Search

Objective: To examine the impact of changes in birth weight distribution in individual groups and in birth weight-specific fetal death rates on the decline in the crude fetal death rate in the United States., Methods: Data on live births and fetal deaths in the U.S. for the period 1979-1990 were examined by birth weight group and race using Kitagawa's method for analysis of the crude fetal death rate., Results: In the period 1979-1990, all racial groups had a decrease in the crude fetal death rate, more so in whites and others (about 22%) than in blacks (10%). In the white population, 73.4% of the total reduction in the crude fetal death rate was attributable to the improvement in birth weight-specific fetal death rates, and the remaining portion of the reduction was due to a favorable change in birth weight distribution. In the black population, the reduction in the crude fetal death rate was entirely attributable to the improvement in the birth weight-specific fetal death rates. However, in other groups, a favorable change in the birth weight distribution was the major determinant. Although black births represented 16.5% of all births in the U.S., they accounted for 26-29% of the crude fetal death rate. Disparity in the crude fetal death rates for blacks and whites is explained almost entirely by differences in birth weight distribution., Conclusions: A further decrease in the crude fetal death rate in the U.S. requires a decrease in low birth weights, particularly in blacks.

We sought to determine by what amount the frequency of low birth weight (LBW) could be reduced by eliminating its known, preventable risk factors. Based on the prevalence of risk factors such as cigarette smoking (exposure) in a population, and the degree of association (relative risk) between the risk factors and the outcome of LBW, we estimated the percentage of LBW in the United States attributable to the risk factors (population-attributable risk percentage). We found the following associations with known preventable LBW: Cigarette smoking accounts for 9.6%; alcohol consumption during pregnancy, 2.3%; low pre-pregnancy weight (less than 54 kg), 6.3%; urinary tract infections, 1.3%; Chlamydia trachomatis genital infections, 4.8%; and narcotics addiction, 3.8%. Because these risk factors are not mutually exclusive, eg, narcotics addicts may be addicted to both narcotics and cigarettes, the maximum preventable population-attributable risk percentage for LBW is less than the sum of the individual risk factors, which is 28.1% (9.6% [cigarette smoking] + 2.3% [alcohol consumption] + 6.3% [low pre-pregnancy weight] + 1.3% [urinary tract infection] + 4.8% [Chlamydia] + 3.8% [narcotics addiction] = 28.1%). Given the current state of knowledge about preventable risk factors, LBW can be reduced--in an idealized model--from only 6.9 to 5.0% of all births. In a more realistic model, we estimate that LBW can be reduced from only 6.9 to 6.3% of all births. Therefore, a national effort is indicated to identify unknown preventable causes of LBW.

The effect of mode of delivery on the mortality and morbidity of 26- to 32-week neonates was studied. Five hundred six consecutive deliveries at 26 to 32 weeks' gestation were reviewed. The populations were divided into high-risk and low-risk neonates by evaluation of antepartum variables known to increase neonatal risk, ie, abruptio placenta. One hundred ninety-six infants were classified as low risk. In this group, 124 vaginal and 72 cesarean section deliveries were compared using demographic, peripartum, and neonatal variables. Cesarean delivery was associated with highly significant maternal morbidity, including a 30% incidence of vertical uterine incision. No difference in neonatal mortality was shown. Cesarean delivery was associated with lower one-minute Apgar scores and a greater incidence and severity of hyaline membrane disease. No neonatal differences were shown in the incidence of trauma, intraventricular hemorrhage, or seizures. This study does not support cesarean delivery of all tiny neonates.

Factors affecting the survival of 136 consecutive live-born infants delivered at 24 to 28 weeks' gestation during a 4-year period were analyzed. After careful assessment of gestational age, perinatal care for the fetus of at least 26 weeks' gestation was aggressive. Survival at 26 weeks was 45% and at 28 weeks, 92%. Multivariate analysis showed that the set of variables that best predicts neonatal outcome is gestational age, antepartum glucocorticoid administration, and resuscitation at birth.