Higher maternal parathyroid hormone concentration at delivery is not associated with smaller newborn size

Abstract

Intrauterine growth restriction (IUGR) reflects inadequate growth in-utero and is prevalent in low resource settings. This study aimed to assess the association of maternal delivery parathyroid hormone (PTH) – a regulator of bone turnover and calcium homeostasis – with newborn anthropometry, to identify regulators of PTH, and to delineate pathways by which maternal PTH regulates birth size using path analysis. This was a cross-sectional analysis of data from participants (n = 537) enrolled in the Maternal Vitamin D for Infant Growth trial in Dhaka, Bangladesh. Primary exposures were maternal delivery intact PTH (iPTH) or whole PTH (wPTH) and outcomes were gestational age- and sex-sta ndardized z-scores for birth length (LAZ), weight (WAZ), and head circumference (HCAZ). Hypothesized regulators of PTH included calcium and protein intake, vitamin D, magnesiu m, fibroblast-like growth factor-23 (FGF23), and C-reactive protein. Maternal iPTH was no t associated with birth size in linear regression analyses; however, in path analysis models, every SD increase in log(iPTH) was associated with 0.08SD (95% CI: 0.002, 0.162) higher LAZ. In linear regression and path analysis models, wPTH was positively associated with W AZ. Vitamin D suppressed PTH, while FGF23 was positively associated with PTH. In path an alysis models, higher magnesium was negatively associated with LAZ; FGF23 was positiv ely associated and protein intake was negatively associated with LAZ, WAZ, and HCAZ. Higher maternal PTH in late pregnancy is unlikely to contribute to IUGR. Future studie s should investigate maternal FGF23, magnesium and protein intake as regulators of fetal grow th, particularly in settings where food insecurity and IUGR are public health problems.

Keywords

• parathyroid hormone
• pregnancy
• fetal growth
• intrauterine growth restriction
• vitamin d
• 25-hydroxyvitamin d
• fgf23
• small-for-gestational age