Prediction of pregnancy-induced hypertension by means of the urinary calcium:creatinine ratio.

OBJECTIVE

To investigate the importance of the urinary calcium:creatinine ratio as a prognostic marker for pregnancy-induced hypertension.

DESIGN

A prospective study which measured the urinary calcium:creatinine ratio at 20-30 weeks' gestation. Patients' medical records were examined, blind to all urinary assay results, to determine the development of pre-eclampsia or gestational hypertension.

SETTING AND SUBJECTS

A first-morning urine sample was collected from 456 normotensive pregnant women, at 20-30 weeks' gestation, attending a hospital maternity outpatients' clinic for routine antenatal care.

RESULTS

The mean urinary calcium:creatinine ratio for women (n = 392) with a normotensive outcome of pregnancy, 0.52 (SD 0.32), was not significantly different from the ratios in those women who developed pre-eclampsia (n = 16), 0.49 (SD 0.32) or gestational hypertension (n = 48), 0.57 (SD 0.41). Significant risk factors for development of gestational hypertension, as estimated by logistic regression, were mean arterial blood pressure greater than 87.6 mmHg, Caucasian race, non-smoking and nulliparity.

CONCLUSIONS

Within the cohort studied, the calcium:creatinine ratio measured in asymptomatic women at 20-30 weeks' gestation was an unsatisfactory prognostic marker for development of pregnancy-induced hypertension. The major interpopulation, as well as intrapopulation, variation in calcium levels suggests that previous reported findings may not be readily generalised.