1 - Maternal physiology and obstetrics

Summary

Overview of obstetrics

Obstetrics describes care related to pregnancy. In high-risk cases, such as maternal cardiac or renal disease, this may include pre-pregnancy care to optimise the mother's medical condition prior to conception. Care continues throughout the antenatal period, differing for women depending on their risk status (described in Chapter 2). Obstetric care then focuses on labour and delivery, and continues to the end of the postpartum period. During this time there are profound changes in maternal physiology. In addition, disorders may develop that are unique to pregnancy e.g. pre-eclampsia, obstetric cholestasis. An understanding of the changes in maternal physiology and the pathophysiology of pregnancy-related disorders is essential to provide safe, effective obstetric care.

Maternal physiology

There are many good textbooks describing the physiological changes occurring in pregnancy and these changes are beyond the scope of this book. This chapter summarises the implications these changes will have on anaesthetic practice.

Cardiovascular and haematological system

Changes to maternal cardiac physiology

• ↑ cardiac output (CO) (Figure 1.1), ↑ stroke volume, ↑ heart rate, ↓ systemic vascular resistance in pregnancy

• Left ventricular hypertrophy and dilatation

• Blood pressure alters throughout pregnancy (Figure 1.2)

Patients with pre-existing cardiovascular disease decompensate during pregnancy and may develop cardiac failure. Auto-transfusion due to uterine emptying at delivery causes ↑ venous return, which may precipitate cardiac failure in susceptible patients.

• Patients with cardiovascular disease need close monitoring and multidisciplinary care throughout their pregnancy with the involvement of obstetricians, anaesthetists, intensivists and cardiologists