Mothers who smoke at the time of conception have a greater risk of carrying a smaller fetus in mid-pregnancy and delivering a lower birth weight baby.
- According to figures from the Ministry of Health from 2015, 17.8% of pregnant women are still smoking in the third trimester of their pregnancy.
- This is the highest rate in Europe, despite the health effects on pregnancy and the health of the child (increased risk of complications, intrauterine growth retardation, congenital malformations, sudden death and asthma).
Risk of miscarriage, premature birth, low birth weight, or sudden infant death syndrome… Many studies have looked into the harmful effects of tobacco consumption during pregnancy.
But, for women trying to get pregnant, smoking also poses risks. This is demonstrated by a new study published in the journal Human Reproduction. According to its authors, at the tenth week of pregnancy, the development of the embryo was delayed by almost a day in women who smoked ten or more cigarettes a day at the time of conception compared to non-smokers. The fetuses were also unable to catch up with this growth delay and were more likely to be born with a low weight.
Developmental delay that continues until birth
The researchers followed 689 women during their first pregnancy, which occurred between 2010 and 2018. They looked at the association between mothers’ smoking from 14 weeks before conception to 10 weeks after conception (known as the periconceptional period) and the development of the embryos. For this, they used the Carnegie stages, which identify the growth of the embryo during its first 10 weeks. Beyond that date, they relied on developmental information from ultrasounds and birth weight.
“The impact of periconceptional maternal smoking on delayed embryonic development appears to have a greater effect during the second trimester of pregnancy than at birth”, explains Dr. Melek Rousian, the gynecologist at the University Medical Center in Rotterdam (Netherlands) who led the study. According to her, it is possible that there will be catch-up growth during the last two trimesters of pregnancy. Nevertheless, “the delay in morphological development cannot be fully recovered during pregnancy, as shown by ultrasounds at 20 weeks and birth weights”.
For the authors of the study, these results confirm the importance of stopping smoking before conception. “If possible, women should quit smoking from the time they plan to become pregnant, but it’s always a good idea to quit anyway, especially at any stage of pregnancy. Smoking has an impact not only on the growth of the embryo during pregnancy and on its birth weight, but also on its development from the early stages of pregnancy”recalls Dr. Rousian.
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