Residential Proximity to Zika Case Locations and Fertility Decline Among Married Couples in Singapore

Abstract

Objective Latin American regions with higher Zika-linked microcephaly caseloads have experienced steeper declines in fertility. However, there is little research on geographical variability of response within states or cities. Due to the short flight dispersal of the vector mosquito, outbreaks tend to occur in small localized clusters of diameters of less than one kilometer in urban settings. This study investigates whether fertility decline was greater in postal districts with publicly disclosed Zika cases compared to unexposed districts within the city state of Singapore. Methods Survey data were collected from 657 married women aged 25-34 to retrospectively identify timing of conception leading to live births or ongoing pregnancies, generating 14,578 person-month observations between January 2015 and December 2017. The effect of living in a postal district with known Zika cases was estimated using a fixed effects regression model. Findings Average monthly probability of conception fell during the Zika epidemic in both exposed and unexposed postal districts. Regression results suggest that the decline was not significantly greater in districts with known cases. Discussion Despite the localized nature of arboviral outbreaks in urban settings, the fertility response to perceived health threats posed by the Zika virus was city-wide. There is little evidence that public disclosures of outbreak locations led to a disproportionate response in affected neighborhoods.