A 32-year-old pregnant woman from Tamil Nadu presents at 18 weeks gestation with a 3-day history of low-grade fever, maculopapular rash on face and trunk, mild arthralgia of wrists and knees, and conjunctival injection without exudate. She has no warning signs of severe disease. Serum IgM antibodies against Zika virus are positive. What is the most important counselling point for this patient?

Explanation

## Zika Virus in Pregnancy: Congenital Transmission Risk ### Clinical Diagnosis: Zika Virus Infection in Pregnancy **Key Point:** This patient has confirmed Zika virus infection (IgM positive) at 18 weeks gestation. The critical issue is **vertical transmission risk and congenital Zika syndrome (CZS)**, which includes microcephaly, intracranial calcifications, and neurodevelopmental sequelae. ### Zika Teratogenicity: Trimester-Specific Risk | Trimester | Risk of Congenital Zika Syndrome | Key Features | Management | |-----------|----------------------------------|--------------|-------------| | **First** | 15–20% | Microcephaly, cortical abnormalities, eye defects | Detailed ultrasound, amniocentesis at ≥18 weeks, counselling | | **Second** | 5–10% | Microcephaly, calcifications, growth restriction | Fetal assessment, PCR testing, close monitoring | | **Third** | <1% | Rare; mostly asymptomatic | Standard prenatal care | **High-Yield:** Zika infection in the **first trimester carries the highest risk** of microcephaly and congenital abnormalities. This patient is at 18 weeks (early second trimester) — still at significant risk (5–10%). ### Management of Zika in Pregnancy 1. **Confirm diagnosis:** IgM serology (positive here) + PCR if available 2. **Detailed fetal ultrasound:** Screen for microcephaly, intracranial calcifications, ventriculomegaly, growth restriction 3. **Amniocentesis:** Perform at ≥18 weeks gestation to detect fetal Zika RNA (PCR) - Positive amniocentesis = confirmed fetal infection - Negative amniocentesis = reassuring but does not exclude infection 4. **Counselling:** Discuss risks, testing options, and implications for delivery and neonatal care 5. **Delivery:** Vaginal delivery is safe; no indication for cesarean section for Zika alone **Clinical Pearl:** Amniocentesis should be performed ≥18 weeks because fetal urine (which contains Zika RNA) accumulates in amniotic fluid. Testing before 18 weeks has low sensitivity. ### Why NOT the Other Options? **Option 1 (Correct):** Addresses the primary concern — fetal risk and appropriate diagnostic testing. **Option 2 (Incorrect):** Zika in pregnancy is NOT benign. Congenital Zika syndrome is a well-established teratogenic effect with lifelong neurodevelopmental consequences. **Option 3 (Incorrect):** - No Zika vaccine is currently approved for use in pregnancy - Inactivated vaccines are theoretically safer in pregnancy, but no Zika inactivated vaccine exists - Vaccination would not prevent vertical transmission in an already-infected mother **Option 4 (Incorrect):** - Termination of pregnancy is NOT standard of care for Zika infection - Many infants born to Zika-positive mothers are unaffected - The decision to continue or terminate pregnancy is the mother's choice after informed counselling - In many countries, including India, termination is not routinely recommended ### Congenital Zika Syndrome Features **Mnemonic: ZIKA = Zygotic Infection → Intrauterine growth restriction, Keratitis, Arthralgia (in neonates)** Key manifestations: - **Microcephaly** (hallmark) — severe, with collapsed fontanelle - **Intracranial calcifications** — periventricular, basal ganglia - **Ocular abnormalities** — chorioretinitis, optic nerve hypoplasia, cataracts - **Arthrogryposis** — joint contractures - **Growth restriction** — intrauterine and postnatal - **Seizures and developmental delay** — long-term sequelae **Warning:** Do NOT reassure this patient that Zika is benign in pregnancy. The teratogenic risk is real and well-documented. [cite:Harrison 21e Ch 197; CDC Zika Pregnancy Guidelines 2023]