A 28-year-old pregnant woman from Tamil Nadu in her second trimester presents with fever, headache, and maculopapular rash. Serology confirms Zika virus infection. Which is the most common fetal complication associated with maternal Zika virus infection?

Explanation

## Fetal Complications of Maternal Zika Virus Infection **Key Point:** **Microcephaly** is the most common and most characteristic fetal complication of maternal Zika virus infection, particularly when infection occurs in the first and second trimesters. ### Congenital Zika Syndrome (CZS) — Clinical Features | Complication | Frequency | Timing of Infection | Severity | |---|---|---|---| | Microcephaly | Most common (50–80% of CZS) | 1st–2nd trimester | Severe; often with cortical abnormalities | | Cortical malformations | Very common | 1st trimester | Lissencephaly, polymicrogyria | | Retinal scarring/maculopathy | Common (40–50%) | 1st–2nd trimester | Atypical macular scarring | | Arthrogryposis/limb contractures | Less common (10–15%) | 1st–2nd trimester | Severe | | Cardiac defects | Rare (< 5%) | Variable | Mild–moderate | **High-Yield:** The **2015–2016 Zika epidemic in Brazil** established the causal link between maternal Zika infection and microcephaly. The risk of microcephaly is highest (up to 50–80%) when maternal infection occurs in the **first trimester**, with declining risk in 2nd and 3rd trimesters. ### Pathophysiology of Microcephaly 1. **Viral neurotropism** — Zika virus directly infects neural progenitor cells and cortical stem cells. 2. **Apoptosis and cell death** — massive programmed cell death of developing neurons, reducing cortical thickness. 3. **Impaired neurogenesis** — disruption of the radial glia and ventricular zone, limiting neuron production. 4. **Cortical malformations** — polymicrogyria, lissencephaly, and reduced brain volume. **Clinical Pearl:** Microcephaly in CZS is often accompanied by **severe cortical malformations, ventriculomegaly, and intracranial calcifications** (unlike other causes of microcephaly). Infants may also have developmental delay, seizures, and visual/hearing impairment. **Mnemonic:** **CZS = Cortex Zika Syndrome** — the brain (cortex) is the primary target organ. Remember: **Microcephaly > Macular scarring > Limb contractures** in frequency. **Warning:** Do not confuse Zika with Chikungunya (arthralgia, not birth defects) or dengue (hemorrhage, not congenital syndrome). Zika is the **only arbovirus of the three with a well-established teratogenic effect**.