Infectious Diseases

• As with other diseases in pregnancy, one must think about the effect of an infectious disease on the pregnant woman and the fetus, as well as on the pregnancy outcome
• Infectious diseases discussed in this chapter

  • Common infections that increase or whose complications increase in pregnancy
  • Infections specific to pregnancy
  • Infections that can affect the fetus
• Urinary tract infection (UTI)

  One of the most common medical complication of pregnancy
• UTIs occur in up to 20% of pregnancies and account for as many as 10% of antepartum hospitalizations
• The prevalence of asymptomatic bacteriuria (ASB) in pregnant women ranges from 2% to 11%, with the majority of studies reporting 4% to 7%
• Women with asymptomatic bacteriuria (ASB) in early pregnancy are at a 20- to 30-fold increased risk of developing acute pyelonephritis during pregnancy as compared to pregnant women without bacteriuria
• ASB in pregnancy is further associated with preterm birth and low-birth-weight infants
• Untreated ASB will progress to cystitis or pyelonephritis in 25% to 40% of pregnant patients
• Before the advent of universal screening for ASB in early pregnancy, the reported rate of acute pyelonephritis in pregnancy was 3% to 4%; afterward, it was 1% to 2%
• Of the cases of pyelonephritis, up to 15% may be complicated by bacteremia, sepsis, or adult respiratory distress syndrome (ARDS)
• In pregnant women with sickle cell disease, the rate of ASB doubles to 10%, although recently it was shown that there is no increase risk in sickle cell trait carriers
• Factors contributing to higher incidence of cystitis and pyelonephritis in pregnancy

  • Smooth muscle relaxation effects of progesterone decrease bladder tone and cause ureteral and renal pelvis dilation, as well decreased ureteral peristalsis, resulting in physiologic hydronephrosis of pregnancy
  • Mechanical compression from the enlarged uterus can cause obstruction of the ureters, leading to stasis
  • Changes in the bladder including decreased tone, increased capacity, and incomplete emptying, all of which predispose pregnant women to vesicoureteral reflux
• Acute cystitis


  Distinct syndrome characterized by urinary urgency, frequency, dysuria, and suprapubic discomfort (tenderness on palpation) in the absence of systemic symptoms such as high fever and costovertebral angle tenderness
• Escherichia coli accounts for greater than 70% of all ASB and UTIs, and the remaining are caused by gram-negative enterobacteria (e.g., Klebsiella, Proteus) and gram-positive bacteria such as coagulase-negative Staphylococcus, group B Streptococcus (GBS), and Enterococcus
• Treatment of ASB and UTIs

  1. Initial treatment with amoxicillin, nitrofurantoin (Macrodantin), trimethoprim/sulfamethoxazole (Bactrim), or cephalexin

  2. Treatment duration of 3- to 7-day course of antibiotics

  3. Continuous nightly antibiotic prophylaxis recommended for women who have two or more UTIs during pregnancy
• Pyelonephritis


  The most common complication of a lower UTI, an ascending infection to the kidneys
• Pyelonephritis is estimated to complicate as many as 1% to 2.5% of pregnancies despite recommendations for universal screening for ASB
• The major risk factors for developing pyelonephritis are previous pyelonephritis and ASB
• Among pregnant women not receiving antibiotic prophylaxis to prevent acute pyelonephritis in pregnancy, recurrence has been noted to be up to 60%; conversely, in pregnant women on suppressive therapy, recurrence is less than 10%
• The most common organisms associated with acute antepartum pyelonephritis are E. coli (70%), Klebsiella-Enterobacter (3%), Proteus (2%), and gram-positive bacteria, including GBS(10%)
• Acute pyelonephritis


  Characterized by fever, chills, flank pain, dysuria, urgency, and frequency
• Pyelonephritis is not only a risk factor for preterm labor but also has particularly serious associated maternal complications including septic shock and ARDS
• Up to 20% of pregnant women with acute pyelonephritis develop multiorgan system involvement secondary to endotoxemia resulting in sepsis
• ARDS, the most severe complication of severe sepsis, develops in 2% to 8% of pregnant women with acute pyelonephritis
• Treatment of pyelonephritis during pregnancy

  1. Hospital admission, intravenous (IV) hydration, and IV antibiotics—often cephalosporins (cefazolin, cefotetan, or ceftriaxone) or ampicillin and gentamicin until the patient is afebrile and asymptomatic for 24 to 48 hours

  2. Transition to oral antibiotic regimen

  3. Treatment duration of 10 to 14 days of combined IV and oral antibiotics
• Bacterial vaginosis (BV) increases the risk for preterm premature rupture of membranes (PPROM), preterm delivery, and puerperal infections, including chorioamnionitis and endometritis
• Screening for BV in asymptomatic women is not routinely recommended
• Diagnosis of BV


  • Presence of thin, white or gray, homogeneous discharge coating the vaginal walls
  • Amine (or "fishy") odor noted with addition of 10% KOH ("whiff" test)
  • pH of greater than 4.5
  • Presence of more than 20% of the epithelial cells as "clue cells" on microscopic examination
• Treatment of BV in pregnancy

  1. Oral metronidazole (Flagyl) for 1 week

  2. Oral clindamycin for 1 week
• GBS is commonly responsible for UTIs, chorioamnionitis, and endomyometritis during pregnancy
• Early-onset neonatal sepsis occurs in 2 to 3 per 1,000 live births, with a mortality rate ranging from 2% to 50%, depending on GA at the time of delivery
• Various studies have demonstrated a wide range of asymptomatic colonization in pregnant women, from 10% to 35%
• To protect infants from GBS infections, widespread screening programs have been implemented
• Intravaginal forms of clindamycin

  Used for treatment of BV
• Oral form of clindamycin


  Preferred for pregnant women
• In pregnancy, because of high rates of asymptomatic infection and because treatment of high-risk patients may prevent adverse perinatal outcomes, a test of cure may be considered 1 month after treatment completion
• Group B Streptococcus (GBS)


  Commonly responsible for UTIs, chorioamnionitis, and endomyometritis during pregnancy
• GBS is a major pathogen in neonatal sepsis, which has severe implications
• Early-onset neonatal sepsis


  Occurs in 2 to 3 per 1,000 live births
• Mortality rate with GBS sepsis

  Ranges from 2% to 50%, depending on GA at the time of delivery