Biological risk versus socio-economic advantage: low birth-weight, multiple births and income variations among Irish infants born following fertility treatments.

The Growing Up in Ireland Infant Cohort dataset (n = 11,134) includes information on fertility treatments for over 400 infants. IVF (28.1 %) and IVF-related treatments (17.8 %) were the most frequent, but there was also a high percentage following clomiphene citrate alone (31.5 %). Infants born following fertility treatment were much more likely to be in higher income families, and this relationship was not accounted for by older mothers in wealthier families. Analysis of fertility-treatment pregnancies among Irish infants, controlling for income and maternal age, shows a greater risk of multiple birth and low birth-weight, although the latter appears to be largely related to the former especially for IVF-type treatments.