Smoking influence on early and late fetal growth

Area of Science:

• Obstetrics and Gynecology
• Perinatal Medicine
• Maternal-Fetal Medicine

Background:

• Smoking during pregnancy is a significant, modifiable risk factor for adverse fetal outcomes.
• Fetal growth restriction (FGR) and low birthweight are leading causes of neonatal morbidity and mortality.
• Understanding the impact of maternal smoking on fetal development across gestation is crucial.

Purpose of the Study:

• To investigate the association between maternal smoking and the development of early (<34 weeks) and late (>34 weeks) fetal growth restriction (FGR) or low birthweight.
• To examine the effects of smoking on uteroplacental and fetoplacental hemodynamics in growth-restricted fetuses.

Main Methods:

• Retrospective cohort study of 5,537 singleton pregnancies.
• Pregnancies categorized into early (<34 weeks) and late (>34 weeks) delivery groups.
• FGR diagnosed using customized fetal growth standards and fetal Doppler; birthweight assessed with the Olsen newborn chart.

Main Results:

• In late deliveries (>34 weeks), smoking was significantly associated with FGR (5% vs 1.3%, p<0.001) and lower birthweights (<3rd and <10th centiles).
• Late FGR in smokers showed higher umbilical artery Doppler resistances.
• No significant association between smoking and FGR, birthweight, or hemodynamics was found in early deliveries (<34 weeks).

Conclusions:

• Maternal smoking is associated with increased risk of FGR, low birthweight, and altered fetal hemodynamics after 34 weeks gestation.
• The detrimental effects of smoking on fetal growth appear more pronounced in later stages of pregnancy.
• Interventions to reduce smoking during pregnancy may be particularly impactful for preventing late-onset FGR.