How delaying pregnancy can decrease risk of microcephaly from Zika virus
Strategic delays when planning pregnancy may help mitigate birth defects caused by the Zika virus, according to results of an epidemiologic study published in Annals of Internal Medicine.
Researchers used a vector-borne Zika virus transmission model fitted to the epidemiologic data derived from 2015 to 2016 in Colombia. The intervention was recommendations to delay pregnancy by 3, 6, 9, 12, or 24 months, at different levels of adherence. Weekly and cumulative incidence of prenatal infections and microcephaly cases were measured.
The authors found that with 50% adherence to the recommendations to delay pregnancy by 9 to 24 months, the cumulative incidence of prenatal Zika virus infection was likely to decrease by 17% to 44%, whereas recommendations to delay pregnancy by 6 months or less were likely to increase prenatal infections by 2% to 7%. Researchers noted that delaying pregnancy could lead to women becoming pregnant during the peak of a Zika virus outbreak.
It was noted that sexual transmission of Zika virus was not explicitly accounted for in the model due to limited data, but it would be implicit in the overall transmission rate.
The investigators concluded that delaying pregnancy can have a substantial effect on reducing cases of microencephaly but it can exacerbate Zika outbreaks if the duration of the delay is insufficient. Several factors need to be carefully considered when promoting strategic delays, including the timing of initiation of the intervention, duration of the delay, and population adherence. “In the absence of a vaccine or therapeutic drugs for Zika virus infection,” the authors said, “a combination of mass and individual pregnancy-delay strategies with effective vector-control measures is needed to curtail the spread and burden of the ongoing outbreak in the Americas.”