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Smoking before or following conception causes the embryo to suffer a certain delay in its development. A study published in
«Human Reproduction» ensures that the fact that the mothers smoke during the period immediately before and following conception not only causes such a delay in embryonic development, but that the fetuses are smaller at the time of the 20-week ultrasound and there is a greater risk of low birth weight.
The research has monitored 689 women with singleton pregnancies between 2010 and 2018 and has seen that, in the tenth week of pregnancy, the development of the embryo was delayed by almost a day in women who smoked ten or
more cigarettes per day compared to non-smokers, and by 1.6 days in smokers who had conceived through in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).
In addition, researchers led by Melek Rousian of the
Erasmus University Medical Center in Rotterdam (Netherlands) found that the delay was not recoverable. That is, the embryos might not ‘catch up’ their development during pregnancy and were more likely to be born smaller for gestational age and with an average birth weight of 93 grams lower than those born to non-smoking mothers.
“One of the key messages from this study is that delayed embryonic development due to tobacco use in the periconceptional period is also associated with a smaller fetus at 20-week ultrasound and lower birth weight,” he says. Melek Roussian.
This is the first study to investigate the association between maternal smoking mothers from 14 weeks before from conception to 10 weeks following conception, which is called the periconceptional period, and the development of the embryos.
The term periconcepcional is an important area of research because many expectant parents are unaware of the presence of a developing embryo in the early days when a pregnancy has not yet been confirmed.
The researchers used virtual reality to observe the development of the embryos and compared the morphology with established stages of embryo development, known as the Carnegie stages.
Because the Carnegie stages only cover embryonic development during the first 10 weeks of gestation, researchers were unable to compare embryo shapes to an agreed standard beyond this stage, but ultrasound scans and birth weight provided information on development, including arm circumferences. the head and abdomen and length of the thigh bone.
“The impact of periconceptional maternal smoking on delayed embryonic development appears to have a greater effect in the second trimester of pregnancy than at birth,” Rousian explains. We think there may be catch-up growth during the second and third trimesters, but the morphological developmental delay may not be fully recovered during pregnancy, as shown by 20-week ultrasounds and birth weights.”
The results, he notes, “emphasize the importance of quitting before conception and that efforts to help women quit smoking should be focused on this window of time. If possible, women should stop smoking from the moment they plan to become pregnant, but it’s always good to quit anyway, especially at any stage of pregnancy. Smoking not only affects the growth of an embryo during pregnancy and birth weight, but also the development of the embryo from the early stages of pregnancy.”
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