Smoking status and maternal weight trajectories during pregnancy and postpartum: Preliminary results from a pilot study

Objective: To preliminarily examine throughout pregnancy and 12 months postpartum: 1) the critical timings of abnormal gestational weight gain (GWG) among quitters and non-quitters; 2) the consequences of abnormal GWG on weight retention during postpartum; 3) the potential difference in GWG by timing of quitting (early vs. late).

Methods: We included 59 pregnant smokers (49 quitters and 10 non-quitters) from two clinical pilot studies. Smoking status and weight were repeatedly measured throughout pregnancy and postpartum. Weight trajectories were analyzed using mixed models with smoking cessation status, pregnancy week or postpartum month, their interaction term, and potential confounders.

Results: At enrollment, mothers had a mean BMI of 28.7 (SD, 7.2) and mean age of 30.1 years (SD, 5.8). Both groups had a linear increase in GWG, but quitters had a much higher rate of GWG (0.87 vs. 0.22 pounds/week) than non-quitters throughout pregnancy. Before delivery, 63.3% of quitters and 20.0% of non-quitters had excessive total GWG, while 12.2% of quitters and 60.0% of non-quitters had inadequate total GWG (p-value=0.004). Early quitters (<21 weeks) had a higher risk of excessive GWG (85.0%) than late quitters (≥21 weeks, 36.4%) (p-value=0.026). After delivery, quitters' weight remained stable following a rapid weight loss, whereas non-quitters' weight increased continuously.

Conclusions: Non-quitters have a high risk of inadequate GWG, while quitters, especially early quitters, have a high risk of excessive GWG. The group difference in weight trajectories lasted from conception to postpartum.