BACKGROUND AND PURPOSE:

• Cooper et al. (Obstetrics & Gynecology, 2019) provides an update on Zika virus infection, specifically addressing the extent of risk for small-for-gestational-age (SGA), preterm birth, and lower birth weight of term neonates

METHODS:

• Retrospective observational study (2016)
  • New York City Health Department Bureau of Vital Statistics birth record data
  • Surveillance data for cases of Zika virus infection diagnosed in New York City residents
• Participants
  • Database includes all liveborn singleton neonates
• Primary exposure
  • Laboratory evidence of confirmed or probable Zika virus infection during pregnancy or peri-conception (6 weeks before LMP) or
  • Delivery of a neonate with congenital Zika virus infection
• Study design and data analysis
  • Zika virus infection determination based on reports to the New York City Health Department
  • Analysis was adjusted for maternal characteristics
  • Regression analyses were used to assess the risks of having an SGA neonate and delivering preterm
  • Association of infection with mean birth weight of term neonates was also assessed

RESULTS:

• 116,034 deliveries | Antenatal Zika virus infection identified in 251 (0.2%) | 20 neonates were diagnosed with congenital Zika virus (based on laboratory evidence)
• Women with antenatal Zika virus infection were more likely to be
  • Primiparous | < 20 years | Non-Hispanic black | Born outside of the US
• A higher percentage of women with Zika virus infection delivered an SGA neonate (11.2%) compared with those who were not infected (5.8%)
  • Adjusted relative risk (RR) 1.8 (95% CI, 1.3 to 2.6)
• There was no difference in preterm birth frequency for women with (8.8%) and without (7.8%) Zika virus infection
  • Adjusted RR 1.0 (95% CI, 0.69 to 1.6)
• Mean birth weight of term neonates was not significantly different for women with (3,256 g) and without (3,303 g) Zika virus infection
  • Adjusted mean difference: -41 g (95% CI, -94 to 12)
• Percent of neonates born SGA and preterm were similar for neonates with positive and negative Zika virus test results

CONCLUSION:

• Authors note limitations including
  • Study only included live births and Zika virus infection may cause fetal loss
• Women with antenatal Zika virus infection were
  • More likely to give birth to an SGA neonate
  • No significant differences in preterm birth rate or mean term birth weight were noted (although confidence intervals were wide)
• Zika virus may impact placental function and result in SGA even if there is no vertical transmission

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Learn More – Primary Sources:

Maternal Zika Virus Infection – Association With Small-for-Gestational-Age Neonates and Preterm Birth

Related ObG Topics:

CDC Guidance on Zika and Pregnancy

Zika Virus and Birth Defects: How Strong is the Correlation?

Is Prenatal Ultrasound Sufficient to Identify Zika Virus Brain Defects?

A Better Test for Zika?