OBJECTIVETo research the influence of pregnancy-induced hypertension (PIH) on neonatal birth weight and its interaction with other factors.

METHODSA retrospective cohort study was conducted in this study. 14 townships were randomly selected by cluster random sampling method from 37 townships in Liuyang city, Hunan province. All pregnant women from these 14 townships with pregnancy care manual and delivery record, during April 1st, 2008 to March 31st, 2011 were selected as subjects of this study. Blood pressure during pregnancy and neonatal birth weight were recorded. Multinomial logistic regression model was used to adjust the confounding factors. Addictive effects model was used for interaction analysis.

RESULTSData from 6 102 subjects were collected, including 418 (6.9%) pregnant women with PIH, 166 (2.7%) infants with low birth weight and 333 (5.5%) with fetal macrosomia. Results from the Multinomial logistic regression analysis showed significant association between neonatal birth weight and PIH, premature birth, BMI <18.5 before pregnancy, and weight gain ≥ 16 kg during pregnancy. Data from the Interaction analysis showed that there was strong positive interactions between PIH and premature birth to low birth weight infants (RERI = 35.08, API = 0.435, S = 1.7), and between PIH and BMI<18.5 before pregnancy to low birth weight infants. However, no significant interaction was found between PIH and weight gain.

CONCLUSIONFactors as PIH, premature birth, BMI before pregnancy and weight gain showed impact on low birth weight or fetal macrosomia. PIH also showed significant interaction on neonatal birth weight with premature birth as well as BMI before pregnancy, respectively.