Risk of severe maternal morbidity by maternal fertility status: a US study in 8 states

Over the past 2 decades the characteristics of women giving birth in the United States and the nature of the births themselves have changed dramatically, with increases in older maternal age, plural births, cesarean deliveries, and conception from infertility treatment.

We sought to evaluate the risk of severe maternal morbidity by maternal fertility status, and for in vitro fertilization pregnancies, by oocyte source and embryo state combinations.

Women in 8 states who underwent in vitro fertilization cycles resulting in a live birth during 2004 through 2013 were linked to their infant's birth certificates; a 10:1 sample of births from non-in vitro fertilization deliveries were selected for comparison; those with an indication of infertility treatment on the birth certificate were categorized as subfertile, all others were categorized as fertile. In vitro fertilization pregnancies were additionally categorized by oocyte source (autologous vs donor) and embryo state (fresh vs thawed). Maternal morbidity was identified from the birth certificate, modeled using logistic regression, and reported as adjusted odds ratios [95% confidence intervals]. The reference group was fertile women.

The study population included 1,477,522 pregnancies (1,346,118 fertile, 11,298 subfertile, 80,254 in vitro fertilization autologous-fresh, 21,964 in vitro fertilization autologous-thawed, 13,218 in vitro fertilization donor-fresh, and 4670 in vitro fertilization donor-thawed pregnancies): 1,420,529 singleton, 54,573 twin, and 2420 triplet+ pregnancies. Compared to fertile women, subfertile and the 4 groups of in vitro fertilization-treated women had increased risks for blood transfusion and third- or fourth-degree perineal laceration (subfertile, 1.58 [1.23-2.02] and 2.08 [1.79-2.43]; autologous-fresh, 1.33 [1.14-1.54] and 1.37 [1.26-1.49]; autologous-thawed, 1.94 [1.60-2.36] and 2.10 [1.84-2.40]; donor-fresh, 2.16 [1.69-2.75] and 2.11 [1.66-2.69]; and donor-thawed, 2.01 [1.38-2.92] and 1.28 [0.79-2.08]). Also compared to fertile women, the risk of unplanned hysterectomy was increased for in vitro fertilization-treated women in the autologous-thawed group (2.80 [1.96-4.00]), donor-fresh group (2.14 [1.33-3.44]), and the donor-thawed group (2.46 [1.33-4.54]). The risk of ruptured uterus was increased for in vitro fertilization-treated women in the autologous-fresh group (1.62 [1.14-2.29]). Among women with a prior birth, the risk of blood transfusion after a vaginal birth was increased for subfertile women (2.91 [1.38-6.15]), and women in all 4 in vitro fertilization groups (autologous-fresh, 1.93 [1.23-3.01]; autologous-thawed, 2.99 [1.78-5.02]; donor-fresh, 5.13 [2.39-11.02]; and donor-thawed, 5.20 [1.83-14.82]); the risk after a cesarean delivery was increased in the autologous-thawed group (1.74 [1.29-2.33]) and the donor-fresh group (1.62 [1.07-2.45]). Unplanned hysterectomy was increased in the autologous-thawed (2.31 [1.43-3.71]) and donor-thawed (2.45 [1.06-5.67]) groups.

The risks of severe maternal morbidity are increased for subfertile and in vitro fertilization births, particularly in pregnancies that are not from autologous, fresh cycles.