Bengü Mutlu Sütcüoğlu, Cemre Karçaaltıncaba, Deniz Karçaaltıncaba
Eurasian Journal of Medical Investigation - 2026;10(1):65-72
Objectives: Maternal smoking during pregnancy impairs fetal growth, yet the relative contribution of trimester-specific exposure and cessation timing remains unclear. Quantitative trimester-based analyses that integrate cigarette dose and neonatal outcomes are limited. Methods: This retrospective, population-based study used data from the CDC WONDER Natality database (United States, 2016-2024). Women who reported smoking at the beginning of pregnancy and had complete trimester-specific data were included. Smoking exposure was analyzed both categorically and quantitatively (cigarettes per day). The primary outcome was neonatal birth weight (grams); a secondary analysis assessed small-for-gestational-age (SGA) among term deliveries. Multivariable linear regression was adjusted for maternal age, pre-pregnancy BMI, gestational weight gain, interpregnancy interval, and pregnancy-related morbidities. ROC analysis identified discriminatory thresholds. Results: Among 4,931 pregnancies, second-trimester smoking showed the strongest independent negative association with birth weight (B=-1.246 g per cigarette; p<0.001), followed by first-trimester smoking (B=-0.957 g; p<0.001). Third-trimester smoking had minimal clinical impact. Second-trimester cessation was associated with higher birth weight (p<0.001), whereas third-trimester cessation showed no benefit. Among term births, only first-trimester smoking was associated with SGA (p=0.022). A threshold of 15 cigarettes per day predicted SGA with a sensitivity of 71% and a specificity of 75%. Conclusion: Smoking timing critically determines fetal growth impact, underscoring the importance of very early cessation.
