Hepatitis, HIV, herpes, HPV and parvovirus B19 in pregnancy

Overview

Viruses reach the baby in three ways: across the placenta (parvovirus B19), during birth through contact with blood or genital secretions (hepatitis B and C, HIV, herpes, HPV), and after birth through breast milk or close contact (HIV, hepatitis B).

Exam questions focus on screening, transmission rates, mode of delivery and newborn prophylaxis. Hepatitis A and E as causes of jaundice are covered in the jaundice chapter; rubella, CMV, varicella and toxoplasma are covered with TORCH infections.

Hepatitis B

Basics

• DNA virus, spread by blood and body fluids (sexual contact, shared needles, mother to baby).
• Incubation 6 weeks to 6 months; many carriers have no symptoms.
• Pregnancy does not make hepatitis B more common or more severe.

Serology

Transmission and risk

• Most transmission happens at delivery through contact with maternal blood.
• With no prevention, up to 90% of babies of infected mothers develop chronic infection, which leads later to cirrhosis and hepatocellular carcinoma.
• HBeAg-positive mother: about 85% of babies become carriers; e antigen negative: about 31%.

Management

• Screen all pregnant women for HBsAg at booking.
• Refer positive women to a hepatologist for liver assessment and long-term follow-up; test household contacts and partner.
• Specialists may add an antiviral (such as tenofovir) in late pregnancy when the viral load is very high; follow current guidance.
• Newborn: hepatitis B vaccine plus hepatitis B immunoglobulin (HBIG) as soon as possible after birth, within 12 hours. Immunoglobulin gives instant passive cover; the vaccine gives lasting active immunity. Together they prevent about 95% of transmission.
• Complete the vaccine course; in Pakistan, follow the national EPI schedule.
• Breastfeeding is allowed once the baby has had prophylaxis.

Hepatitis C

• RNA virus, spread mainly by blood (unsafe injections, transfusion, drug use, tattooing); sexual spread is very rare. It is common in Pakistan because of unsafe injection practice.
• About 80% of new infections are silent; it is a major cause of cirrhosis, liver cancer and liver failure.
• Vertical transmission about 3-5%, higher with a high viral load and up to 36% with HIV coinfection.
• Screening: not routine in the UK; offered to high-risk women (drug use, HIV or hepatitis B). Test anti-HCV antibody, then confirm with PCR for HCV RNA.
• Treatment: interferon and ribavirin are contraindicated in pregnancy (ribavirin is teratogenic); refer to a hepatologist and treat after delivery.
• Delivery: no routine caesarean; caesarean is advised if she also has HIV.
• Hepatitis C is associated with preterm rupture of membranes, gestational diabetes and low birthweight.

HIV

Basics

• RNA retrovirus, spread by sex, blood and mother to child.
• Vertical transmission happens mostly in late pregnancy, labour and delivery, and breastfeeding.
• Without intervention: 25-30% of babies infected. With full prevention: under 2% (as low as about 0.1-0.6% in well-resourced settings).

Screening

• Offer HIV testing to every pregnant woman at booking, with consent, counselling and confidentiality.
• Repeat testing for women at ongoing risk; rapid testing for women who arrive in labour unbooked. Women who decline can be offered testing again at 28 weeks.

Risk factors for transmission

• High maternal viral load (most important), low CD4 count, advanced disease.
• Prolonged rupture of membranes, preterm birth, invasive procedures.
• Breastfeeding.

Prevention of mother-to-child transmission

1. Antiretroviral therapy (ART) for the mother: start as early as possible, and by 24 weeks at the latest if not already on treatment; continue through labour. An HIV physician chooses the regimen.
2. Mode of delivery guided by the viral load at 36 weeks:

1. Newborn: ART (usually zidovudine) for 4-6 weeks; early cord clamping and bathing after birth.
2. Feeding: where safe formula is available (as in the UK), avoid breastfeeding regardless of viral load. In many low-resource settings, WHO-based national programmes support breastfeeding with maternal ART; follow the national guideline.

Diagnosing infection in the baby

• Maternal IgG antibody crosses the placenta, so antibody tests are positive in nearly all babies and are unreliable.
• Use PCR for viral nucleic acid at birth, around 3 and 6 weeks, and later.

Herpes simplex virus (HSV)

Basics

• Double-stranded DNA virus; HSV-2 causes most genital herpes, but HSV-1 is an increasing cause.
• After infection the virus stays latent in sensory ganglia and can reactivate.
• Primary episode: multiple painful shallow ulcers, fever, inguinal lymph nodes, sometimes urinary retention. Recurrences are milder.
• Diagnosis: swab for HSV PCR; type-specific antibodies help separate primary from recurrent infection.

Neonatal herpes

• Rare but severe; usually acquired during birth from infected secretions.

• Highest risk when the mother has a primary infection in the third trimester, especially within 6 weeks of delivery, because the baby is born before maternal antibodies cross.

Management

Human papillomavirus (HPV)

• DNA virus spread by sexual contact; infection is very common and usually subclinical.
• Types 6 and 11 cause about 90% of genital warts (benign).
• Types 16 and 18 cause about 70% of cervical cancer and many anal, vulval, vaginal, penile and oropharyngeal cancers.
• Vaccines: bivalent (16, 18), quadrivalent (6, 11, 16, 18) and nonavalent (adds 31, 33, 45, 52, 58). Best given before sexual debut; vaccination is usually deferred until after pregnancy.

Warts in pregnancy

• Warts often grow larger in pregnancy and may regress afterwards.
• Treatment in pregnancy is ablative only (cryotherapy, excision, laser); avoid podophyllotoxin and imiquimod in pregnancy.
• Caesarean is not done to protect the baby; it is needed only if warts block the birth canal or risk heavy bleeding.
• The baby may rarely develop recurrent respiratory (laryngeal) papillomatosis; caesarean has not been shown to prevent it.

Parvovirus B19

Basics

• Spread by respiratory droplets; common in school-age children (slapped cheek syndrome / fifth disease / erythema infectiosum).
• About 50% of women of childbearing age are immune. Teachers and nursery staff are most exposed.
• In adults it may be silent, flu-like, or cause symmetrical small-joint arthropathy.

Effect on the fetus

• Transplacental transmission 17-33%; the fetus is most vulnerable in the second trimester.
• The virus attacks red cell precursors, causing aplastic anaemia.
• Severe anaemia leads to high-output cardiac failure and hydrops fetalis (with liver congestion), and sometimes intrauterine death.
• Not teratogenic; it does not cause neurological damage. Survivors usually do well.
• Fetal loss: about 10% before 20 weeks, about 1% after 20 weeks.

Diagnosis and management

• Mother: IgM seroconversion; PCR for viral DNA in maternal blood or amniotic fluid is the most accurate test.
• Fetus: serial ultrasound for hydrops and middle cerebral artery (MCA) peak systolic velocity on Doppler; a raised MCA velocity means fetal anaemia.
• Hydropic, anaemic fetus: intrauterine (in utero) blood transfusion; many hydropic fetuses also recover spontaneously.
• No routine screening, vaccine or antiviral.

Summary of mother-to-baby transmission

Quick revision

• Hep B: screen HBsAg; HBeAg means high risk; baby gets vaccine + HBIG within 12 hours (95% protection); breastfeeding allowed.
• Hep C: 3-5% transmission (up to 36% with HIV); no ribavirin in pregnancy; no routine caesarean.
• HIV: ART early; vaginal birth if viral load below 50 at 36 weeks; caesarean if 400 or more; baby ART 4-6 weeks; PCR to diagnose.
• HSV: primary in third trimester (within 6 weeks) = caesarean; recurrent = vaginal; aciclovir from 36 weeks.
• HPV: 6/11 warts, 16/18 cancer; ablative treatment only in pregnancy.
• Parvovirus B19: aplastic anaemia, hydrops; MCA Doppler; intrauterine transfusion; worst before 20 weeks.

Written by The House Job from standard references (Obstetrics by Ten Teachers; Gynaecology by Ten Teachers).

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