Hypertension in pregnancy, which affects between 10-15% of pregnant women, is a growing problem because women are delaying pregnancy until later in life, thereby increasing hypertensive risk.1 It is a leading cause of maternal mortality worldwide.2 Renal disease in pregnancy is likewise increasing,1 but has not garnered much scientific attention.3
Education is necessary for understanding the physiologic changes that affect the kidney during pregnancy and the impact of hypertension on these changes.4 Palmer-Reis and colleagues1 address this gap in their article “Renal Disease and Hypertension in Pregnancy.” Their purpose is to “make physicians aware of the effects of pregnancy on these diseases” and to “review medications that avoid teratogenicity and optimize the disease prior to conception.”
Hypertension in Pregnancy
The authors discuss three categories of hypertension in pregnancy.
- Pre-existing hypertension is diagnosed prior to or early in pregnancy. The most common risk factors include increasing age, obesity, and insulin resistance. Close to one quarter of these patients may have superimposed preeclampsia.
- Pregnancy-induced hypertension, which can progress to preeclampsia, develops in the second half or pregnancy and resolves about six weeks after delivery.
- Preeclampsia is described by the authors as “a multi-system disorder, characterized by new-onset hypertension and proteinuria after 20 weeks’ gestation.”
Hypertension in pregnancy is defined as diastolic blood pressure (BP) >90 mmHg on two occasions, or one reading of >110 mmHg, or an increase in systolic BP of >15 mmHg above baseline.1 In preeclampsia, maternal BP should be maintained about 140/90 mmHg. Preeclampsia is the most common cause of acute kidney injury (AKI).1 A recent study of insurance claims of 26,651 hypertensive pregnant women found that those with hypertensive disorders were at high risk of end-stage renal disease, but the risk was much greater in women who had preeclampsia.5
Pathophysiology of Renal Disease in Pregnancy
Renal disease can predate pregnancy or be triggered by pregnancy, due to the stress that pregnancy places upon the kidneys. During pregnancy, there is a 50-percent increase in cardiac output1 and a 50-percent increase in circulating blood volume, leading to increased renal blood flow.6 Hormonal changes of pregnancy cause structural and functional changes in the kidney, such as increased kidney size and modified tubular function.1
Management of Comorbid Preeclampsia and Renal Disease During Pregnancy
The authors recommend:
- Pharmacologic agents (methyldopa, labetalol, nifedipine, hydralazine, amiodipine, and doxazocin) for treating preeclampsia, noting that angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) should be avoided. Intravenous labetalol or hydralazine may be indicated in severe hypertension (above 160/110 mmHg) if induced delivery is contraindicated.
- Avoiding “overzealous fluid resuscitation,” which places women at risk for pulmonary edema.
- Cautious use of nonsteroidal anti-inflammatory drugs (NSAIDs) and aminoglycosides, as they are nephrotoxins.
- Careful dosing of magnesium sulphate, which is the “standard obstetrical drug of choice” for treating and preventing comorbid preeclampsia and AKI.
- Antiplatelet therapy (eg, aspirin) for patients with risk factors such as older age (>40 years), obesity, previous personal/family history of preeclampsia, primiparity, long inter-birth interval, multiple pregnancies, pre-existing hypertension, chronic kidney disease (CKD), diabetes/gestational diabetes, and connective tissue disorders.