Impact of Maternal Smoking on Obstetric and Neonatal Outcomes in Twin Pregnancies: A Narrative Review.

Maternal smoking, including both traditional cigarettes and electronic ones, is a significant modifiable risk factor associated with adverse perinatal outcomes, especially in twin pregnancies. This narrative review aims to explore the impact of maternal smoking on obstetric and neonatal outcomes in twin pregnancies, which inherently carry a higher risk of complications. A literature search was conducted using the PubMed and EMBASE databases, selecting studies published between January 1994 and October 2024. The findings demonstrate a clear association between smoking and increased risks of preterm birth and fetal growth restriction (FGR) in twin pregnancies. These risks are exacerbated when smoking is combined with other factors, such as preeclampsia and elevated body mass index (BMI). Smoking was also associated with long-term post-natal complications, including respiratory problems like asthma, as well as cognitive and behavioral disorders. However, an association with preeclampsia was not found, and further studies are needed to clarify the relationship in the fields of preterm premature rupture of membranes (PPROM) and fetal death. The adverse effects of smoking are primarily due to reduced oxygen supply to the fetus, caused by nicotine-induced vasoconstriction and carbon monoxide exposure, leading to placental insufficiency and fetal hypoxia. These effects are amplified in twin pregnancies due to the increased physiological demands. The review highlights that smoking cessation interventions during pregnancy are crucial to mitigate these risks and improve maternal and neonatal health outcomes.