Smoking in the weeks before and after conception has a potentially unhealthy effect on an embryo, Dutch research shows.
"Smoking not only impacts an embryo's growth during pregnancy and birth weight, but also embryo development right from the very early stages of pregnancy," said study leader Dr. Melek Rousian, a gynecologist at Erasmus University Medical Center in Rotterdam, Netherlands.
The study included nearly 700 women in the Netherlands who had single-baby pregnancies between 2010 and 2018.
By the 10th week of pregnancy, fetal development was nearly one day behind in mothers who smoked 10 or more cigarettes a day compared to nonsmokers, the study found. It was behind by 1.6 days in smokers who conceived through assisted reproduction.
Smokers' fetuses were unable to close the developmental gap, and their average birth weight was 0.2 pounds less than that of babies born to nonsmokers, the researchers said.
Their findings were published Feb. 23 in the journal Human Reproduction.
The developmental delays caused by mothers smoking soon after conception were also associated with smaller fetal measurements on ultrasound at 20 weeks' gestation, Rousian pointed out.
"We think that perhaps there is some catch-up growth during the second and third trimesters, but the delay in � development cannot be fully recuperated during the course of the pregnancy, as is shown by the 20-week ultrasound scans and birth weights," Rousian said in a journal news release.
The researchers said their findings point to the importance of not smoking before conception and that efforts to help women quit should focus on this period.
"If possible, women should stop smoking from the very moment they plan to become pregnant, but it's always a good thing to stop smoking anyway, particularly at any stage of pregnancy," Rousian said.
The March of Dimes has more about smoking and pregnancy.
SOURCE: Human Reproduction, news release, Feb. 23, 2022