Exploring the concept of functional vitamin D deficiency in pregnancy: impact of the interaction between 25-hydroxyvitamin D and parathyroid hormone on perinatal outcomes

• Published in: The American journal of clinical nutrition Vol. 108; no. 4; pp. 821 - 829
• Main Authors: Hemmingway, Andrea, Kenny, Louise C, Malvisi, Lucio, Kiely, Mairead E
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.10.2018; Oxford University Press; American Society for Clinical Nutrition, Inc
• Subjects: 25-Hydroxyvitamin D; Adult; Blood Pressure; Calcium; Calcium - metabolism; Calcium, Dietary - metabolism; Cohort Studies; Female; Gestation; gestational hypertension; Humans; Hypertension; Infant, Newborn; Infant, Small for Gestational Age - blood; Ireland - epidemiology; mean arterial pressure; Nutrient deficiency; Nutritional Status; Parathyroid; Parathyroid hormone; Parathyroid Hormone - blood; Parity; perinatal; Pre-eclampsia; Pre-Eclampsia - blood; Pre-Eclampsia - epidemiology; Pregnancy; Pregnancy complications; Pregnancy Complications - blood; Pregnancy Complications - epidemiology; Pregnancy Complications - physiopathology; Pregnancy Outcome; Prevalence; Prospective Studies; Regression analysis; Regression models; Risk; Small for gestational age; Vitamin C; Vitamin D; Vitamin D - analogs & derivatives; Vitamin D - blood; Vitamin D Deficiency - blood; Vitamin D Deficiency - complications; Vitamin D Deficiency - epidemiology; Vitamin deficiency; Ireland; parathyroid hormone; PR; 25-hydroxyvitamin D; PTH; SCOPE; vitamin D; pregnancy; mean arterial pressure; pre-eclampsia; SGA; BP; gestational hypertension; small-for-gestational-age; perinatal; 25(OH)D; 25(OH)D2; 25(OH)D3; MAP
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/nqy150

Associations of vitamin D with perinatal outcomes are inconsistent and few studies have considered the wider calcium metabolic system. We aimed to explore functional vitamin D deficiency in pregnancy by investigating associations between vitamin D status, parathyroid hormone (PTH), and perinatal outcomes. SCOPE (Screening for Pregnancy Endpoints) Ireland is a prospective cohort study of low-risk, nulliparous pregnant women. We measured serum 25-hydroxyvitamin D [25(OH)D] and PTH at 15 wk of gestation in 1754 participants. Mean ± SD 25(OH)D was 56.6 ± 25.8 nmol/L (22.7 ± 10.3 ng/mL) and geometric mean (95% CI) PTH was 7.84 pg/mL (7.7, 8.0 pg/mL) [0.86 pmol/L (0.85, 0.88 pmol/L)]. PTH was elevated in 34.3% of women who had 25(OH)D <30 nmol/L and in 13.9% of those with 25(OH)D ≥75 nmol/L. Whereas 17% had 25(OH)D <30 nmol/L, 5.5% had functional vitamin D deficiency, defined as 25(OH)D <30 nmol/L with elevated PTH. Elevated mean arterial pressure (MAP), gestational hypertension, pre-eclampsia, and small-for-gestational-age (SGA) birth were confirmed in 9.2%, 11.9%, 3.8%, and 10.6% of participants, respectively. In fully adjusted regression models, neither low 25(OH)D nor elevated PTH alone increased the risk of any individual outcome. The prevalence of elevated MAP (19.1% compared with 9.7%) and SGA (16.0% compared with 6.7%) were highest (P < 0.05) in those with functional vitamin D deficiency compared with the reference group [25(OH)D ≥75 nmol/L and normal PTH]. The adjusted prevalence ratio (PR) and RR (95% CIs) for elevated MAP and SGA were 1.83 (1.02, 3.27) and 1.53 (0.80, 2.93), respectively. There was no effect of functional vitamin D deficiency on the risk of gestational hypertension (adjusted RR: 1.00; 95% CI: 0.60, 1.67) or pre-eclampsia (adjusted RR: 1.17; 95% CI: 0.32, 4.20). The concept of functional vitamin D deficiency, reflecting calcium metabolic stress, should be considered in studies of vitamin D in pregnancy.The SCOPE pregnancy cohort is registered at http://www.anzctr.org.au as ACTRN12607000551493.