Medically assisted reproduction and the risk of preterm birth: a case-control study using data from the Quebec...

The use of fertility treatments has been growing over the past decade, but these treatments are not without risk. We aimed to quantify the risk of preterm birth associated with the use of ovarian stimulators (OS) and assisted reproductive technologies (ART) overall and by type of fertility treatment.

We conducted a case-control analysis of data from the Quebec Pregnancy Cohort. We included singleton pregnancies ending in a live birth during the time when Quebec operated a universal reimbursement program for assisted reproduction (2010-2015). Fertility treatments were defined dichotomously, and pregnancies resulting from spontaneous conception were used as the reference. We categorized fertility treatments into subgroups: ovarian stimulators alone, ART alone and OS and ART combined. Preterm birth was defined as birth before 37 weeks' gestation. We estimated odds ratios (ORs) for the association between type of assisted reproduction and preterm birth using generalized estimating equation models and adjusted ORs for potential confounders.

A total of 57 624 pregnancies were included in the study. During the study period, 2055 pregnancies were conceived through the use of OS, ART or both: 419 involved OS alone, 150 involved ART alone and 1486 involved both OS and ART. When we adjusted for potential confounders, conception with OS, ART or both was associated with an increased risk of preterm birth (adjusted OR 1.46, 95% confidence interval [CI] 1.25-1.72, 182 exposed cases). All types of assisted reproduction were associated with an increased risk of preterm birth compared with pregnancies conceived spontaneously (OS alone: adjusted OR 1.47, 95% CI 1.04-2.07; ART alone: adjusted OR 1.76, 95% CI 1.01-3.06; OS and ART combined: adjusted OR 1.43, 95% CI 1.19-1.73). Use of OS or ART or both was associated with an increased risk of late, moderate and extremely preterm birth (extremely preterm birth: adjusted OR 2.39, 95% CI 1.30-4.39).

Compared with pregnancies conceived spontaneously, pregnancies conceived through the use of OS, ART or both were associated with a 46% increased risk of preterm birth. Physicians should advise patients of the increased risks of late, moderate and extremely preterm birth so that they can make informed choices.