Chapter 46 - Care of the peripartum patient

Summary

Introduction

Advances in medical care have led to increasing numbers of complex, high-risk, obstetric patients. With assisted reproductive technology, women at older maternal ages with medical comorbidities are able to conceive. Internists are often consulted to assist or even primarily manage pregnant women with preexisting medical disease or conditions that develop during pregnancy. This chapter will focus on several of the most common conditions that are unique to pregnancy or that occur due to the physiologic changes during the gestational period.

Cardiovascular

Cardiovascular changes in pregnancy occur predominantly in the first trimester, plateau in the second trimester, and then peak again around the time of labor and delivery. One of the earliest changes seen is a fall in systemic vascular resistance (SVR), reaching its nadir at 14–24 weeks of gestation, and then rising at term [1]. The early fall in SVR relates to peripheral arterial vasodilation, mediated by progesterone and perhaps nitric oxide [2]. In response to falling SVR, the heart rate rises, up to 20% by the third trimester [3]. An increase in heart rate leads to decreased time for diastolic filling and can lead to reduced cardiac output (CO) and perfusion pressures. In the first trimester CO rises and peaks by the end of the second trimester at approximately 30–50% over non-pregnant values. It rises again at the onset of labor, and declines rapidly after delivery [1]. Finally, blood pressure (a product of CO and SVR) falls by approximately 10% in early pregnancy, returning to normal pre-pregnancy values around term [4].