title: Low preconception body mass index is associated with birth outcome in a prospective cohort of Chinese women.
abstract: Low maternal prepregnancy BMI is associated with adverse birth outcomes, but the BMI at which risk increases is not well defined. We assessed whether the relationship between prepregnancy BMI and birth outcomes is influenced by the extent to which mothers were underweight in a prospective study in Anhui, China. The women (n = 575) were 20-34 y old, married, nulliparous and nonsmokers. All measures of infant growth increased with increasing maternal BMI until a plateau was reached at a BMI of 22-23 kg/m2. Infants born to the 27% of women who were severely underweight before pregnancy (BMI < or = 18.5 kg/m2) were at increased risk for fetal growth deficits associated with infant morbidity. Compared with a normal BMI, being severely underweight was associated with mean (+/- SEM) reductions of 219 +/- 40 g in infant birthweight and 6.7 +/- 1.3% in the birthweight ratio and an 80% increase in risk of intrauterine growth restriction [odds ratio (OR) 1.8; 95% CI: 1.0, 3.3; P = 0.05]. Being severely underweight was also associated with smaller infant head circumference and lower ponderal index. Being moderately underweight (18.5 < BMI < 19.8 kg/m2) was not significantly associated with adverse pregnancy outcomes. Gestational age and risk of preterm birth were not associated with maternal BMI. More than half of the women in this study were underweight before pregnancy. Although being moderately underweight was not associated with increased risk of adverse pregnancy outcomes, being severely underweight was an important risk factor for reduced fetal growth.
authors: Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA. ronnenberg@comcast.net
authors: Alayne G
authors: AG
authors: Ronnenberg
authors: Xiaobin
authors: X
authors: Wang
authors: Houxun
authors: H
authors: Xing
authors: Chanzhong
authors: C
authors: Chen
authors: Dafang
authors: D
authors: Chen
authors: Wenwei
authors: W
authors: Guang
authors: Aiqun
authors: A
authors: Guang
authors: Lihua
authors: L
authors: Wang
authors: Louise
authors: L
authors: Ryan
authors: Xiping
authors: X
authors: Xu
mesh_terms: D000328:Adult; D001724:Birth Weight; D015992:Body Mass Index; D015331:Cohort Studies; D003710:Demography; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011256:Pregnancy Outcome; D012016:Reference Values; D013851:Thinness