The average temperature of a normal healthy adult is 37°C. Temperature regulation is controlled by the hypothalamus, which is able to integrate temperature information from various parts of the body and provide physiologic responses to changes in temperature to maintain thermal homeostasis. While there are normal temperature changes based on diurnal rhythms, any temperature greater than 38°C is considered to be pathologically elevated. In the case of infection, it is thought that pyrogens released from either microorganisms or host white blood cells can increase the temperature set point of the hypothalamus or inhibit normal compensatory responses such as vasodilation. In pregnancy, the serum white blood cell count is often elevated representing an increase in immature leukocytes. As such, the pregnant patient is relatively immunocompromised and more prone to infection.
Worldwide, infection leading to sepsis and septic shock remains one of the most common causes of maternal morbidity and mortality. Fortunately, sepsis and its related complications are relatively rare. Overall rates of sepsis are generally thought to be about 0.3% of all pregnancies. Bacteremia is thought to affect only about 7.5 per 1000 pregnancies, with only about 10% of bacteremic patients going on to develop sepsis. There are several risk factors for maternal sepsis (Table 170-1). Emergency cesarean section appears to be the most important risk factor with rates of endometritis as high as 28%.
TABLE 170-1Risk Factors for Developing Maternal Sepsis |Favorite Table|Download (.pdf) TABLE 170-1 Risk Factors for Developing Maternal Sepsis
Emergency cesarean section
Prolonged rupture of membranes
Retained products of conception
History of pelvic infections
Greater than five vaginal examinations
Obstetric interventions (cerclage)
Pregnancy related infections are categorized into three main groups: (1) obstetric infections; (2) nonobstetric infections; (3) and nosocomial infections. Obstetric infections are further categorized based on trimester. First trimester infections are usually related to a miscarriage or surgical abortion. Second trimester infections are most commonly related to premature rupture of membranes while third trimester infections are associated with endometritis, perineal infections or surgical site infections. Nosocomial infections are commonly associated with intravenous lines, urinary catheters, and prolonged hospital stay.
The most common infections found in the obstetric population are as follows.
Chorioamnionitis is an infection of the placental membranes. It is generally considered to be a clinical diagnosis with classical signs including maternal fever (>38°C) without another known source, maternal or fetal tachycardia, uterine tenderness, and foul smelling amniotic fluid. It is much more commonly found in preterm pregnancies as compared to term pregnancies. Physiological changes within the vaginal epithelium that result in decreased pH and increased glycogen makes parturients particularly susceptible to genital tract infections. The overall incidence of chorioamnionitis in term pregnancies is generally thought to be about ...