Background
Acetaminophen is the most commonly used analgesic during pregnancy. Epidemiologic studies have raised concerns that prenatal acetaminophen exposure may affect offspring neurodevelopment, but evidence regarding prenatal acetaminophen use and offspring motor function remains limited. Therefore, we investigated whether prenatal acetaminophen exposure affected motor function in offspring.

Methods
We studied 734 mother–child pairs from the Danish National Birth Cohort (1996–2002) who participated in the Lifestyle During Pregnancy Study and completed motor function assessment using the Movement Assessment Battery for Children (MABC) at 5 years of age. The Total Impairment Score (TIS) ranges from 0 to 40, with higher scores indicating greater motor impairment. TIS was categorized using the 5th and 15th percentile cutoffs to define levels of motor impairment. We estimated odds ratios (ORs) across categories of motor function using multinomial logistic regression models. We estimated mean differences in continuous motor scores using multivariable linear regression. Models were adjusted for maternal socioeconomic and lifestyle factors, and the main indications for acetaminophen use.

Results
Prenatal acetaminophen use was not associated with motor function assessed by the MABC at age 5. Compared with never use, ever use was associated with an adjusted OR of 1.32 (95% CI: 0.90, 1.92) for abnormal motor function and 1.08 (95% CI: 0.65, 1.79) for borderline motor function. Results were similar when motor function was analyzed continuously (β = 0.54; 95% CI: −0.38, 1.46). Neither increasing duration nor cumulative exposure to acetaminophen during pregnancy demonstrated any consistent dose–response patterns. Findings were also null across sex-stratified analyses.

Conclusions
These findings did not support an association between prenatal acetaminophen exposure and the impairments of motor function measured at age 5.