What is the management for a pregnant woman at 20 weeks gestation exposed to measles with no evidence of immunity?

Management of Measles Exposure in Pregnancy at 20 Weeks

Administer immune globulin (IG) at 0.25 mL/kg intramuscularly (maximum 15 mL) immediately if the pregnant woman has no evidence of measles immunity and the exposure occurred within the past 6 days. 1, 2

Immediate Assessment and Intervention

Determine Timing of Exposure

• If within 72 hours of exposure: MMR vaccine would typically be the preferred post-exposure prophylaxis for non-pregnant individuals, but MMR vaccine is absolutely contraindicated in pregnancy due to theoretical teratogenic risks from live virus administration 3, 2
• If between 72 hours and 6 days of exposure: IG is the only appropriate intervention for this pregnant patient, as the window for vaccine effectiveness has passed and pregnancy precludes MMR use 1, 2
• If beyond 6 days: IG is unlikely to prevent infection, but close monitoring for measles symptoms should be instituted 1

Administer Immune Globulin

• Dose: 0.25 mL/kg intramuscularly (maximum 15 mL) for immunocompetent pregnant women 1, 2
• Timing: Administer as soon as possible within 6 days of exposure to prevent or modify measles infection 1, 2
• This passive immunization provides temporary protection and may prevent or attenuate disease severity 1

Understanding the Risks

Maternal Complications

• Pregnant women with measles face significantly higher risks than non-pregnant women, including increased hospitalization rates (21% vs 9% respiratory complications), severe pneumonia, and maternal death 4, 5
• Respiratory distress requiring intensive care is a major concern and can be fatal 6, 7

Fetal and Pregnancy Complications

• First and second trimester (including 20 weeks): Increased risk of spontaneous abortion, stillbirth, and fetal death due to placental infection and damage 4, 6, 8
• Studies show that 3 of 4 pregnancies before 24 weeks ended in spontaneous abortion or stillbirth when measles occurred 8
• Later pregnancy: Risks include preterm delivery, low birth weight, and congenital measles infection in the neonate 4, 5, 8
• Importantly, measles does not cause congenital malformations (unlike rubella), but placental histologic damage can lead to fetal death 6

Post-Exposure Monitoring

Clinical Surveillance

• Monitor for measles symptoms for 21 days after exposure (the maximum incubation period) 7
• Key symptoms include: fever, cough, coryza, conjunctivitis, followed by characteristic maculopapular rash starting on face and spreading cephalocaudally 3
• If measles develops despite IG prophylaxis, institute daily fetal monitoring during the 14 days following rash onset if the fetus is viable 6

If Measles Infection Occurs

• Provide supportive care only, as no antiviral therapy is available for measles 5
• Hospitalize if respiratory complications develop 4, 5
• Consider tocolysis if preterm labor occurs 6
• Implement strict airborne infection control measures to prevent nosocomial transmission 5, 7

Post-Delivery Vaccination Strategy

Immediate Postpartum Period

• Administer MMR vaccine before hospital discharge if the woman remains non-immune and has no other contraindications 3
• Postpartum vaccination is critical and could prevent approximately 40% of congenital rubella syndrome cases (and similarly protect against future measles exposure) 3
• Breastfeeding is not a contraindication to MMR vaccination 3

Timing After IG Administration

• If IG was administered during pregnancy, delay MMR vaccination until 5-6 months after IG administration to avoid interference with vaccine immunogenicity from passively acquired antibodies 1, 2, 9
• Counsel the patient to avoid pregnancy for 3 months after MMR vaccination 3

Critical Pitfalls to Avoid

• Never administer MMR vaccine during pregnancy, even within 72 hours of exposure—IG is the only option for pregnant women 3, 2
• Do not confuse measles (rubeola) with rubella (German measles)—they are different diseases with different risks; IG is not indicated for rubella exposure 1, 2
• Do not delay IG administration while awaiting serologic confirmation if clinical suspicion is high and exposure is documented 9
• Do not forget to vaccinate postpartum—failure to do so leaves the woman vulnerable to future exposures in subsequent pregnancies 3, 1
• Do not use the immunocompromised dose (0.5 mL/kg) unless the patient has documented immunocompromise; standard pregnancy does not require the higher dose 1, 2