Prevalence of microcephaly in Europe: population based study

Abstract

Objectives To provide contemporary estimates of the prevalence of microcephaly in Europe, determine if the diagnosis of microcephaly is consistent across Europe, and evaluate whether changes in prevalence would be detected using the current European surveillance performed by EUROCAT (the European Surveillance of Congenital Anomalies).Design Questionnaire and population based observational study.Setting 24 EUROCAT registries covering 570 000 births annually in 15 countries.Participants Cases of microcephaly not associated with a genetic condition among live births, fetal deaths from 20 weeks’ gestation, and terminations of pregnancy for fetal anomaly at any gestation.Main outcome measures Prevalence of microcephaly (1 Jan 2003-31 Dec 2012) analysed with random effects Poisson regression models to account for heterogeneity across registries.Results 16 registries responded to the questionnaire, of which 44% (7/16) used the EUROCAT definition of microcephaly (a reduction in the size of the brain with a skull circumference more than 3 SD below the mean for sex, age, and ethnic origin), 19% (3/16) used a 2 SD cut off, 31% (5/16) were reliant on the criteria used by individual clinicians, and one changed criteria between 2003 and 2012. Prevalence of microcephaly in Europe was 1.53 (95% confidence interval 1.16 to 1.96) per 10 000 births, with registries varying from 0.4 (0.2 to 0.7) to 4.3 (3.6 to 5.0) per 10 000 (χ2=338, df=23, I2=93%). Registries with a 3 SD cut off reported a prevalence of 1.74 per 10 000 (0.86 to 2.93) compared with those with the less stringent 2 SD cut off of 1.21 per 10 000 (0.21 to 2.93). The prevalence of microcephaly would need to increase in one year by over 35% in Europe or by over 300% in a single registry to reach statistical significance (P<0.01).Conclusions EUROCAT could detect increases in the prevalence of microcephaly from the Zika virus of a similar magnitude to those observed in Brazil. Because of the rarity of microcephaly and discrepant diagnostic criteria, however, the smaller increases expected in Europe would probably not be detected. Clear diagnostic criteria for microcephaly must be adopted across Europe.

Prevalence of microcephaly in an Australian population‐based birth defects register, 1980–2015

“…There are few published epidemiological studies of microcephaly, and comparisons are complicated by differences in case definition, period of ascertainment, pregnancy outcomes included, underlying population differences, and environmental variables. These difficulties were illustrated by a recent report of important variations in the prevalence of microcephaly recorded by 16 European birth defects registries 13 . In Australia, national estimates are difficult because of major differences between states in the scope of birth defects data collections 14 .…”

“…These difficulties were illustrated by a recent report of important variations in the prevalence of microcephaly recorded by 16 European birth defects registries. 13 In Australia, national estimates are difficult because of major differences between states in the scope of birth defects data collections. 14 The most recent national data (for births during 2002e2003), 2 which did not include data from the Northern Territory, found a lower prevalence of microcephaly (1.9 per 10 000 births) than we did.…”

Fetal microcephaly

“…The prevalence of prenatal microcephaly in Europe is 1.53 per 10 000,1 2.3 per 10 000 in India,2 and about 6 per 10 000 in the US 3. Identifying microcephaly is important because the smaller the fetal head circumference the greater the risk of developmental and intellectual delay 4…”

Congenital microcephaly hospitalizations in California infants: 1999–2013

“…Previously published reports of the incidence of microcephaly in diverse clinical settings have excluded from their analyses infants with microcephaly due to genetic syndromes or microcephaly in small for gestational age or premature infants. (Morris et al, ; Cragan et al, ; Centers for Disease Control and Prevention, , Centers for Disease Control and Prevention, , Graham, ). Currently, there are no universally adopted criteria to determine which additional comorbidities should be excluded for the epidemiologic tracking of the incidence of congenital microcephaly (to avoid potential microcephaly misclassification).…”