[Effect of pre-pregnancy weight and gestational weight gain on neonatal birth weight:a prospective cohort study in Chongqing City].

OBJECTIVE

To explore the effect of pre-pregnancy weight and gestational weight gain in Chongqing City on birth weight of newborns.

METHODS

Pregnant women were volunteered for the cohort study in 6 Maternal and Child Centers in Chongqing from January 2016 to June 2017, who were planning to be pregnant in latest 3 months. The basic information included height and weight of prepregnancy, first trimester, mid-trimester and third trimester of pregnancy, and pregnancy outcome were collected. ANOVA, chi square test and multi factor unconditional logistic regression model were used to analyze the data.

RESULTS

In pre-pregnancy the major BMI of women were <18. 5(46. 74%, 1119/2394) and 18. 5≤BMI≤29. 99(47. 12%, 1128/2394), in first trimester of pregnancy, the figures were <18. 5(34. 46%, 825/2394) and 18. 5≤BMI≤29. 99(57. 77%, 1383/2394). The distribution BMI in above stages were statistically different(χ2=74. 95, P<0. 01). The incidence of the low birth weight and macrosomia were 4. 51%(108/2394) and 6. 89%(165/2394). The average of neonatal birth weight, the low birth weight and macrosomia were statistically different(F=24. 18, P<0. 01) and(χ2=66. 44, P<0. 01) comparisons among all prepregnancy BMI groups. The average birth weight of newborns, the low birth weight of the newborn and macrosomia were statistically different(F=11. 27, P<0. 01), and(χ~2=89. 53, P<0. 01) comparisons among all IOM groups of three stages of pregnancy. Low weight in pregnancy is the risk factor for low birth weight infants(RR=1. 90(95%CI 1. 27-2. 86)), while excessive gestational weight gain is the protective factor(RR=0. 66(95%CI 0. 46-0. 96)). Prepregnancy obesity(RR=3. 06(95%CI 1. 77-5. 31)) and excessive weight gain during pregnancy(RR=3. 60(95%CI 2. 48-5. 22)) were the risk factors for macrosomia. The above two factors, prepregnancy obesity and excessive weight gain during pregnancy interacted multiply.

CONCLUSION

The figures of pre-pregnancy BMI are not equal to the BMI in first trimester of pregnancy. Low weight in pre-pregnancy is the risk factor for low birth weight infants, while excessive weight gain during pregnancy is the protective factor. Prepregnancy obesity and excessive weight gain during pregnancy are the risk factors for macrosomia. Prepregnancy obesity and excessive weight gain during pregnancy interacted multiply.