Critical illness in pregnancy is relatively rare. Current studies estimate the incidence of intensive care unit (ICU) admissions in pregnancy and the puerperium to range between 0.7 and 13.5 events per 1000 deliveries (Pollock, 2010). Most of these admissions are postpartum, and obstetric complications account for between 55 and 90 percent. The most common indications are hypertensive disorders of pregnancy, hemorrhage, and sepsis (Baskett, 2008; Chantry, 2008; Orsini, 2012; Pollock, 2010). Nonobstetric indications for ICU admission include maternal cardiovascular disease, pulmonary disease, cerebrovascular accidents, trauma, and anesthetic complications (Wanderer, 2013; Zwart, 2010).
This chapter provides an overview of the most commonly seen conditions in the critically ill pregnant and postpartum woman. Moreover, some less common disorders that an obstetrician would be expected to be familiar with will also be briefly presented.
To understand maternal mortality rates, an understanding of the terms used to report maternal deaths is essential. The International Code of Diseases (ICD-10) and the World Health Organization (WHO) (2010) define maternal death as "the death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the duration and site of the pregnancy, from any cause related to or aggravated by pregnancy or its management, but not from incidental or accidental causes." A pregnancy-related death is defined as "the death of a woman while pregnant or within 1 year of termination of pregnancy irrespective of the duration or site of the pregnancy from complications of pregnancy, a chain of events initiated by pregnancy, or aggravation of an unrelated event or condition by the physiologic effects of pregnancy." Of other terms, the maternal mortality ratio (MMR) is the number of maternal deaths per 100,000 live births. The pregnancy-related mortality ratio is defined as the number of pregnancy-related deaths per 100,000 live births.
Globally, maternal mortality rates have been decreasing by 1.3 percent per year since 1990 (Kassebaum, 2014). In 2013, the global MMR was 209 deaths per 100,000 live births. This number was lowest—12.1—in the developed world. The highest ratio was seen in Western sub-Saharan Africa, where the MMR was 468.9. Globally, obstetric causes such as hemorrhage, hypertension, and sepsis were responsible for 72 percent of maternal deaths. Other indirect causes such as human immunodeficiency virus (HIV) and other preexisting conditions were responsible for 28 percent (Say, 2014).
In the United States, the pregnancy-related mortality ratio in 2013 was 18.5 deaths per 100,000 live births (Kassebaum, 2014). Despite a significant decline in the maternal mortality rate during the 20th century, the pregnancy-related mortality ratio has climbed since 1987, when the ratio was 7.2 (Berg, 1996; Creanga, 2015). It is unclear if this is a true increase in pregnancy-related mortality rates or whether this rise reflects improved ascertainment of cases. Examples include changes to death certificates and to insurance coding. Likely, it is from a combination of factors.