Abstract
OBJECTIVE
To systematically investigate a wide range of obstetrical and neonatal outcomes with respect to gestational weight gain (GWG) below the current IOM and ACOG guidelines compared to within the guidelines and to stratify outcomes by the class of obesity and by the type of study analysis.
DATA SOURCES
We systematically searched studies on PubMed, Scopus, Embase, and Cochrane Library from 2009 to April 30, 2021.
STUDY ELIGIBILITY CRITERIA
Studies reporting on obstetrical and neonatal outcomes of singleton pregnancies with respect to GWG below the current IOM and ACOG guidelines compared to within the guidelines, investigated in obesity overall (BMI> 30 kg/m2), and/or class of obesity (I: BMI 30-34.9 kg/m2, II: BMI 35-39.9 kg/ m2 and III: BMI> 40 kg/m2).
METHODS
Among the studies that met criteria, multiple obstetrical and neonatal outcomes were tabulated and compared between pregnancies with weight gain below the guidelines and those with weight gain within the guidelines, further classified by the class of obesity if applicable. Primary outcomes included small for gestational age (SGA), large for gestational age (LGA), preeclampsia (PE), and gestational diabetes mellitus (GDM). Secondary outcomes included cesarean section (CS), preterm birth (PTB), postpartum weight retention, and composite neonatal morbidity. Meta-analysis of univariate and adjusted multivariate analysis studies were conducted. The random-effect model was used to pool the mean differences or odds ratios (OR) and the corresponding 95% confidence intervals (CIs). Heterogeneity was assessed using the I2 value. Newcastle Ottawa Scale (NOS) was used to assess individual study quality.
RESULTS
Total of 54 studies reporting on 30,245,946 pregnancies were included, of which 11,515,411 pregnancies were in the univariate analysis and 18,730,535 pregnancies in the adjusted multivariate analysis. In the meta-analysis of univariate studies, compared to women who gained within the guidelines, those who gained below the guidelines had higher odds for SGA in obesity class I and II (OR:1.30 (95% CI 1.17, 1.45), I2 0%, P<0.00001, and OR: 1.56 (95% CI 1.31, 1.85), I2 0%, P<0.00001), respectively), however, the incidence of SGA was below the expected limits (<10%) and was not associated with increased neonatal morbidity. Furthermore, after adjusting for covariates, that difference was no statistically significant anymore. The difference was not statistically significant for class III obesity. Following adjusted multivariate analysis, no significant differences in SGA rates were noted for all classes of obesity between groups. Significantly lower odds for LGA were seen in GWG below guidelines in obesity class I, II, and III (OR: 0.69 (95% CI 0.64, 0.73), I2 0%, P<0.00001, OR: 0.68 (95% CI 0.63, 0.74), I2 0%, P<0.00001, and OR: 0.65 (95% CI 0.57, 0.75), I2 34%, P<0.00001, respectively), and similar findings were seen in the adjusted multivariate analysis. Women with weight gain below guidelines had significantly lower odds for PE in obesity class I, II, and III (OR: 0.71 (95% CI 0.63, 0.79),), I2 0%, P<0.00001, OR: 0.82 (95% CI 0.73, 0.91), I2 0%, P<0.00001, and OR: 0.82 (95% CI 0.70, 0.94), I2 0%, P=0.006, respectively), and similar findings were seen in the adjusted multivariate analysis. No significant differences were seen in GDM between groups. Regarding PTB, available univariate analysis studies only reported on overall obesity and mixed iatrogenic and spontaneous PTB showing significant increase in the odds of PTB (OR: 1.42 (95% CI 1.40, 1.43), I2 0%, P<0.00001) in women with low weight gain, while adjusted multivariate studies in overall obesity and in all three classes and showed no significant differences of PTB between groups. Women with low weight gain had significantly lower odds for CS in obesity class I, II, and III (OR: 0.76 (95% CI 0.72, 0.81), I2 0%, P<0.00001, OR: 0.82 (95% CI 0.77, 0.87), I2 0%, P<0.00001, and OR: 0.87 (95% CI 0.82, 0.91), I2 0%, P<0.00001, respectively), and similar findings were seen in the adjusted multivariate analysis. There was significantly lower odds for postpartum weight retention (OR: 0.20 (95% CI 0.05, 0.82)), I2 0%, P=0.03) and lower odds for composite neonatal morbidity in the overall obesity group with low GWG (OR: 0.93 (95% CI 0.87, 0.99)), I2 19.6%, P=0.04).
CONCLUSION
Contrary to previous reports, the current systematic review and meta-analysis showed no significant increase in SGA rates in pregnancies with weight gain below the current guidelines for all classes of maternal obesity. Furthermore, gaining below the guidelines was associated with lower LGA, PE, and CS rates. Our study provides the evidence that the current recommended GWG is high for all classes of obesity. These results provide pertinent information supporting the notion to revisit the current GWG recommendations for women with obesity and furthermore to classify them by the class of obesity rather than one overall obesity category as is done in the current recommendations.
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