For a study, researchers sought to assess the risks of bad birth outcomes between pregnancies conceived with and without medically assisted reproduction. From 2009 to 2017, birth certificates were used to analyze the outcomes of all neonates born in Utah. About 52.8% (N=248,013) of the 469,919 births were included in the sample, with 5.2% of the neonates conceived by medically assisted reproduction. Birth weight, gestational age, low delivery weight (LBW, less than 2,500 g), preterm birth (less than 37 weeks of gestation), and small for gestational age were all outcome measures (SGA, birth weight less than 10th percentile). For the continuous outcomes (birth weight and gestational age), linear models were calculated, while linear probability models were employed for the binary outcomes (LBW, preterm birth, SGA). First, the general sample (between-family analyses) compared the birth outcomes of neonates born following medically assisted reproduction and spontaneous conception before and after adjusting for parental background and neonatal features. Second, they used family fixed-effect models to see if neonates born by medically assisted reproduction had different birth outcomes than their natively conceived siblings (within-family comparisons).

Medically assisted reproduction-conceived neonates weighed less, were delivered sooner, and were more likely to be LBW, preterm, and SGA than neonates conceived spontaneously. More invasive treatments (assisted reproductive technology [ART] and artificial insemination [AI] or intrauterine insemination) were linked to poorer birth outcomes; for example, the proportion of LBW and preterm birth among neonates conceived naturally was 6.1% and 7.9%, respectively, compared to 25.5% and 29.8% among neonates conceived through ART. The differences in birth outcomes between neonates conceived through medically assisted reproduction and those conceived naturally were attenuated after accounting for various neonatal and parental characteristics, but they remained statistically significant; for example, neonates conceived through ART were at 3.2 percentage points higher risk for LBW (95% CI 2.4–4.1) and 4.8 percentage points higher risk for preterm birth (95% CI 3.9–5.7). For all types of treatments, the differences in unfavorable outcomes between siblings born by medically assisted reproduction and siblings born spontaneously were minor and statistically insignificant. Medically assisted reproduction procedures had been linked to poor birth outcomes. However, these concerns were unlikely to be linked to infertility treatments.