.7 +/- 1.6 g/kg/d) as compared to AGA's (9.7 +/- 2.8 g/kg/d; P less than 0.05). It is concluded that SGA's have a more efficient protein gain/protein synthesis ratio since for the same weight and protein gains, SGA's show a 20 per cent slower protein turnover. They might therefore tolerate slightly higher protein intakes. Postconceptional age seems to be an important factor in the regulation of protein turnover.     

Cigarettes, alcohol and marijuana: varying associations with birthweight

The relations of cigarette smoking, alcohol drinking and marijuana use during pregnancy to birthweight were examined in two prospectively studied pregnancy cohorts (Phases I and II). After analytic adjustment in ordinary least squares regressions for other factors that influence birthweight, cigarette smoking during at least half the pregnancy was associated with a significant decrease in mean birthweight (159 grams in Phase I, 202 grams in Phase II). In Phase II only, beer drinking was associated with a significant decrement of 8.4 grams in estimated birthweight per ounce of absolute alcohol per month. Neither wine nor liquor drinking in the Phase II data nor any of the three beverages in the Phase I data was associated with significant decrements in predicted birthweight. Furthermore, with one exception (drinking once a week in Phase II only), alcohol drinking, defined as the number of occasions per month on which any alcoholic beverage was consumed, was not associated with a change in birthweight. Regarding marijuana use, the data are not consistent between the two phases. In the Phase I data, no coherent trend in association with birthweight was observed. In the Phase II data, marijuana use 2-3 times per week, 4-6 times per week and daily was associated with increasing decrements in estimated birthweight: 127 g, 143 g and 230 g respectively. The inconsistent findings for alcohol drinking and marijuana use between phases stand in marked contrast to the consistent findings for cigarette smoking.     

The relationship between third trimester maternal weight gain,hematologic status and infant birthweight in Liberian mothers

In 1982, WHO estimated that 20 million infants had low birthweights (LBW) (i.e., <2500 g or 5.5 lb). Most were born in developing countries. Yet for Africa, few studies have examined the relationship between maternal nutrition and birth outcomes. Over 540 hospital records were examined to 1) estimate the proportion of LBW infants. Between 23 and 80 women were studied prospectively to: 2) examine the effects of maternal health complaints on pregnancy outcomes, 3) examine the relationship between weight gain during the 3rd trimester and pregnancy outcome, and 4) determine a weight gain associated with a favorable birthweight range for this sample of women. Results show a positive relationship between birthweight and 6th month maternal Hb values. A 3rd trimester gain of 6.62 kg (14.6 lb) is correlated with a favorable pregnancy outcome. Education was positively associated with 6th month pregnancy weights. Public health workers should concentrate both on iron deficiency anemia and weight gain during the last trimester to increase the chances for successful pregnancy outcomes.     

Predicting low birthweight and complicated labor in urban black women: A biopsychosocial perspective

This study explored demographic, biomedical and psychosocial factors as predictors of two adverse pregnancy outcomes: intrapartum complications and low birthweight, in 140 urban black pregnant women. The intrapartum complication rate was 18%. A four factor equation (low family functioning, advanced maternal age, working during pregnancy, and short stature) predicted intrapartum complications (80% sensitivity, 67% specificity and 35% positive predictive value). The low birthweight rate was 14%. Four factors (low family functioning, stressful events, Quetelet's Index, and cigarette smoking) predicted low birthweight (65% sensitivity, 84% specificity and 42% positive predictive value). Family functioning, alone, predicted low birthweight with 65% sensitivity, 64% specificity and 31% positive predictive value. Family functioning, was the only predictor for both outcomes. Family functioning and other psychosocial risk factors may potentially improve identification of high risk pregnant urban black women.