Management of Chickenpox in First Trimester Pregnancy
For a pregnant woman diagnosed with chickenpox in her first trimester, intravenous acyclovir should be considered for serious complications like pneumonia, while oral acyclovir (800 mg 5 times daily) may be considered for symptomatic infection after careful discussion of risks and benefits, though the American Academy of Pediatrics has not recommended routine use due to unknown fetal risks. 1
Risk Assessment and Counseling
Women who develop varicella infection in the first trimester face a 0.5-1.5% risk of congenital varicella syndrome above baseline, which includes limb hypoplasia, cortical atrophy, chorioretinitis, and cataracts. 2
All pregnant women with chickenpox must be counseled about potential adverse maternal and fetal sequelae, risk of fetal transmission, and options for prenatal diagnosis. 3
The FDA classifies acyclovir as Pregnancy Category B, and a prospective registry of 749 pregnancies with first-trimester acyclovir exposure showed birth defect rates approximating the general population, though the registry size was insufficient for definitive conclusions. 1, 4
Treatment Algorithm Based on Disease Severity
For Mild to Moderate Chickenpox (No Pneumonia)
Oral acyclovir 800 mg five times daily for 5-7 days can be considered after thorough discussion with the patient about potential risks, as the AAP has not recommended routine use but states certain circumstances may justify it. 1
Treatment should ideally be initiated within 24 hours of rash onset for maximum benefit, as clinical trials show acyclovir reduces duration and severity of illness when started early. 1
Five days of therapy is sufficient, as controlled trials found no additional benefit from 7-day courses. 5
For Severe Complications (Pneumonia or Systemic Disease)
Intravenous acyclovir 10-15 mg/kg or 500 mg/m² every 8 hours for 5-10 days is recommended for varicella pneumonitis or other serious viral-mediated complications. 1, 3
Treatment should be started within 24-72 hours of rash onset for pneumonia. 3
Maternal admission to hospital should be seriously considered for any pregnant woman developing varicella pneumonitis, as this can be life-threatening. 3
Intravenous acyclovir during the second and third trimesters appears safe and may reduce maternal morbidity and mortality from varicella pneumonia. 6
Monitoring and Follow-up
Detailed ultrasound and appropriate follow-up is mandatory for all women who develop varicella in pregnancy to screen for fetal consequences of infection. 3
Serial ultrasounds should assess for signs of congenital varicella syndrome including limb abnormalities, microcephaly, and growth restriction. 2
Common Pitfalls to Avoid
Do not delay treatment while waiting for "adequate and well-controlled studies" - the FDA label acknowledges these don't exist, but the prospective registry data and clinical experience support use when benefits outweigh risks. 4
Do not assume treatment initiated after 24 hours is futile - while efficacy is greatest within 24 hours, some benefit may still occur when started between 24-72 hours, particularly for preventing severe complications. 1, 3
Do not withhold IV acyclovir for pneumonia due to pregnancy concerns - maternal death from varicella pneumonia is a real risk (14% mortality in one series), and IV acyclovir appears safe in later pregnancy. 6
Ensure adequate hydration during acyclovir therapy to prevent renal dysfunction. 4