Zika virus screening during pregnancy: Results and lessons learned from a screening program and a post-delivery follow-up analysis (2016-2022).

OBJECTIVE: To evaluate a Zika virus screening program applied to asymptomatic exposed pregnant women.

METHODOLOGY: Analysis of data generated during the roll out of a Zika screening program. We included socio-demographic data, ultrasounds, and serological results (IgM, IgG, and Plaque Reduction Neutralization Test; PRNT) from asymptomatic pregnant women exposed to Zika virus enrolled in the screening program between 2016 to 2019.

RESULTS: We included 406 asymptomatic ZIKV-exposed pregnant women who gave 400 full-term new-borns. The median age was 30 years (IQR = 25-34), which was lower (29 years; IQR = 24-34) among women of non-EU migrant origin (76.4% of the sample). Migrant women tended to delay the first pre-natal consultation compared to EU origin women (p = .003). Overall, 83.2% (N = 328) of participants had ZIKV low risk serological profile (IgM-/IgG- or IgM-/IgG+ and PRNT-), 3.0% (N = 12) showed high risk of recent ZIKV infection (IgM+ or PRNT+) and 13.7% (N = 54) had indeterminate results. A fetal malformation was identified in 29 children (9.3%). Fetal malformation was associated with a ZIKV high risk serological profile [24 out of the 246 (1.6%) with low risk profile and 3 out of the 12 with at high risk profile (25.0%; p = .02)]. Four newborns with high risk profile had a positive ZIKV-PCR test, which included two cases with microcephaly. No association was observed between maternal exposure to ZIKV infection and developmental abnormalities during the post-natal period follow-up.

CONCLUSIONS: The ZIKV-screening program had considerable costs and yielded a high rate of indeterminate results among asymptomatic pregnant women. Considering the poor value for decision-making of the results, efforts should focus on providing early access to routine maternity care, especially to migrant women. A simpler screening protocol might consider an initial ZIKV-PCR or IgM determination and subsequent referral to a fetal medicine specialist in those women with a positive result and/or whom ultrasound examination has revealed fetal abnormalities (10% of total women in our study sample).