Treat chronic HT in pregnancy to avoid end organ damage. (May Not Prevent Preeclampsia).

SARASOTA, FLA. -- Treatment of chronic hypertension in pregnancy does not appear to prevent preeclampsia, but it can prevent end organ damage and should be considered in patients with a diastolic blood pressure greater than 100 mm Hg, according to Dr. James Martin.

The minimal threshold for treatment is blood pressure consistently above 140/90 mm Hg, and the absolute threshold is a diastolic blood pressure of at least 105 mm Hg, said Dr. Martin, who is professor of obstetrics and gynecology and director of maternal-fetal medicine at the University of Mississippi Medical Center, Jackson.

Blood pressure in these ranges has been shown to damage the vasculature, heart, and kidneys, and although it has not been linked with direct effects on the brain, it has been associated with an increased risk of stroke.

Of concern to both the mother and fetus, the uterus can also be affected; ischemia to the placenta can result and lead to placental growth retardation and intrauterine growth restriction (IUGR), Dr. Martin said at a perinatal symposium sponsored by Symposia Medicus.

In fact, perinatal morbidity and mortality rise in tandem with increases in maternal diastolic blood pressure above 90 mm Hg, he noted.

Treatment should be based on risk status. High risk is characterized by early severe hypertension (blood pressure greater than 160/110 mm Hg prior to 20 weeks' gestation), maternal age of over 40 years, a history of hypertension for 15 years or more, vascular or renovascular disease, antiphospholipid antibody positive status, and previous stillbirth.

High-risk patients require frequent prenatal visits, laboratory evaluations each trimester, an initial ultrasound to date the pregnancy followed by serial ultrasound beginning at 26 weeks, and delivery by 41 weeks in the absence of IUGR and preeclampsia. High-risk patients who develop preeclampsia require hospital admission.