Birth outcomes in single motherhood 'by choice': a register study of children conceived through medically assisted reproduction.

BACKGROUND: Single mothers 'by choice' who conceive through medically assisted reproduction (MAR) are a growing and understudied group. We examined how their infants' birth outcomes compare with other family types. METHODS: Using Finnish population register data (1996-2020), we examined five birth outcomes among first-born children: low birthweight (LBW), preterm birth, small for gestational age (SGA), gestational-age-adjusted birthweight, and gestational age. We compared children of (i) single MAR mothers (n = 2230) with those of (ii) single mothers who conceived spontaneously (SC; n = 36 352); (iii) partnered MAR mothers (n = 39 350); and (iv) partnered SC mothers (n = 451 295). Regression models adjusted for maternal age, education, income, smoking, mental health, and multiplicity. RESULTS: In unadjusted analyses, children of single MAR mothers (reference) had higher risks of LBW and preterm and lower gestational age than those of partnered and single SC mothers [e.g. odds ratio (OR) for LBW = 0.51; 95% confidence interval (CI) 0.44-0.60 and 0.69; 95% CI 0.59-0.81, respectively]. After adjustments, differences relative to the partnered SC group largely attenuated (e.g. OR for LBW = 1.01; 95% CI 0.85-1.21), whereas outcomes were better than those of single SC and partnered MAR mothers (e.g. OR for LBW = 1.21; 95% CI 1.01-1.45 and 1.30; 95% CI 1.08-1.55, respectively). The relative advantage in SGA and gestational-age-adjusted birthweight also remained after adjustment. CONCLUSIONS: After accounting for sociodemographic characteristics and multiplicity, children of single mothers 'by choice' had birth outcomes comparable to those of partnered SC mothers and more favourable than those of single SC and partnered MAR mothers.