OTTAWA – A gestational age of less than 36 weeks, a relatively high serum level of uric acid, and a history of preeclampsia were all linked to progression of gestational hypertension to preeclampsia in a retrospective study of 280 women at one center.
The findings suggest that “clinical monitoring of these routinely available risk factors in pregnancies complicated by gestational hypertension could provide an easy, inexpensive, and helpful tool for identifying women with gestational hypertension who are at high risk of developing preeclampsia,” Yuquan Wu and his associates reported in a poster at the annual meeting of the Society of Obstetricians and Gynaecologists of Canada.
Gestational hypertension is usually the first clinical feature of preeclampsia, appearing before proteinuria. But it currently remains a challenge for physicians to predict if a woman who develops hypertension after 20 weeks' gestation will progress to preeclampsia, said Mr. Wu, a researcher in the department of ob.gyn. at the University of Montreal, and his associates in their poster.
They reviewed the medical records of all women who received obstetric care and gave birth at Ste-Justine Hospital in Montreal during March 2001-June 2003. They focused on women with a singleton pregnancy diagnosed with gestational hypertension without proteinuria at their initial hospital presentation.
Gestational hypertension was defined as a blood pressure at or above 140/90 mm Hg after 20 weeks' gestation.
Preeclampsia was diagnosed in women with gestational hypertension who also had proteinuria of at least 300 mg in a 24-hour urine collection, or a 1+ on dipstick urinalysis in two samples taken 6 hours apart. The review identified 91 women who reached term with gestational hypertension, and 189 women with preeclampsia. The average age of these women was 30 years.
In a multivariate analysis, each standard-deviation increase in the serum level of uric acid (56.1 micromol/L) boosted the risk of preeclampsia by 78%, and a history of preeclampsia boosted the risk of developing this complication in the current pregnancy by 3.4-fold. The risk of developing preeclampsia was reduced by 47% for each added week of gestational age.
Expressed in terms of dichotomous predictors, a serum uric acid level of at least 300 micromol/L at the first presentation of gestational hypertension raised the risk of preeclampsia 2.6-fold, and a history of preeclampsia raised the risk of a new case 3.2-fold.
Gestational age of less than 36 weeks when gestational hypertension was first diagnosed raised the risk of preeclampsia by 3.6-fold. The risk was elevated with a serum uric acid level of 300 micromol/L or greater even though this level is within the normal range (less than 350 micromol/L).
An additional analysis showed that women who presented with gestational hypertension but had no history of preeclampsia, had a serum uric acid level of less than 300 micromol/L at diagnosis, and were diagnosed at 36 weeks' gestation or after had a 20% risk of progressing to preeclampsia. In contrast, women with a history of preeclampsia who presented with hypertension before 36 weeks' gestation and had a uric acid level of at least 300 micromol/L had an 89% risk of progressing to preeclampsia.
These three markers predicted the risk of progressing from gestational hypertension to preeclampsia with a sensitivity of 82% and a specificity of 85%, Mr. Wu and his associates said in their poster.