| Objective:1 To observe the effects of pre-pregnancy BMI and gestational weight gain on birth weight and incidence of macrosomia.2 To explore the range of adequate gestational weight gain by pre-pregnancy BMI.3 To compare the pregnancy outcomes in groups with different pre-pregnancy BMI or gestational weight gain.Method:Randomly selected women who delivered a singleton, full-term infant at Shijiazhuang Obstetrics and Gynecology Hospital from October to December in 2014. Women who suffered from premature birth, post-term birth, multiple births, stillborn fetus, serious hypertension, gestational hypertension, cardiac disease and gestational diabetes were not included. SPSS 13.0 was used for data analysis. Both single factor and multiple factors analysis were used.Results:1 A total of 2175 women fulfilled our inclusion criteria, the mean of maternal age was 28.3±3.8 years old, 55.9% of them were in the range of 25-29 years; the average gestational age was 39.2±1.0 weeks; the mean of pre-pregnancy BMI was 21.4±2.9kg/m2, pre-pregnancy underweight, normal overweight and obesity was 16.4%, 66.0%, 14.9%, 2.7% respectively; the average weight gain during pregnancy was 16.7±5.0kg, 61.0% of them ranged from 9 to 18kg; the average birth weight was 3388.8±410.0g, the low-birth weight, normal birth weight and fetal macrosomia was 0.9%, 91.4%, 7.6% respectively.2 One-way ANOVA results: The birth weight was significantly different in distinct maternal age, gestational week, frequency of pregnancy, weight gain during pregnancy, pre-pregnancy BMI, anemia and sex of infant(P<0.05). There was no significant differences between birth weight and domicile, occupation, pregnancy complicated with hypothyroidism or subclinical hypothyroidism(P>0.05). Multiple linear regression analysis results: The results showed a significant positive correlation between birth weight and BMI at pre-pregnancy and weight gain during pregnancy(P<0.05), after correcting factors including age, gestational week, frequency of pregnancy, domicile, occupation, anemia, pregnancy complicated with hypothyroidism, subclinical hypothyroidism and sex of infant. The standardized partial regression coefficients were lower than the gestational age.3 Univariate logistic regression: The six variables, including maternal age, gestational age, frequency of pregnancy, weight gain during pregnancy, BMI at pre-pregnancy, sex of infant, showed strong difference with the incidence of macrosomia(P<0.05); The other factors including domicile, occupation, anemia, pregnancy complicated with hypothyroidism and subclinical hypothyroidism showed no difference with the incidence of macrosomia(P>0.05). Multivariate logistic regression: The five variables, including gestational age, parity, sex of infant, showed difference with the incidence of macrosomia(P<0.05) which was higher in the pregnant women with a long gestational age, the second or the third child and a boy. After controlling the three factors above, pre-pregnancy overweight/obesity increased the risk of being macrosomia(OR, 1.77; 95%CI, 1.18-2.65; and OR, 1.29; 95%CI, 0.44-3.75) and women with high gestational weight gain were also at high risk(OR, 2.02; 95%CI, 1.44-2.85).4 The composition of the weight gain in groups with different BMI was distinct(P<0.05) and more than 55.0 percent of the women gained 9.0-18.0kg during pregnancy. 22.8 percent of the obesity gained less than 9.0kg and that was highest in those four groups. Only 8.8 percent gained more than 18.0kg and that was the lower than any other group.5 The AUC by combined weight gain during pregnancy and BMI at pre-pregnancy to predict incidence of macrosomia was 0.667(95%CI, 0.626-0.707). The AUC to predict incidence of macrosomia with maternal age, gestational week, frequency of pregnancy, weight gain during pregnancy, BMI at pre-pregnancy, sex of infant, domicile, anemia, pregnancy complicated with hypothyroidism and subclinical hypothyroidism was 0.717(95%CI, 0.680-0.755). There was no significant difference between two AUC(P>0.05). The equation between weight gain during pregnancy(X1) and BMI at pre-pregnancy(X2) was: 0.085X1+0.135X2≤4.28.6 The rates of anemia in the late pregnancy were 52.3%, 44.0%, 44.2% and 36.8% respectively in pre-pregnancy underweight, normal weight, overweight and obesity while the women who were underweight before pregnancy were vulnerable to anemia(P<0.05).The rates of anemia in the late pregnancy accounted for 38.9%, 44.5% and 47.2% respectively in women who gained less than 9.0kg, 9.0-18.0kg or more than 18.0kg and there was no significant difference in the three groups.7 The incidences of the hypothyroidism or subclinical hypothyroidism induced by pregnancy were 6.5%, 6.3%, 5.3%, 3.5% respectively among underweight, normal weight, overweight and obesity and there was no statistically significant difference in the incidences(P>0.05).The incidences of the hypothyroidism or subclinical hypothyroidism in women who gained less than 9.0kg, 9.0-18.0kg or more than 18.0kg were 4.4%, 6.9% and 4.8% and there was no significant difference in the incidence(P>0.05).8 The rates of cesarean section were 17.1%, 23.6%, 39.5% and 50.9% respectively among women who were underweight, normal weight, overweight and obesity. The rates of cesarean section in women with underweight, overweight and obesity were 0.67 times(OR, 0.67; 95%CI, 0.49-0.91), 2.12 times(OR, 2.12; 95%CI, 1.64-2.73) and 3.36 times(OR, 3.36; 95%CI, 1.97-5.73) more than those with normal weight in the univariate logistic regression analysis. But in the multivariate logistic regression analysis, there was no significant difference in the rates of cesarean section between the underweight and normal weight women and the rates of cesarean section in women with overweight and obesity were 1.82 times(OR, 1.82; 95%CI, 1.37-2.42) and 3.71 times(OR, 3.71; 95%CI, 2.03-6.79) more than those with normal weight.The rates of cesarean section were 17.1%, 23.6%, 39.5% and 50.9% respectively among women who gained less than 9.0kg, 9.0-18.0kg or more than 18.0kg. There was no significant difference in the rates of cesarean section between the women who gained less than 9.0kg and 9.0-18.0kg but the rate in the women who gained more than 18.0kg was 1.23 times(OR, 1.23; 95%CI, 1.00-1.51) more than the women gained 9.0kg-18.0kg based on the univariate logistic regression analysis. But in the multivariate logistic regression analysis, the rate in the women who gained more than 18.0kg was 1.51 times(OR, 1.51; 95%CI, 1.20-1.89) more than the women gained 9.0kg-18.0kg.9 The incidences of premature rupture of membranes(PROM) were 16.6%, 19.2%, 14.4% and 15.8% respectively among women who were underweight, normal weight, overweight and obesity. The rate of PROM in women with overweight was less than those with normal weight(OR, 0.71; 95%CI, 0.51-1.00) and there was no significant difference in the rates between the underweight, obesity and the normal weight in the univariate logistic regression analysis(P>0.05). But in the multivariate logistic regression analysis, there was no significant difference in the rates of PROM among the three groups.There was no significant difference in the rates of PROM among the women who gained less than 9.0kg, 9.0-18.0kg or more than 18.0kg whether in the univariate logistic regression analysis or the multivariate logistic regression analysis(P>0.05).10 No significant difference was found in the total labor course among underweight, normal weight, overweight and obesity which was 9.32±3.68 h, 9.01±4.00 h, 8.85±4.17 h and 8.21±3.91h(P>0.05). The total labor course of women who gained less than 9.0kg, 9.0-18.0kg or more than 18.0kg was 8.44±4.26 h, 8.83±3.93 h, 9.48±3.95 h and there was significant difference in any two groups(P<0.05). But in the multiple linear regression analysis, there was no significant difference in women with distinct BMI or weight gain(P>0.05).11 The bleeding amount after delivery in two hours during normal labor was 297.9±42.6ml, 300.5±50.7ml, 302.9±44.3ml, 300.4±23.8ml respectively among women who were underweight, normal weight, overweight and obesity and there was no difference in those three groups(P>0.05).The amount of blood loss during cesarean section was 331.0±107.0ml, 330.8±88.4ml, 335.2±103.9ml, 358.6±133.5ml among women who were underweight, normal weight, overweight and obesity and there was no significant difference in the four groups(P>0.05).The bleeding amount after delivery in two hours during normal labor was 294.8±20.5ml, 301.2±48.2ml, 300.1±49.3ml respectively among women who gained less than 9.0kg, 9.0-18.0kg or more than 18.0kg and there was no difference in those three groups(P>0.05).The amount of blood loss during cesarean section was 325.9±57.7ml、340.4±105.9ml、323.7±85.9ml among women who gained less than 9.0kg, 9.0-18.0kg or more than 18.0kg and there was no difference in those three groups(P>0.05).12 The average systolic pressure was 116.1±10.2mm Hg, 117.7±10.3mm Hg, 119.2±10.3mm Hg, and 119.6±9.0mm Hg respectively among women who were underweight, normal weight, overweight and obesity and the average diastolic pressure was 74.2±7.3mm Hg, 75.0±7.9mm Hg, 76.6±7.5mm Hg and 77.6±7.7mm Hg.There was significant difference in the four groups(P<0.01). No matter the systolic pressure or the diastolic pressure in the underweight was lower than that in overweight and obese(P<0.05) and the diastolic pressure in the obesity was also higher than that in normal weight(P<0.05).The average systolic pressure was 115.3±9.8mm Hg, 117.1±10.4mm Hg, and 119.1±9.9mm Hg respectively among women who gained less than 9.0kg, 9.0-18.0kg or more than 18.0kg and the average diastolic pressure was 73.9±8.1mm Hg, 75.0±7.8mm Hg and 75.7±7.6mm Hg. There was significant difference in the four groups(P<0.05). The systolic pressure in the women who gained less than 9.0kg and 9.0-18.0kg was lower than that in women who gained more than 18.0kg(P<0.05) and the diastolic pressure in the women who gained less than 9.0kg was lower than that in women gained more than 18.0kg(P<0.05).In the multiple linear regression, the results showed a significant positive correlation between blood pressure and BMI at pre-pregnancy or weight gain during pregnancy(P<0.001)Conclusions:1 The infant birth weight is affected by multiple factors, the effect of gestational week may be stronger than weight gain during pregnancy and BMI at pre-pregnancy;2 The weight gain during pregnancy is positive correlated with infant birth weight, over weight gain can lead to the increased incidence of macrosomia;3 The BMI at pre-pregnancy is positive correlated with the birth weight of infants and women with over body weight at pre-pregnancy may be a high risk of macrosomia;4 The recommendation about weight gain during pregnancy for Chinese people is needed for clinical practice;5 The management of body weight before and during pregnancy can reduce the rate of cesarean section;6 The women who were overweight and obesity before pregnancy and gained much weight often have a higher blood pressure than that of others. |
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