Following 11 Infants Born After Zika Infection in Pregnancy, Los Angeles County, 2016

Microcephaly and other birth defects have been found in babies born to women infected with Zika virus during pregnancy. Following CDC recommendations, the Los Angeles County Department of Public Health set up surveillance to check the health of such infants at birth and at 2, 6 and 12 months, including testing every one for Zika virus at birth. The county reported its results in CDC's Morbidity and Mortality Weekly Report.

The infants

In 2016, 11 infants were born in the county to women who met the national case definition for confirmed (four infants) or probable (seven infants) Zika infection. Nine were followed to 12 months; the parents of two, examined at birth, declined further participation.

• At their last assessments, all appeared healthy and normal, with normal head circumference.
• Zika IgM antibody testing of blood at birth, done for eight infants, was negative in every case. Three were also tested for Zika virus RNA in urine and blood, again all negative.

Moments of concern

None of the infants had clinical or laboratory evidence of Zika infection, but several cases raised worries along the way:

• Infant 1: Zika virus RNA was found in the umbilical cord at delivery, but the infant's IgM test was negative, and the baby was healthy at birth and every follow-up.
• Infant 4: a fetal ultrasound suggested "poor fetal brain development," but the mother's amniotic fluid tested negative for Zika RNA, the baby tested negative at birth, and was healthy at every visit.
• Infant 6: head circumference at birth (30 cm) was below the 3rd percentile for gestational age and sex, and microcephaly was diagnosed at one week. All Zika tests were negative, head size was normal at 2, 6 and 12 months, a cranial ultrasound at 3 months was unremarkable, and a pediatrician judged the child normal at a year.
• Infant 8: born at 38 weeks weighing 2.2 kg, with a head circumference (31 cm) below the 3rd percentile, the baby tested negative for Zika, was diagnosed with symmetric growth retardation and spent time in neonatal intensive care for breathing difficulty, but went home healthy at 4 days and had normal head size and health at 12 months.

What it means

The nine infants followed to a year showed no apparent harm. But subtler effects, or problems that appear later in life, would not be caught by this surveillance, and the findings may not apply to women with Zika who never sought care or who did not take part or complete follow-up. Continued monitoring of babies born after Zika infection in pregnancy remains important for understanding the virus's impact and guiding interventions.

Sources

• Curtis Croker, Amy Marutani, Marita Santos, Susan Hathaway and Bessie Hwang, "Notes from the Field: Follow-Up on 11 Infants Born to Women with Evidence of Zika Virus Infection During Pregnancy — Los Angeles County, 2016," Morbidity and Mortality Weekly Report, CDC: https://www.cdc.gov/mmwr/volumes/67/wr/mm6749a5.htm