(680) The association between timing of tobacco smoking cessation and fetal growth restriction

Tobacco smoking is a leading cause of fetal growth restriction (FGR). Our objective was to estimate the association between timing of tobacco smoking cessation and FGR in a cohort of current or former smokers.

Study Design:

This retrospective cohort study includes all pregnant patients who received prenatal care and delivered in a university health system, delivered a viable neonate between 4/1/22 and 3/31/23, and reported tobacco smoking either during pregnancy or within one year prior to conception. FGR was defined as estimated fetal weight (EFW) or abdominal circumference (AC) < 10% on the most recent ultrasound prior to delivery. Bivariable and multivariable logistic regression analyses were performed. Adjusted odds ratios (aOR) are reported.

Results:

Of 343 patients included in this study (10.5% of the delivery cohort), 148 (43.2%) quit smoking in the year prior to conception or in the first trimester of pregnancy, 22 (6.1%) quit in the 2^nd trimester, 16 (4.4%) quit in the 3^rd trimester and 157 (43.6%) continued smoking. Compared to patients who quit smoking early, those who continued smoking beyond the 1^st trimester were more likely to identify as Black or Other/unknown race and to be nulliparous. After controlling for confounders, patients who quit tobacco in the year prior to pregnancy or in the first trimester were significantly less likely to be diagnosed with FGR (aOR 0.48, 95% CI 0.24 – 0.96). Smoking cessation any time prior to delivery was also associated with reduced odds of FGR (aOR 0.46, 95% CI 0.23 – 0.89) but risk reduction from quitting in the 3^rd trimester appeared attenuated.

Conclusion:

Smoking cessation pre-pregnancy or in the first trimester is associated with a 52% reduction in FGR compared to continued smoking later in pregnancy. These findings can be used to direct counseling on the benefits of tobacco cessation as early as possible.