Influence of Maternal Dietary Calcium Intake on Pregnanacy Induced Hypertension and Preterm Births

Abstract

Calcium intakes during pregnancy may play an important role in attenuating pregnancy induced hypertension(PIH) and in determining pre-term birth (<37 weeks of gestation). Routine calcium supplementation is in partadvocated for these reasons. The primary objective was to explore the relationship between dietary calcium,supplemental calcium and calcium rich food groups with pre-term births and to characterize the prevalence of PIHin a population that is routinely prescribed with calcium supplements. A cohort of 637 pregnant women wasprospectively studied at each trimester until delivery. Dietary intakes from a food frequency questionnaire,compliance to calcium supplement intake, presence of PIH, pre-eclampsia and birth outcomes at delivery wererecorded. Approximately 13.5% women were diagnosed with gestational hypertension (7.1% mild PIH, 5.5% PIHand 0.9% with pre-eclampsia). A higher proportion of pre-term babies were born to women with PIH (27.1%versus 7.3%; p<0.001) as compared to normotensive mothers. Mothers of pre-term babies had significantly lowerenergy adjusted calcium intakes ~87 mg/d (p=0.033) and calcium rich food groups ~141 g/d (p=0.012) in the 3rdtrimester of pregnancy as compared to the mothers of term babies. Similar trends for low calcium intake and lowcalcium rich food group intake was noted in women with PIH as compared to non PIH women. This studyhighlights that routine supplementation of calcium (1000 mg/d) may not abolish the inverse associations betweencalcium and calcium rich food group intakes with PIH and pre-term births. Substantiation of these findings would necessitate a re-examination of public health guidelines for pregnancy.