Response to Pre-Pregnancy Blood Pressure and Offspring Sex in the HUNT Study, Norway

We thank Haug et al. for their interest in our recent findings on maternal blood pressure prior to pregnancy and subsequent sex of the baby at delivery.^1,2 As previously reported,¹ in 1,411 women participating in a prospective preconception cohort study in China, we noted that maternal systolic blood pressure measured at median 26.3 weeks prior to pregnancy was higher in those who went on to deliver a boy, as compared to those who delivered a girl (both before and after covariate adjustment). Furthermore, on logistic regression analyses, maternal pregravid systolic blood pressure emerged as the only significant predictor of subsequently delivering a male baby.¹ As this association certainly requires confirmation in other populations, we read with interest the letter by Haug et al. describing a comparable analysis in 2,427 women from Norway.² They found no significant difference in blood pressure at median 3 years before pregnancy in those who delivered a boy as compared to those who delivered a girl. The question thus arises of how to reconcile these conflicting findings.

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