Chapter 100: Maternal Emergencies After 20 Weeks of Pregnancy and in the Peripartum Period

INTRODUCTION

This chapter examines the diagnosis and treatment of the most important maternal emergencies occurring after 20 weeks of pregnancy and during the postpartum period. The second half of pregnancy is often characterized as ≥20 weeks of gestation for simplicity, but until 24 weeks, the chances of fetal survival are less than 50%. The postpartum period is generally accepted as the 6 weeks after delivery. Vast physiologic shifts in maternal cardiovascular tone occur as pregnancy progresses, highlighting the need for maternal blood pressure recordings and fetal heart tones during any ED visit. Conditions discussed are disorders associated with elevated blood pressure (hypertension, preeclampsia and HELLP syndrome [hemolysis, elevated liver enzymes, and low platelet count], and eclampsia); vaginal bleeding in the second half of pregnancy; premature rupture of membranes; peripartum cardiomyopathy; postpartum endometritis; and the emergency transfer of the pregnant patient.

DISORDERS ASSOCIATED WITH ELEVATED BLOOD PRESSURE: HYPERTENSION, PREECLAMPSIA AND HELLP SYNDROME, AND ECLAMPSIA

CHRONIC AND GESTATIONAL HYPERTENSION

The decrease in systemic vascular resistance results in a decrease in maternal blood pressure, and blood pressure reaches its nadir at 16 to 18 weeks of pregnancy. Blood pressure returns to prepregnancy values near the end of the second trimester. Almost 10% of pregnant women have hypertension; hypertension is preexisting in 1%, gestational hypertension without proteinuria develops in 5% to 6%, and preeclampsia develops in 2%.¹

Chronic hypertension in pregnancy is defined as a systolic blood pressure of ≥140 mm Hg or a diastolic blood pressure of ≥90 mm Hg that existed prior to pregnancy, is diagnosed before the 20th week of gestation, or persists longer than 12 weeks after delivery. Severe chronic hypertension is systolic blood pressure >160 mm Hg or diastolic pressure >110 mm Hg. Women with chronic hypertension are at increased risk for placental abruption, preeclampsia, low birth weight, cesarean delivery, premature birth, and fetal demise.^2,3

Gestational hypertension is hypertension present only after the 20th week of pregnancy or in the immediate postpartum period but without proteinuria.

Safe treatment options for hypertensive women who are pregnant are labetalol, methyldopa, nifedipine, and hydralazine.⁴ All antihypertensive drugs cross the placenta. Labetalol is the first-line agent for chronic hypertension in pregnancy.^3,5 The starting dose is 100 milligrams PO twice a day, and the usual maintenance dose is 200 to 400 milligrams PO twice a day. Methyldopa, used safely in pregnancy for decades, is started at 250 milligrams every 6 hours PO and titrated to achieve the desired blood pressure. The usual daily dose is 500 milligrams to 3 grams divided in two to ...