Smoking, 17 Alpha-Hydroxyprogesterone Caproate, and Preterm Birth.

Area of Science:

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

Background:

• Preterm birth (PTB) remains a leading cause of neonatal morbidity and mortality.
• 17 alpha-hydroxyprogesterone caproate (17OHP-C) is a treatment used to reduce the risk of recurrent PTB.
• The influence of maternal smoking on the efficacy of 17OHP-C has not been fully elucidated.

Purpose of the Study:

• To investigate whether maternal smoking status modifies the effectiveness of 17OHP-C in preventing preterm birth.
• To compare the efficacy of 17OHP-C in pregnant individuals who smoke versus those who do not.

Main Methods:

• Secondary analysis of data from the Maternal-Fetal Medicine Units Network trial of 17OHP-C.
• Comparison of preterm birth prevalence by smoking status and treatment group using chi-squared analysis.
• Analysis of variance (ANOVA) to compare gestational age at birth.
• Multivariable modeling to assess the interaction between smoking and 17OHP-C treatment.

Main Results:

• Maternal smoking significantly modified the effectiveness of 17OHP-C.
• In smokers, 17OHP-C significantly reduced PTB before 37 and 35 weeks, and spontaneous PTB before 37 and 35 weeks.
• In nonsmokers, 17OHP-C only reduced PTB before 37 weeks.
• Delivery gestational age was significantly later in smokers treated with 17OHP-C compared to placebo (36.4 vs. 34.3 weeks).
• Multivariable models indicated 17OHP-C was more effective in smokers for multiple PTB outcomes.

Conclusions:

• Maternal smoking status significantly modifies the effectiveness of 17OHP-C treatment in women with a history of preterm birth.
• The findings suggest that 17OHP-C may offer greater benefits in reducing preterm birth for women who smoke.