Effect of calcium supplementation on maternal hypertensive disorders and neonatal outcomes among pregnant Thai women: A 2-year interim analysis report

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Shina Oranratanaphan
Surang Triratanachat
Sukanya Chaikittisilpa
Patou Tantbirojn
Noppadol Chaiyasit
Unnop Jaisamrarn
Dhiraphongs Charoenvidhya


Background: Calcium intake is inversely correlated with hypertensive disorder in pregnancy. The amount of
daily calcium intake varies by country. Therefore, the effect of calcium supplementation may be different.

Objectives: The primary outcome was to evaluate the effect of calcium supplementation in hypertensive
disorder in pregnant Thai women. Secondary outcomes were to evaluate the side effects of calcium supplementation and the effects on delivering small for gestational age infants.

Methods: One hundred and sixty-two Thai women who visited the antenatal care (ANC) Clinic, King Chulalongkorn Memorial Hospital were enrolled. Patients were randomly allocated to Group A received ferrous sulfate (200 mg) and calcium carbonate (2 grams) per day. Group B received ferrous sulfate (200 mg) per day. Daily calcium intake from food and side effects of calcium supplementation were recorded. Maternal hypertensive disorders, neonatal morbidity, birth weight, and neonatal intensive care unit (NICU) admission were recorded and evaluated. The interim analysis was planned at a two year interval.

Results: The baseline characteristics were similar. Hypertension in pregnancy and delivery outcomes were not
different between both groups. Approximately half of the subjects received calcium had constipation (45.7%),
bloating (19.8%) and nausea (12.4%).

Conclusion: At the 2-year interval analysis, no risk reduction effects were observed for either hypertensive
disorder in pregnancy or for delivering small for gestational age infants. More than half of all calcium supplementation participants experienced side effects from calcium supplementation treatment such as constipation, bloating and nausea.

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