Smoking only in early pregnancy still puts baby at risk

(HealthDay)—While quitting smoking during the first trimester slightly decreases the risk for low birth weight in newborns, any duration of maternal smoking during pregnancy is associated with low birth weight and abnormal body proportions, according to a study recently published in BMJ Open.

Isabel Rumrich, from the University of Eastern Finland in Kuopio, and colleagues examined the effects of maternal first-trimester smoking cessation versus continued smoking on newborn body size and body proportions. Participants included singleton newborns without congenital anomalies born between 1991 and 2016 to a cohort of mothers from the Finnish Medical Birth Register.

The researchers found that of the 1,376,778 births included in the study, 84.5 percent of mothers were nonsmokers, 3.5 percent quit smoking during the first trimester, and 12 percent continued smoking after the first trimester. Babies born to mothers who continued smoking after the first trimester had an increased risk for high ponderal index, low brain-to-body ratio, and high head-to-length ratio (22, 10, and 19 percent absolute risks, respectively). These risks were slightly lower for babies born to mothers who quit smoking during the first trimester.

"The most important finding of our study is that although quitting smoking in the first trimester reduces the risk of low birth weight, brain size and body length in relation to body weight seem not to catch up," Rumrich said in a statement. "This stresses the importance of quitting smoking already before pregnancy, since even smoking only during early pregnancy can have devastating effects on the long-term health of the unborn child."