Chronic Hypertension In Pregnancy

Chronic hypertension in pregnancy is defined as hypertension present before pregnancy or at <20 weeks gestation.  Chronic hypertension carries significant risks of complications to both the mother and fetus, including the development of superimposed preeclampsia, fetal growth restriction, and preterm delivery.  However, with close surveillance and active management, most pregnancies result in a favorable outcome.

The physiological cardiac changes that occur in pregnancy to ensure adequate perfusion of the fetus also impact maternal blood pressure ( Table 1).  Beginning in the first trimester, systemic vascular resistance decreases in response to elevated progesterone levels, which trigger increased release of peripheral vasodilators (eg, nitric oxide, prostacyclin) and decreased vascular sensitivity to vasoconstrictors (eg, norepinephrine, angiotensin II).  The result is a decrease in systolic blood pressure of approximately 5-10 mm Hg and diastolic blood pressure of 10-15 mm Hg.  Blood pressure reaches its nadir in the second trimester before slowly returning to prepregnancy values in the third trimester.  The third trimester return to baseline is due to an increase in stroke volume and heart rate, which increases cardiac output to ensure sufficient blood flow to the fetus.