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INTRODUCTION

Global fertility rates are predicted to drop significantly by 21001 but despite lower birth rates, there remains high maternal mortality worldwide. While the maternal mortality rate has declined since the turn of the century, approximately 810 women die of preventable pregnancy- and childbirth-related complications daily.2 Younger women and those residing in low- and middle-income countries have a disproportionately higher risk of maternal death. Meanwhile, globally, there has been a steady rise in women becoming pregnant later in their reproductive lives,3 particularly in higher-income countries. Together, this highlights significant inequities in the childbearing experience for women around the world. Increased maternal age is due to many factors, including more women in the workforce than ever before, and advances in assisted reproductive technology that have allowed women who might otherwise be infertile to achieve a pregnancy. Additionally, reproductive medicine now helps many women with chronic medical conditions to become pregnant. Consequently, pregnant women are now older and have more comorbid conditions than in past generations. Given the dramatic physiologic changes that occur during gestation, pregnancy can have significant clinical consequences especially among women with chronic cardiopulmonary disease.

Labor and delivery constitute a major hemodynamic and respiratory challenge; hence, women with either acute or chronic respiratory conditions need to be managed by a multidisciplinary healthcare team, which should include a pulmonologist. This multidisciplinary team should address medical and obstetric concerns, along with risks and benefits of anesthesia and analgesia, thereby ensuring appropriate management and anticipation of potential complications for both the mother and her newborn. This chapter addresses core pulmonary and cardiovascular physiologic concepts and then examines important, common clinical entities related to pulmonary and critical care diagnoses and clinical management in pregnancy.

THE PHYSIOLOGY OF PREGNANCY

While the normal physiologic changes of pregnancy are extensive, several areas are of central importance and are considered below. These include changes in respiratory and cardiovascular physiology, normal physiologic developments during labor and delivery, and determinants of fetal oxygenation and ventilation.

Respiratory Physiology

During pregnancy, the respiratory system undergoes changes throughout the respiratory tract. The effects of increasing levels of estrogen on the nasal mucosa can include edema, hyperemia, and glandular hypersecretion, which may result in gestational rhinitis, typically in the last few weeks of pregnancy.

The subcostal angle of the rib cage and the circumference of the chest wall increase4 and the diaphragm moves cranially about 4 to 5 cm.5 Diaphragm excursion does not decrease in pregnancy, despite the changes in chest wall configuration. However, due to the higher resting position of the diaphragm, the decreased downward pull of the abdomen, and the aforementioned chest wall changes, functional residual capacity (FRC) decreases by 20% to 30% by late gestation6 and declines further in the supine position (Table 96-1).7 The reduction in FRC may not be ...

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