Association of Mandatory COVID-19 Lockdown Exposure with Increased Maternal Prenatal Smoking and Reduced Fetal Head Growth: A Retrospective Cohort Study.

OBJECTIVES: Maternal psychological distress during COVID-19 has been linked to reduced neonatal brain volume. This study aimed to determine whether mandatory COVID-19 lockdown exposure was associated with reduced fetal head growth and to identify maternal, behavioral, and obstetric factors associated with this relationship. METHODS: A retrospective cohort study compared pregnancies during mandatory COVID-19 lockdown (March-December 2020) with the corresponding 2019 period. Women with SARS-CoV-2 infection, multiple gestations, and congenital anomalies or infections were excluded. The primary outcome was third-trimester fetal head circumference (HC) z-score. Covariates included maternal demographic, obstetric, and clinical factors, including prenatal smoking (consistent reporting at every prenatal visit). Linear mixed-effects models with interaction terms were used. RESULTS: A total of 1,116 pregnancies (545 exposed, 571 unexposed) were included. Lockdown exposure was associated with greater weight gain (11 vs. 10 kg, p < 0.01), higher prenatal smoking (6.1% vs. 1.2%, p < 0.01), more hypertensive disorders (7.2% vs. 4.4%, p = 0.04), and longer gestation (39.1 vs. 39.0 weeks, p < 0.01), plus lower third-trimester fetal HC z-scores (0.7 vs. 0.9, p < 0.01). The interaction between lockdown exposure and prenatal smoking was independently associated with reduced fetal HC (β = -1.6; 95% CI, -2.7 to -0.4; P = 0.03); smoking alone was not significant (β = -5.2; P = 0.24). CONCLUSIONS FOR PRACTICE: Mandatory COVID-19 lockdown exposure was associated with reduced fetal head growth, in interaction with increased prenatal smoking, highlighting the need for targeted smoking-cessation support during public health emergencies.