Prevalence and Associated Factors of Neonatal Microcephaly in Thailand, 2014-2018

Microcephaly became of high concern after Zika outbreaks occurred worldwide. An estimation of its prevalence is crucial for public health preparedness and response. The objectives of this study were to estimate the prevalence of neonatal microcephaly in Thailand during 2014-2018, describe its epidemiological characteristics, and identify associated factors. This study was a cross-sectional study using data from the Health Data Center, Ministry of Public Health, Thailand. Neonatal microcephaly, as defined in this study, is a condition where a newborn has a head circumference (HC) less than the 3rd percentile of the International Fetal and Newborn Growth Consortium for the 21st Century standard head circumference charts for term newborn, and Fenton's growth charts for preterm newborn by gestational age and gender. Univariate and multivariate analysis were performed to identify associated factors. During 2014-2018, 121,448 newborns were identified and the prevalence of neonatal microcephaly was 14.5%. There were 9,871 boys and 7,687 girls. Multivariate analysis showed that small for gestational age (adjusted odds ratio (Adjusted OR) 5.34, 95% confidence interval (CI) 3.24, 8.81), birth length less than the 10th percentile (Adjusted OR 2.92, 95% CI 1.36, 6.29), elderly pregnancy (Adjusted OR 1.84, 95% CI 1.07, 3.18), and primigravida (Adjusted OR 2.01, 95% CI 1.37, 2.95) were significantly associated with neonatal microcephaly. The prevalence of neonatal microcephaly in Thailand was higher than expected. The international head circumference chart may not be suitable for Thai newborns suggesting that a head circumference growth standard for Thai newborns is needed.