Does sex matter? Association of fetal sex and parental age with pregnancy outcomes in Taiwan: a cohort study

Worldwide several studies have examined the associations of fetal sex, paternal age and maternal age with pregnancy outcomes, with the evidence regarding paternal age being less consistent. Although in Taiwan we keep good records on birth certificates, these issues have been seldom researched. Our objective was to assess the association of fetal sex and parental age with gestational hypertension/preeclampsia, eclampsia and preterm delivery in the Taiwanese population.

We conducted a nationwide study and included 1,347,672 live births born between 2004 and 2011 in Taiwan. Gestational hypertension/preeclampsia and eclampsia were ascertained based on the International Classification of Diseases codes; preterm delivery (< 37 weeks) was defined according to the gestational age documented by healthcare providers. We implemented logistic regression models with covariates adjusted to assess the association of fetal sex and parental age with pregnancy outcomes.

The prevalence was 2.27% for gestational hypertension/preeclampsia, 0.07% for eclampsia and 6.88% for preterm delivery. After considering other parent’s age and covariates, we observed a significantly stepped increase in the risk of both gestational hypertension/preeclampsia and preterm delivery as paternal and maternal age increased. For example, fathers aged ≥50 years were associated with a significantly higher risk of gestational hypertension/preeclampsia (odds ratio [OR]: 1.60, 95% CI: 1.39, 1.84) and preterm delivery (OR: 1.38, 95% CI: 1.27, 1.51) than fathers aged 25–29 years. Analysis on fetal sex showed that relatively more female births were linked to gestational hypertension/preeclampsia and more male births linked to preterm delivery, compared to the whole population.

We found both paternal and maternal age, as well as fetal sex, were associated with the risk of pregnancy outcomes. Some findings on fetal sex contradicted with previous research using non-Asian samples, suggesting that ethnicity may play a role in the association of fetal sex and pregnancy outcomes. Besides, there is a need to counsel couples who are planning their family to be aware of the influence of both advanced maternal and paternal age on their pregnancy outcomes.