Basic characteristics of the research population
Among the 722 patients enrolled in the study, 83.5% primiparas and 16.5% multiparas were analyzed. The study population had an average maternal age of 31.7 ± 6.1 years at enrollment, a mean gestational period of 38.7 ± 1.7 weeks, and an average pre-pregnancy BMI of 23.6 ± 1.7 kg/m2. In addition, the entire population had a mean GWG of 13.10 ± 4.88 kg, whereas those of underweight, normal weight, overweight and obese individuals were 14.6 ± 4.1, 13.8 ± 4.4, 12.0 ± 5.5 and 9.6±5.5 kg, respectively. Analysis of pregnancy outcomes revealed that 22.6, 12.3, 5.4, and 10.9% of the study subjects had developed GDM, gestational hypertension, preeclampsia and PPH, respectively. With regards to modes of delivery, 56.8,8.3 and 34.9% of the women required vaginal, assisted vaginal and cesarean section delivery, respectively. Furthermore, 8.7, 1.8 and 18.8% of the newborns were characterized with macrosomia, SGA and LGA, respectively.
The relationship between pre-pregnancy BMI and pregnancy outcomes
Among the 722 subjects, 6.5, 63.7, 21.1 and 8.7 % were underweight, normal weight, overweight, and obese, respectively, prior to pregnancy. Underweight women experienced a higher possibility of SGA birth (OR 12.35, 95% CI 3.56-42.82) and vaginal delivery (OR 2.21, 95% CI 1.09-4.50), compared to women with normal weight before pregnancy. Conversely, underweight was negatively correlated with the risk of LGA (OR 0.21, 95% CI 0.05-0.88) (Table 2). Moreover, overweight and obese PCOS women had a higher risk of developing gestational hypertension (OR 4.86, 95% CI 2.82-8.39; and OR 6.05, 95% CI 2.97-12.33, respectively), undergoing cesarean section (OR 1.71, 95% CI 1.15-2.55; and OR 2.10, 95% CI 1.18-3.74, respectively), and having an infant with LGA (OR 2.57, 95% CI 1.64-4.04; and OR 2.22, 95% CI 1.12-4.39, respectively) when compared with normal weight women. On the other hand, overweight women were more likely to develop preeclampsia (OR 4.08, 95% CI 1.95-8.51) and result in macrosomia at birth (OR 2.15, 95% CI 1.14-4.05).
The association between GWG and adverse pregnancy outcomes
According to the IOM guidelines, approximately 23% of women in this study experienced inadequate weight gain, whereas 45 and 32% of them gained the recommended and more than recommended weight, respectively. With regards to the effect of GWG on pregnancy complications (Table 3), 4.1, 13, and 17.4% of women in the inadequate, adequate and excessive GWG groups, respectively, had gestational hypertension, whereas 4.7, 11.8 and 14.3% of those achieved inadequate, adequate and excessive GWG, respectively, developed PPH. Significantly lower (P<0.05) incidences of gestational hypertension and PPH were recorded in the inadequate GWG groups, whereas significantly higher (P<0.001) LGA and macrosomia incidences were recorded in the excessive GWG relative to the other 2 groups. Results from multivariate logistic regression for assessing the relationship between GWG categories with pregnancy outcomes are outlined in Table 4. Specifically, individuals in the inadequate GWG group had a lower risk of developing gestational hypertension(OR 0.28, 95%CI 0.12-0.66)and PPH(OR 0.38, 95%CI 0.17-0.84), compared to those in the adequate GWG group. On the other hand, those in the excessive GWG group were more likely to deliver macrosomia(OR 1.93, 95%CI 1.05-3.54)and give birth to LGA infants (OR 1.94, 95%CI 1.27-2.96). Subgroup analyses, based on stratification of body mass indices, revealed that inadequate GWG decreased the risks of gestational hypertension(OR 0.24, 95%CI 0.08-0.71) and PPH(OR 0.38, 95%CI 0.16-0.95)in women with BMI <25 kg/m2 before pregnancy(Table 5). Moreover, excessive GWG was significantly related to the higher possibility of LGA birth(OR 2.41, 95%CI 1.40-4.18)in women with BMI <25kg/m2 as well as chances of undergoing a cesarean section(OR 2.06, 95%CI 1.01-4.20)in women with BMI ≥25kg/m2 (Table 6).
Table 1
Recommendations for total weight gain during pregnancy, by pregnancy body mass index, according to the guidelines of the Institute of Medicine and National Research Council (2009).
Pre-pregnancy Weight category
|
Body Mass Index (kg/m2)
|
Recommended Range of Total Weight (kg)
|
Underweight
|
<18.5
|
12.5–18.0
|
Normal Weight
|
18.5–24.9
|
11.5–16.0
|
Overweight
|
25.0-29.9
|
7.0-11.5
|
Obese
|
≥ 30
|
5.0–9.0
|
Table 2
The relationship among BMI categories and maternal/fetal outcomes
Outcome
|
Underweight
Adjusted OR
(95% CI)
|
Normal Weight
Adjusted OR
(95% CI)
|
Overweight
Adjusted OR
(95% CI)
|
Obesity
Adjusted OR
(95% CI)
|
Gestational
hypertension
|
0.24[0.03–1.80]
|
1
|
4.86[2.82–8.39]**
|
6.05[2.97–12.33]**
|
Preeclampsia
|
0.55[0.07–4.29]
|
1
|
4.08[1.95–8.51]**
|
1.46[0.40–5.37]
|
Gestational diabetes
|
0.56[0.21–1.51]
|
1
|
1.33[0.85–2.09]
|
1.23[0.65–2.32]
|
Postpartum
hemorrhage
|
0.18[0.02–1.35]
|
1
|
1.60[0.91–2.81]
|
1.88[0.83–4.24]
|
Cesarean section
|
0.55[0.25–1.20]
|
1
|
1.71[1.15–2.55]*
|
2.10[1.18–3.74]*
|
Assisted vaginal
delivery
|
0.36[0.08–1.56]
|
1
|
0.50[0.23–1.12]
|
0.41[0.12–1.42]
|
Vaginal delivery
|
2.21[1.09–4.50]*
|
1
|
0.75[0.51–1.09]
|
0.65[0.37–1.14]
|
Macrosomia
|
0.46[0.10–2.07]
|
1
|
2.15[1.14–4.05]*
|
1.54[0.52–4.55]
|
SGA
|
12.35[3.56–42.82]**
|
1
|
0.41[0.05–3.62]
|
NS
|
LGA
|
0.21[0.05–0.88]*
|
1
|
2.57[1.64–4.04]**
|
2.22[1.12–4.39]*
|
OR = odds ratio; CI = confidence interval; SGA = small for gestational age; LGA = large for gestational age; NS = the number in this category was too small to analyze; |
Data was analyzed using multivariable logistic regression analysis. Models were adjusted for maternal age, height, gravidity, parity, gestational age at delivery, weight gain during pregnancy, cigarette smoke pre-pregnancy and alcohol consumption pre-pregnancy.
Reference group: normal weight for pre-pregnancy
* p < 0.05; ** p < 0.001;
Table 3
The relationship between maternal/fetal outcomes and GWG
Outcome
|
Inadequate GWG
(N = 169)
|
Adequate GWG
(N = 323)
|
Excessive GWG (N = 230)
|
p-Value
|
Gestational
hypertension (N)
|
7(4.1%)
|
42(13%)
|
40(17.4%)
|
<0.001
|
Preeclampsia (N)
|
5(3%)
|
17(5.3%)
|
17(7.4%)
|
0.15
|
Gestational diabetes
|
64(37.9%)
|
69(21.4%)
|
30(13%)
|
<0.001
|
Postpartum
hemorrhage (N)
|
8(4.7%)
|
38(11.8%)
|
33(14.3%)
|
0.008
|
Cesarean section (N)
|
56(33.1%)
|
108(33.4%)
|
88(38.3%)
|
0.43
|
Assisted vaginal
delivery (N)
|
14(8.3%)
|
30(9.3%)
|
16(7.0%)
|
0.62
|
Vaginal delivery (N)
|
99(58.6%)
|
185(57.3%)
|
126(54.8%)
|
0.73
|
Macrosomia (N)
|
7(4.1%)
|
22(6.8%)
|
34(14.8%)
|
<0.001
|
SGA (N)
|
4(2.4%)
|
5(1.5%)
|
4(1.7%)
|
0.72
|
LGA (N)
|
18(10.7%)
|
53(16.4%)
|
72(31.3%)
|
<0.001
|
SGA = small for gestational age; LGA = large for gestational age; N = number of cases. |
Table 4
The relationship between GWG categories and pregnancy outcomes
Outcome
|
Inadequate GWG
Adjusted OR p-Value
(95% CI)
|
Excessive GWG
Adjusted OR p-Value
(95% CI)
|
Gestational
hypertension
|
0.28[0.12–0.66] 0.003
|
1.15[0.69–1.91] 0.59
|
Preeclampsia
|
0.56[0.20–1.56] 0.26
|
1.36[0.66–2.78] 0.41
|
Gestational
diabetes
|
2.30[1.49–3.54] <0.001
|
0.49[0.30–0.80] 0.004
|
Postpartum
hemorrhage
|
0.38[0.17–0.84] 0.02
|
1.21[0.73–2.04] 0.46
|
Cesarean section
|
0.88[0.58–1.34] 0.56
|
1.28[0.88–1.87] 0.19
|
Assisted vaginal
delivery
|
0.97[0.49–1.92] 0.93
|
0.64[0.34–1.24] 0.19
|
Vaginal delivery
|
1.13[0.76–1.67] 0.55
|
0.91[0.64–1.29] 0.58
|
Macrosomia
|
0.67[0.27–1.66] 0.39
|
1.93[1.05–3.54] 0.03
|
SGA
|
1.23[0.31–4.87] 0.77
|
1.25[0.32–4.95] 0.75
|
LGA
|
0.65[0.36–1.17] 0.15
|
1.94[1.27–2.96] 0.002
|
OR = odds ratio; CI = confidence interval; SGA = small for gestational age; LGA = large for gestational age |
Data was analyzed using multivariable logistic regression analysis. Models were adjusted for maternal age, height, gravidity, parity, gestational age at delivery, pre-pregnancy BMI, as well as pre-pregnancy cigarette smoke and alcohol consumption.
Reference group: adequate GWG group
Table 5
Pregnancy outcomes among women whose weight gain was below levels recommended by guidelines of the Institute of Medicine
|
BMI<25 kg/m2
|
BMI ≥ 25 kg/m2
|
Outcome
|
Adjusted OR
(95% CI)
|
p-Value
|
Adjusted OR
(95% CI)
|
p-Value
|
Gestational
hypertension
|
0.24[0.08–0.71]
|
0.01
|
0.27[0.05–1.33]
|
0.11
|
Preeclampsia
|
0.62[0.19–2.01]
|
0.42
|
NS
|
|
Gestational
diabetes
|
2.55[1.54–4.23]
|
<0.001
|
2.16[0.87–5.38]
|
0.10
|
Postpartum
hemorrhage
|
0.38[0.16–0.95]
|
0.04
|
0.22[0.02–1.95]
|
0.17
|
Cesarean section
|
0.83[0.52–1.33]
|
0.43
|
0.94[0.38–2.34]
|
0.89
|
Assisted vaginal
delivery
|
0.88[0.42–1.84]
|
0.73
|
1.18[0.14–10.02]
|
0.88
|
Vaginal delivery
|
1.23[0.79–1.92]
|
0.35
|
1.06[0.43–2.63]
|
0.90
|
Macrosomia
|
0.78[0.28–2.14]
|
0.63
|
0.26[0.02–3.37]
|
0.30
|
SGA
|
1.43[0.36–5.67]
|
0.61
|
NS
|
|
LGA
|
0.54[0.25–1.16]
|
0.11
|
1.05[0.34–3.23]
|
0.93
|
OR = odds ratio; CI = confidence interval; SGA = small for gestational age; LGA = large for gestational age; NS = the number in this category was too small to analyze; |
Data was analyzed using multivariable logistic regression analysis. Models were adjusted for maternal age, height, gravidity, parity, gestational age at delivery, cigarette smoke pre-pregnancy and alcohol consumption pre-pregnancy.
Reference group: adequate GWG in the same BMI category
Table 6
Pregnancy outcomes among women whose weight gain was above recommended levels
|
BMI <25 kg/m2
|
BMI ≥ 25 kg/m2
|
Outcome
|
Adjusted OR
(95% CI)
|
p-Value
|
Adjusted OR
(95% CI)
|
p-Value
|
Gestational
hypertension
|
0.43[0.17–1.11]
|
0.08
|
1.85[0.86-4.00]
|
0.12
|
Preeclampsia
|
0.48[0.13–1.79]
|
0.27
|
2.08[0.69–6.32]
|
0.20
|
Gestational
diabetes
|
0.31[0.14–0.72]
|
0.006
|
0.56[0.27–1.17]
|
0.12
|
Postpartum
hemorrhage
|
1.15[0.57–2.30]
|
0.70
|
1.50[0.70–3.21]
|
0.29
|
Cesarean section
|
0.94[0.57–1.54]
|
0.80
|
2.06[1.01–4.20]
|
0.048
|
Assisted vaginal
delivery
|
0.88[0.42–1.83]
|
0.72
|
0.43[0.07–2.74]
|
0.37
|
Vaginal delivery
|
1.10[0.70–1.73]
|
0.69
|
0.56[0.28–1.12]
|
0.10
|
Macrosomia
|
1.90[0.87–4.17]
|
0.11
|
2.17[0.69–6.79]
|
0.19
|
SGA
|
1.29[0.28–5.82]
|
0.74
|
NS
|
|
LGA
|
2.41[1.40–4.18]
|
0.002
|
1.53[0.73–3.23]
|
0.26
|
OR = odds ratio; CI = confidence interval; SGA = small for gestational age; LGA = large for gestational age; NS = the number in this category was too small to analyze; |
Data was analyzed using multivariable logistic regression analysis. Models were adjusted for maternal age, height, gravidity, parity, gestational age at delivery, cigarette smoke pre-pregnancy and alcohol consumption pre-pregnancy.
Reference group: adequate GWG in the same BMI category