Introduction: The impact of gestational weight loss (GWL) on fetal growth in women with obesity remains controversial. Our study aims to examine the respective associations of GWL (net weight loss from pre-pregnancy to delivery) with small for gestational age (SGA < 10th percentile) and large for gestational age (LGA > 90th percentile) neonates among women with obesity.
Methods: We conducted a population-based retrospective cohort study of women with obesity (pre-pregnancy body mass index ≥30kg/m2) who had a singleton birth between 2012 and 2017 in Ontario. Adjusted risk ratios (aRRs) and 95% confidence intervals (CIs) for the association between GWL and fetal growth were estimated by using multivariate regression models. Interaction effects were examined to determine whether the impact of GWL on fetal growth varied by obesity classes (I: 30-34.9kg/m2, II: 35-39.9kg/m2 and III: 40kg/m2 or higher).
Results: Among 89,835 eligible women, 5,276 (5.9%) women with obesity experienced GWL during pregnancy. Overall, GWL in women with obesity had an increased risk of SGA (aRR: 1.43, 95% CI[1.24-1.64]) and a decreased risk of LGA (aRR: 0.84, 95% CI[0.74-0.94]), compared to the recommended gestational weight gain (5-9kg) group. There were significant interaction effects between GWL and obesity classes on SGA (Wald p<0.01) and LGA (Wald p<0.01) neonates. GWL in women with obesity was significantly associated with increased risk of SGA neonates for all obesity classes with aRRs of 1.33, 95% CI[1.08-1.62] for class I, 1.49, 95% CI[1.14-1.95] for class II, and 1.89, 95% CI[1.37-2.60] for class III. Comparatively, the aRRs (95% CIs) of LGA were 1.03 (0.83-1.28), 0.81 (0.65-1.02), and 0.69 (0.56-0.84) for class I, II, and III obesity, respectively.
Conclusion: Our study demonstrated GWL in women with obesity was significantly associated with increased risk of SGA neonates. GWL should not be recommended in women with obesity.
Yanfang Guo– Adjunct Professor and Epidemiologist, School of Epidemiology and Public Health, University of Ottawa Faculty of Medicine, ON, CA
Katherine Muldoon– Research Associate, OMNI Research Group, Clinical Epidemiology Program, Ottawa Hospital Research Institute
Daniel Corsi– Adjunct Professor, School of Epidemiology and Public Health, University of Ottawa Faculty of Medicine, Ottawa, Canada
Ruth Rennicks White– Research Program & Operations Manager, OMNI Research Group, Department of Obstetrics, Gynecology, and Newborn Care, University of Ottawa Faculty of Medicine, Ottawa, Canada
Alysha Harvey– Manager, Ottawa Hospital Research Institute
Shi Wu Wen– Professor and Senior Scientist, School of Epidemiology and Public Health, University of Ottawa Faculty of Medicine, Ottawa, Canada
Darine El-Chaâr– Physician, Department of Obstetrics, Gynecology & Newborn Care, The Ottawa Hospital, Ottawa, Canada
Laura Gaudet– Doctor of Medicine, Maternal Fetal Medicine. Associate Scientist and Professor., Queen's University