Determinant of Low Birth Weight Infants: A Matched Case Control Study

To estimate the effect of low-dose aspirin started in early pregnancy on the incidence of preeclampsia and intrauterine growth restriction (IUGR). A systematic review and meta-analysis were performed through electronic database searches (PubMed, Cochrane, Embase). Randomized controlled trials of pregnant women at risk of preeclampsia who were assigned to receive aspirin or placebo (or no treatment) were reviewed. Secondary outcomes included IUGR, severe preeclampsia and preterm birth. The effect of aspirin was analyzed as a function of gestational age at initiation of the intervention (16 weeks of gestation or less, 16 weeks of gestation or more). Thirty-four randomized controlled trials met the inclusion criteria, including 27 studies (11,348 women) with follow-up for the outcome of preeclampsia. Low-dose aspirin started at 16 weeks or earlier was associated with a significant reduction in preeclampsia (relative risk [RR] 0.47, 95% confidence interval [CI] 0.34-0.65, prevalence in 9.3% treated compared with 21.3% control) and IUGR (RR 0.44, 95% CI 0.30-0.65, 7% treated compared with 16.3% control), whereas aspirin started after 16 weeks was not (preeclampsia: RR 0.81, 95% CI 0.63-1.03, prevalence in 7.3% treated compared with 8.1% control; IUGR: RR 0.98, 95% CI 0.87-1.10, 10.3% treated compared with 10.5% control). Low-dose aspirin started at 16 weeks or earlier also was associated with a reduction in severe preeclampsia (RR 0.09, 95% CI 0.02-0.37, 0.7% treated compared with 15.0% control), gestational hypertension (RR 0.62, 95% CI 0.45-0.84, 16.7% treated compared with 29.7% control), and preterm birth (RR 0.22, 95% CI 0.10-0.49, 3.5% treated compared with 16.9% control). Of note, all studies for which aspirin had been started at 16 weeks or earlier included women identified to be at moderate or high risk for preeclampsia. Low-dose aspirin initiated in early pregnancy is an efficient method of reducing the incidence of preeclampsia and IUGR.

Objective To determine the relation between overweight and obesity in mothers and preterm birth and low birth weight in singleton pregnancies in developed and developing countries. Design Systematic review and meta-analyses. Data sources Medline and Embase from their inceptions, and reference lists of identified articles. Study selection Studies including a reference group of women with normal body mass index that assessed the effect of overweight and obesity on two primary outcomes: preterm birth (before 37 weeks) and low birth weight (<2500 g). Data extraction Two assessors independently reviewed titles, abstracts, and full articles, extracted data using a piloted data collection form, and assessed quality. Data synthesis 84 studies (64 cohort and 20 case-control) were included, totalling 1 095 834 women. Although the overall risk of preterm birth was similar in overweight and obese women and women of normal weight, the risk of induced preterm birth was increased in overweight and obese women (relative risk 1.30, 95% confidence interval 1.23 to 1.37). Although overall the risk of having an infant of low birth weight was decreased in overweight and obese women (0.84, 0.75 to 0.95), the decrease was greater in developing countries than in developed countries (0.58, 0.47 to 0.71 v 0.90, 0.79 to 1.01). After accounting for publication bias, the apparent protective effect of overweight and obesity on low birth weight disappeared with the addition of imputed “missing” studies (0.95, 0.85 to 1.07), whereas the risk of preterm birth appeared significantly higher in overweight and obese women (1.24, 1.13 to 1.37). Conclusions Overweight and obese women have increased risks of preterm birth and induced preterm birth and, after accounting for publication bias, appeared to have increased risks of preterm birth overall. The beneficial effects of maternal overweight and obesity on low birth weight were greater in developing countries and disappeared after accounting for publication bias.