Birth outcomes in single motherhood "by choice": A register study of children conceived through Medically Assisted Reproduction

Background Our aim was to evaluate birth outcomes among children born to single mothers through Medically Assisted Reproduction (MAR), a rapidly growing and under studied group. Methods Using Finnish population register data from 1996-2020, we compared birth weight (grams); gestational age (days); low birth weight (LBW, <2500 grams), and preterm birth (<37 weeks)) of first children born to single mothers via MAR (n=2763) to outcomes of children born to single mothers who conceived spontanesously (SC; n=45 168) and children born to partnered mothers through MAR (n=38 693) or SC (n=413 326). We compared the outcomes before and after accounting for differences in maternal socio-demographic and health characteristics (maternal age, education, income, smoking, mental health), and multiplicity. Results Children conceived by single MAR mothers had, on average, a higher prevalence of LBW (8.0%) and prematurity (10.0%), compared to children of single SC mothers (5.7% and 6.2% respectively) and children of partnered NC mothers (4.3% and 5.5% respectively). However, their birth outcomes were generally better than those of children born to partnered MAR mothers (9.7% LBW, 11.8% premature). After accounting for differences in maternal socio-demographic and health characteristics, and multiplicity in a regression, differences between birth outcomes of single MAR mothers and partnered SC mothers fully attenuated, while children born to single SC and MAR partnered mothers had worse outcomes. Conclusions Single mothers who conceive via MAR are not at increased risk of poorer birth outcomes because of the MAR treatments or the single parenthood but rather because they have high rates of multiple births. Keywords birth outcomes; low birth weight; preterm birth; Medically Assisted Reproduction; single motherhood