Hypocalcuria as an early marker for pregnancy-induced hypertension

ABSTRACT

Recent studies using measurement of 24-hour urinary calcium have documented decreased excretion in women with pregnancy-induced hypertension [PIH]. However, most of these studies were performed late in pregnancy and not address the possibility of decreased calcium as a marker for PIH in first or early second trimester. This study aimed to determine whether an alteration in calcium excretion precedes the signs and symptoms of PIH. Three consecutive 24-hour urine specimens were collected from 111 women at 10 to 24 weeks, at 25 to 32 weeks and 33 weeks to term. Qualitative measurements of total calcium and creatinine were performed on all urine collection. Serum creatinine was measured, also. Normotensive nulliparous pregnant women attending the prenatal clinic were enrolled in this study. The women visited the prenatal clinic at intervals of 1-4 weeks. At each visit blood pressure was taken in the semi-sitting position and in the right arm with standard sphygmomanometer after a 3 minutes rest in comfort. PIH was defined as an increase in systolic pressure of at least 30 mmHg, a rise in diastolic pressure of at least 15 mmHg or an absolute pressure of at least 140/90 mmHg of at least two occasions of 6 hours interval in addition to significant proteinuria [at least 1 + dipstick or 300 mg per 24-hour urine]. The study was designed with 111 women. Eleven out of 111 [9.9%] developed PIH and 90.1% remained normotensive. 24-hour urine was collected at first, second and third trimesters of pregnancy. There was statistically significant hypocalciuria in hypertensive women in the three urine collections. The study revealed that hypocalciuria in PIH occurs early in pregnancy and it is concluded that determination of 24-hour urinary calcium could be used as a test for prediction of cases who could be liable to develop PIH. This hypocalciuria may be explained by a decrease in the glomerular filtration rate in PIH or it may be due to intrinsic renal tubular dysfunction