First-Trimester Smoking Linked to Overweight Offspring

By Reuters Staff

September 08, 2020

NEW YORK (Reuters Health) - Women who quit smoking in the first trimester of pregnancy are not at increased risk of having a preterm birth or small-for-gestational-age (SGA) infant, but they are more likely to have a child who is overweight than are nonsmokers, according to new research.

"Population strategies should focus on parental smoking prevention before or at the start, rather than during, pregnancy," Dr. Elise M. Philips of Erasmus University Medical Center in Rotterdam, the Netherlands, and colleagues conclude in PLoS Medicine.

Smoking in pregnancy is a key risk factor for several birth complications, as well as childhood overweight, Dr. Philips and her team note. To investigate whether quitting early in pregnancy or smoking less would also be associated with increased risk, as well as assess the role of paternal smoking, they analyzed data from 28 pregnancy/birth cohorts including more than 229,000 singleton births from across Europe and North America.

In total, 14.4% of mothers and 27.5% of fathers reported smoking in pregnancy, and 4.7% of children were born preterm, 10% were SGA at birth and 20% were overweight.

Adverse birth outcomes were not elevated for mothers who only smoked during the first trimester, but their risk of having an overweight child increased (odds ratio, 1.17; P=0.03). Women who continued to smoke during pregnancy were at significantly increased risk of preterm birth (OR, 1.08), SGA (OR, 2.15) and childhood overweight (OR, 1.42).

Smoking fewer cigarettes between the first and third trimester was associated with reduced but nonetheless elevated risks of SGA and childhood overweight, compared with not smoking.

For women who didn't smoke during pregnancy, paternal smoking was linked to increased risks of preterm birth (OR, 1.06; P=0.05), SGA (OR, 1.04; P=0.05) and childhood overweight (OR, 1.21; P<0.001). Paternal smoking wasn't associated with preterm birth or SGA for mothers who only smoked during the first trimester, but it was linked to childhood overweight (OR, 1.36; P=0.036). Risks of each outcome were highest when both parents continued to smoke.

"Future research should investigate whether quitting smoking in the first trimester or reducing the number of cigarettes during pregnancy is also beneficial for other adverse birth and offspring outcomes," Dr. Philips and colleagues write. "Although we cannot exclude a role of residual confounding and shared family-based characteristics in the associations of paternal smoking with childhood overweight, we recommend that fathers are more closely involved in preconception and pregnancy consultations focused on smoking reduction."

SOURCE: PLoS Medicine, online August 18, 2020.