AIM: The aim of this study was to examine how fever during pregnancy is associated with motor development in the child.

METHOD: This cohort study was based on data from females and their children, from the Danish National Birth Cohort, who took part in an 18-month and/or 7-year follow-up study. Information regarding fever (number of episodes, temperature, duration, and pregnancy week) was obtained around gestation week 12 and at the end of pregnancy. Assessments of motor development in early childhood were based on the ages at which the motor milestones 'sitting unsupported' (n=44,256) and 'walking unassisted' (n=53,959) were attained. The Developmental Coordination Disorder Questionnaire 2007 (DCDQ'07) was used to identify children with indication of developmental coordination disorder (DCD) at age 7 years (n=29,401). Any associations between the exposure to fever during pregnancy and motor development were estimated using Cox regression and logistic regression analyses.

RESULTS: Fever during pregnancy was reported by 15,234 (28.0%) participants in the 18-month follow-up and by 7965 (26.9%) participants in the 7-year follow-up. Adjusted analyses showed no association between prenatal exposure to fever and either 'sitting unsupported' or 'walking unassisted'. The proportion of children with indication of DCD was 3.1%. The odds ratio of indication of DCD if children were exposed to fever in utero was 1.29 (95% CI 1.12-1.49). However, no dose-response association was found.

INTERPRETATION: We found a significant association between maternal fever during pregnancy and DCD in children at age 7 years. The lack of a dose-response association might suggest that this association is explained by the underlying causes of the fever.