Gestational carriers face a significantly higher risk for severe maternal morbidity and other pregnancy complications than those conceiving naturally or via in vitro fertilization (IVF), according to a recent Canadian study.
These findings suggest that more work is needed to ensure careful selection of gestational carriers, reported lead author Maria P. Velez, MD, PhD, of McGill University, Montreal, Quebec, Canada, and colleagues.
“Although a gestational carrier should ideally be a healthy person, with a demonstrated low-risk obstetric history, it is not clear whether this occurs in practice,” the investigators wrote in Annals of Internal Medicine. “Moreover, the risk for maternal and neonatal adversity is largely unknown in this group.”
Study Compared Gestational Carriage With IVF and Unassisted Conception
To address these knowledge gaps, Dr. Velez and colleagues conducted a population-based cohort study in Ontario using linked administrative datasets. All singleton births at more than 20 weeks’ gestation with mothers aged 18-50 years were included from April 2012 to March 2021. Multifetal pregnancies were excluded, as were women with a history of infertility diagnosis without fertility treatment, and those who underwent intrauterine insemination or ovulation induction.
Outcomes were compared across three groups: Unassisted conception, IVF, and gestational carriage. The primary maternal outcome was severe maternal morbidity, defined by a validated composite of 41 unique indicators. The primary infant outcome was severe neonatal morbidity, comprising 19 unique indicators.
Secondary outcomes were hypertensive disorders, elective cesarean delivery, emergent cesarean delivery, preterm birth at less than 37 weeks, preterm birth at more than 32 weeks, and postpartum hemorrhage.
Logistic regression analysis adjusted for a range of covariates, including age, obesity, tobacco/drug dependence, chronic hypertension, and others. The final dataset included 846,124 births by unassisted conception (97.6%), 16,087 by IVF (1.8%), and 806 by gestational carriage (0.1%).
The weighted relative risk (wRR) for severe maternal morbidity was more than three times higher in gestational carriers than in those conceiving naturally (wRR, 3.30; 95% CI, 2.59-4.20) and 86% higher than in those conceiving via IVF (wRR, 1.86; 95% CI, 1.36-2.55). These stem from absolute risks of 2.3%, 4.3%, and 7.8% for unassisted, IVF, and surrogate pregnancies, respectively.
Moreover, surrogates were 75% more likely to have hypertensive disorders, 79% more likely to have preterm birth at less than 37 weeks, and almost three times as likely to have postpartum hemorrhage.
These same three secondary outcomes were also significantly more common when comparing surrogate with IVF pregnancies, albeit to a lesser degree. In contrast, surrogate pregnancies were associated with a 21% lower risk for elective cesarean delivery than IVF pregnancies (wRR, 0.79; 95% CI, 0.68-0.93).
Severe neonatal morbidity was not significantly different between the groups. These findings add to a mixed body of evidence surrounding both maternal and neonatal outcomes with gestational carriers, according to the investigators.
“Prior small studies [by Söderström-Anttila et al. and Swanson et al.] reported varying risks for preterm birth in singleton gestational carriage pregnancies, whereas a recent large US registry reported no increased risk for preterm birth compared with IVF, after accounting for multifetal pregnancy,” they wrote. “This study excluded multifetal pregnancies, a common occurrence after IVF, with reported higher risks for adverse outcomes. Accordingly, adverse maternal and newborn outcomes may have been underestimated herein.”