[Relations of pre-pregnant weight and weight gain during pregnancy with pregnancy-induced hypertension and birth weight].

OBJECTIVE: To determine the influence of pre-pregnant body mass index (BMI) and weight gain during pregnancy on the occurrence of pregnancy-induced hypertension (PIH) and birth weight. METHODS: Pre-pregnant BMI and pregnancy weight gain of 769 mothers giving full-term birth to a single baby for the first time were measured and the pregnancy outcomes were followed up. RESULTS: (1) The incidence of PIH and fetal macrosomia was significantly higher in the overweight group than in the normal weight and underweight groups (P<0.01 and P<0.05, respectively), but differed little between the latter two groups (P>0.05). Underweight mothers were more likely to give birth to babies with low birth weight than the normal and overweight mothers (P<0.01), but the likelihood was similar between the latter two groups (P>0.05). (2) Irrespective of the pre-pregnant BMI, PIH and fetal macrosomia occurred at higher rates with the mothers with pregnancy weight gain no less than 18 kg (P<0.01), whereas low birth weight was significantly more likely with mothers with pregnancy weight gain less than 9 kg (P<0.01). (3) A weight gain during pregnancy over 18 kg gave rise to higher risk of PIH in normal and underweight mothers, but in overweight group, PIH occurred at a significantly higher rates when a weight gain more than 9 kg was recorded (P<0.05). The incidence of fetal macrosomia was significantly higher when the maternal weight gain exceeded 18 kg in the normal weight group (P<0.01), and low birth weight occurred more frequently in relation to a maternal weight gain less than 9 kg in the normal and underweight groups (P<0.01). CONCLUSION: Pre-pregnant BMI and weight gain during pregnancy can be important factors influencing the occurrence of PIH and the neonates' birth weight.