Risk of preterm delivery in very advanced maternal age parturients utilizing in-vitro fertilization

Background: Among patients ≥45 years, the birth rate in the United States continues to increase. Fertility declines with age; this cohort often utilizes assisted reproductive technology, specifically in-vitro fertilization (IVF). While both advancing maternal age and IVF are independently associated with adverse maternal outcomes, data regarding their additive effect are scant. Objective: Determine if very advanced maternal age patients (vAMA, ≥45 years at delivery) who conceive via IVF are at increased risk for preterm birth (PTB) compared to those with non-IVF pregnancies. Study Design: Retrospective cohort study of all pregnant patients ≥45 years old who delivered at a single institution (2014- 2021). Those with incomplete delivery/neonatal records or multiples beyond twins were excluded. We compared individuals who conceived via IVF to those who conceived without IVF. The primary outcome was preterm delivery <37 weeks gestation. Secondary outcomes included other adverse perinatal outcomes. Using multivariable logistic regression, we adjusted for multiple gestation as well as confounders found to be significantly different in the univariable analysis and other known risk factors for PTB. Results: In our study cohort of 420 vAMA patients, individuals who underwent IVF were more likely to be older, privately insured, nulliparous, and with a twin gestation. The preterm birth rate in vAMA patients who underwent IVF was 24.4% compared to 8.4% in patients who did not use IVF (p< 0.001). After adjusting for confounders, IVF was an independent risk factor for preterm birth <37 weeks in vAMA patients (aOR 4.3, 95% CI 1.7-10.4, p = 0.001). In-vitro fertilization was also associated with a composite of adverse maternal outcomes (hypertensive disorder of pregnancy, postpartum hemorrhage, blood transfusion, unplanned hysterectomy) (aOR 1.7, 95% CI [1.1-2.9], p = 0.03). Conclusion: In the vAMA population, conception via IVF is associated with an increased risk of preterm birth <37 weeks.