You are consulted on a 29-year-old gravida 1 at nine weeks gestation with a two-year history of Type 2 diabetes and hypertension. She is admitted to the obstetric inpatient service for glycemic control. Although prescribed metformin and lisinopril, she ran out of both four months ago. Her current hemoglobin A1C is 9%. Her blood pressure is 140/90 mmHg in both arms, with an appropriately sized manual cuff while seated. She does not have retinopathy, nephropathy, or neuropathy. The obstetric team will begin weight-based insulin to achieve glycemic targets, and they ask for your input regarding blood-pressure management. How should one approach a pregnant patient with hypertension?
The most common chronic medical issue in reproductive-age women, essential hypertension (termed chronic hypertension in obstetric literature) contributes significantly to maternal and perinatal morbidity and mortality, primarily via increased risk of preeclampsia.
Chronic hypertension complicates up to 5% of pregnancies in the U.S., or as many as 120,000 pregnant women per year.1 Rates of chronic hypertension are expected to increase with later childbearing and increased rate of obesity. Prior to and during pregnancy, hypertension is defined as blood pressure 140/90 mmHg or higher. Chronic hypertension can be either hypertension diagnosed prior to pregnancy or elevated blood pressures identified prior to 20 weeks gestation.2 Normal pregnancy physiology leads to decreased systemic vascular resistance by the end of the first trimester, dropping systolic and diastolic blood pressure between 10 and 15 mmHg, with maximal effect mid-pregnancy followed by a gradual return to baseline.3 Therefore, chronic hypertension might be masked in early pregnancy. Normal changes in pregnancy include renal vasodilatation and increased glomerular filtration rate, so the average serum creatinine (SCr) is 0.5 mg/dL.4
Newly identified hypertension or accelerating hypertension after 20 weeks warrants close evaluation for preeclampsia. Preeclampsia is a multisystem, life-threatening disorder characterized by hypertension and proteinuria (greater than 300 mg/day). Severe forms of preeclampsia include HELLP (hemolysis, elevated liver enzymes and low platelets) syndrome and eclampsia (seizures with no other attributable cause). Superimposed preeclampsia occurs in 20% to 25% of women with chronic hypertension.5 Women with hypertensive target organ damage have an even greater likelihood of preeclampsia as well as maternal and fetal complications. Unfortunately, blood-pressure control during pregnancy has not been shown to minimize the likelihood of developing superimposed preeclampsia or associated maternal and fetal complications.6 The goal of antihypertensive management during pregnancy is to avoid acute maternal or fetal complications of severe hypertension.
Review of the Data
Q: How are hypertensive disorders of pregnancy classified?
The American College of Obstetrics and Gynecology and the National High Blood Pressure Education Program guideline committees have classified hypertensive disorders of pregnancy into four categories: chronic hypertension, preeclampsia, preeclampsia superimposed on chronic hypertension, and gestational hypertension.2,7