Objective  To examine the change in pregnancy weight gain and its associates among healthy pregnant women in Tianjin for providing evidence to precision health care during pregnancy.

  Methods  Based on the information extracted from Tianjin Municipal Information System for Maternal and Child Health Care on all 18 – 45 years old singleton pregnant women registered during 2015, 48382 healthy puerperae with full-term deliveries of infants appropriate for gestational age were enrolled in the study. The participants′ data on demographics, history of pregnancy/childbirth and familial disease, and body weight measured during prenatal examination were retrospectively collected and analyzed.

  Results   The change in the participants′ weight during the whole pregnancy showed a trend of almost no increase in first- trimester but steady increase in second- and third-trimester of pregnancy. The participants′ average median (25th percentile, 75th percentile) for weight gain during whole pregnancy was 14.15 (11.17 – 17.16) kg, and the median was 7.74 (5.63 – 9.94) kg in the first half of pregnancy and 6.38 (4.50 – 8.30) kg in the second half of pregnancy. According to the guideline of Institute of Medicine (IOM), only 38.0% or 39.2% of the participants were assessed as having appropriate weight gain based on the references of body mass index (BMI) category proposed by Chinese health authorities or World Health Organization. Assessed in the light of the guideline of IOM, the range of pregnancy weight gain for the non-obese participants was appropriate, while that for obese participants with normal delivery was slightly higher. Age, pre-pregnancy BMI, and many social and economic factors have an impact on the participants′ pregnancy weight gain.

  Conclusion  During pregnancy health care, adjusting weight management goal according to individual characteristics of pregnant women may improve the achievement rate of weight management and the health outcomes of mothers and infants.