Comment: The quality of evidence is upgraded by consistent findings and dose-response effect.
A systematic review and meta-analysis 1 included 54 studies (n=30 245 946) reporting obstetrical and neonatal outcomes in pregnancies where gestational weight gain was below instead of within (the IOM and ACOG) guidelines per class of maternal obesity. There were significantly less large for gestational age neonates (LGA), preeclampsia, and caeserean deliveries in the group with gestational weight gain less than the recommended guidelines (tableT1), no heterogeneity, P<00001, except for preeclampsia class III P=0.006). Signifant reductions were also seen with postpartum weight gain and composite neonatal morbidity.
In unvariate studies (11 515 411 pregnancies), in pregnancies with lower than recommended weight gain higher odds were seen for small for gestational age neonate (SGA) among those with obesity class I and II (OR 1.30; 95% CI 1.17 to 1.45, and OR 1.56, 95% CI 1.31 to 1.85, respectively), but not in class III. However, the incidence of SGA was below the expected limits (<10%) and was not associated with increased neonatal morbidity. Furthermore, after adjusting for covariates (18 730 535 pregnancies), that difference was not statistically significant anymore.
No significant differences were seen in gestational diabetes mellitus between groups. Regarding preterm birth, univariate analysis studies only reported on overall obesity and mixed iatrogenic and spontaneous preterm birth showing a significant increase, whereas the adjusted multivariate studies showed no significant differences.
| Outcome | Odds ratio (95% confidence interval) | ||
|---|---|---|---|
| BMI 30-34.9 kg/m2 (class I) | BMI 35-39.9 kg/m2 (class II) | BMI > 40 kg/m2 (class III) | |
| Large for gestational age | OR 0.69 (0.64 to 0.73) | OR 0.68 (CI 0.63 to 0.74) | OR 0.65 (0.57 to 0.75) |
| Preeclampsia | OR 0.71 (0.63 to 0.79) | OR 0.82 (0.73 to 0.91) | OR 0.82 (0.70 to 0.94) |
| Caesarean delivery | OR 0.76 (0.72 to 0.81) | OR 0.82 (0.77 to 0.87) | OR 0.87 (0.82 to 0.91) |
| Postpartum weight retention | 0.20 (0.05 to 0.82) in the overall obesity group (P=0.03) | ||
| Composite neonatal morbidity | 0.93 (0.87 to 0.99) in the overall obesity group (P=0.04) | ||
A retrospective cohort study 6 included 30 910 pregnant women. 7569 pregnancy women had less than recommended GWG, 13 088 had adequate GWG, and 10 253 had excessive GWG. The incidence of macrosomia and LGA continues to increase from inadequate GWG to excessive GWG groups (dose-response). Pregnant women without GDM who have excessive GWG were at higher risk of macrosomia (a-OR 2.19; 95% CI 1.83 to 2.63) and LGA (a-OR 2.19, 95% CI 1.89 to 2.54) than pregnant women with GDM. Moreover, this risk increased with increasing pre-pregnancy BMI. Only those with inadequate GWG and pre-pregnancy BMI < 18.5 kg/m2 had an increased risk of SGA.
Date of latest search: 2023-03-02
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