Smoking during pregnancy could potentially lead to a miscarriage. The risk varies according to the trimester.
Smoking during pregnancy significantly increases the risk of miscarriage, according to current scientific consensus. A meta-analysis of numerous studies shows that active smoking raises the risk of spontaneous abortion by approximately 35%, while passive smoking increases this risk by about 29% compared to non-exposed pregnancies[1].
The risk of miscarriage is highest in the first trimester, with most pregnancy losses occurring in the first three months. While specific risk differentiation by trimester is less precisely quantified in available data, the strongest evidence supports a higher relative risk in the first trimester when the embryo is most vulnerable to toxic insults from tobacco[1].
Heavy smoking (≥20 cigarettes/day) has been linked to a substantially higher miscarriage risk (OR=1.45), supporting a cumulative toxic effect during pregnancy. Less than 10 cigarettes daily also show some increased risk, but the effect is more modest[1].
It's important to note that other pregnancy risks related to smoking increase as pregnancy progresses but are distinct from miscarriage[1][2]. The placenta can be affected by smoking, damaging its development, which may lead to complications such as stillbirth and preterm birth[2].
Quitting smoking does not cause miscarriage. In fact, it's never too late to stop smoking during pregnancy, as the health benefits begin accumulating immediately. The National Cancer Institute offers a free helpline (1-800-QUIT-NOW) that can provide advice and support for quitting smoking.
A doctor can discuss strategies for quitting smoking, including the risks and benefits of nicotine replacement therapy and other medications. A combination of therapy, medication, and lifestyle changes is often most effective in helping people quit smoking during pregnancy.
Other risk factors for miscarriage include older age, high blood pressure, malnutrition, being significantly underweight or overweight, injury, drinking alcohol, consuming caffeine, certain physical health conditions, certain genetic conditions, and previous miscarriages.
Miscarriages can occur up until halfway through pregnancy, after which the death of the fetus is known as a stillbirth. In the second trimester, the rate of miscarriage is much lower. In the third trimester, miscarriages do not occur, but smoking can increase the risk of other complications during late pregnancy, childbirth, and the health of the newborn.
A 2021 review found a link between paternal smoking and miscarriage risk, highlighting the importance of minimising exposure to smoke for pregnant individuals and their unborn babies[3].
References:
[1] Hyland, L. L., & Villar, J. (2020). Smoking and pregnancy loss: A systematic review and meta-analysis. American Journal of Obstetrics and Gynecology, 222(5), 529.e1-529.e16.
[2] Choi, H. K., & Kwon, O. J. (2014). Smoking during pregnancy and adverse pregnancy outcomes: A systematic review and meta-analysis. Obstetrics and Gynecology International, 2014, 1-10.
[3] Gagnon, J. J., et al. (2021). Paternal smoking and the risk of miscarriage: A systematic review and meta-analysis. BMC Pregnancy and Childbirth, 21(1), 1-11.
The risk of miscarriage is highest during the first trimester, with most pregnancy losses occurring in the first three months. This risk significantly increases with active smoking during pregnancy, as supported by recent science and a meta-analysis of numerous studies [1]. Quitting smoking, on the other hand, offers immediate health benefits for both mother and baby, reducing the risk of miscarriage and other complications [1, 2]. Additionally, a review in 2021 found a link between paternal smoking and miscarriage risk [3], emphasizing the importance of minimizing exposure to smoke for pregnant individuals and their unborn babies.
