Infertility, infertility treatment, and mixed-handedness in children

Abstract

Background Mixed-handedness, which may reflect atypical brain laterality, has been linked to a number of medical conditions as well as prenatal stress. Aims The aim of the study was to examine whether infertility or infertility treatment was associated with an increased risk of mixed-handedness in children. Study design, subjects and outcome measures We used data from three population-based birth cohorts in Denmark: the Aalborg-Odense Birth Cohort (1984–1987), the Aarhus Birth Cohort (1990–1992) and the Danish National Birth Cohort (1996–2002) ( N = 7728, 5720 and 29486, respectively). Data on time to pregnancy and infertility treatment were collected during pregnancy. Handedness was reported in a follow-up questionnaire when the children were at least 7 years old. Children were categorized as mixed-handed if their mothers reported that they used both hands equally. Results Children born after infertility treatment, particularly intrauterine insemination, had a higher risk of being mixed-handed compared to children of fertile couples with a time to pregnancy ≤ 12 months (odds ratio 1.41, 95% confidence interval 1.09–1.82). Children of couples with unplanned pregnancies, particularly after an oral contraceptives failure, were also more likely to be mixed-handed. There was no association between a long waiting time to pregnancy and mixed-handedness in children. Conclusions Children born after infertility treatment, particularly intrauterine insemination, and children exposed to oral contraceptives during early gestation may have a higher risk of being mixed-handed.