Fetal programming of mental health by acetaminophen? Response to the SMFM statement: prenatal acetaminophen use and ADHD

Paracetamol use in pregnancy: Not as safe as we may think?

Paracetamol is used by more than 50% of women worldwide during pregnancy; headache representing the most frequent indication. Several studies report that long-term exposure to paracetamol in utero is associated with adverse neurodevelopmental outcomes in children, indicating a dose-response effect. However, less or no risk is found to be associated with short-term exposure. Paracetamol most likely crosses the placenta through passive diffusion, and there are several possible mechanisms for how paracetamol might affect fetal brain development. Although the literature suggests an association between prenatal paracetamol exposure and neurodevelopmental outcomes, the role of confounders cannot be ruled out. Consequently, as a precaution, we believe that pregnant women should be recommended ideally to only use paracetamol to treat conditions that might harm the fetus, such as severe pain or a high fever. This Comment aims to put focus on the potential fetal risks of paracetamol exposure in utero.

Paracetamol use during pregnancy - a call for precautionary action

Paracetamol (N-acetyl-p-aminophenol (APAP), otherwise known as acetaminophen) is the active ingredient in more than 600 medications used to relieve mild to moderate pain and reduce fever. APAP is widely used by pregnant women as governmental agencies, including the FDA and EMA, have long considered APAP appropriate for use during pregnancy when used as directed. However, increasing experimental and epidemiological research suggests that prenatal exposure to APAP might alter fetal development, which could increase the risks of some neurodevelopmental, reproductive and urogenital disorders. Here we summarize this evidence and call for precautionary action through a focused research effort and by increasing awareness among health professionals and pregnant women. APAP is an important medication and alternatives for treatment of high fever and severe pain are limited. We recommend that pregnant women should be cautioned at the beginning of pregnancy to: forego APAP unless its use is medically indicated; consult with a physician or pharmacist if they are uncertain whether use is indicated and before using on a long-term basis; and minimize exposure by using the lowest effective dose for the shortest possible time. We suggest specific actions to implement these recommendations. This Consensus Statement reflects our concerns and is currently supported by 91 scientists, clinicians and public health professionals from across the globe.

Behavioral Problems at Age 11 Years After Prenatal and Postnatal Exposure to Acetaminophen: Parent-Reported and Self-Reported Outcomes

Several studies have reported associations between prenatal acetaminophen exposure and behavioral outcomes in young children. We aimed to evaluate the associations of prenatal and postnatal exposures to acetaminophen with behavioral problems in children at age 11 years, using behavioral measures reported by parents and children. We studied 40,934 mother-child pairs from the Danish National Birth Cohort enrolled during 1996-2002. Parent-reported and child-reported Strengths and Difficulties Questionnaire (SDQ) responses were collected during the 11-year follow-up. We estimated risk ratios for behavioral problems including total difficulties as well as internalizing or externalizing behaviors following prenatal (during pregnancy) or postnatal (within the first 18 months after birth) acetaminophen exposure. Parent-reported and child-reported SDQ scores were moderately correlated; higher for externalizing (r = 0.59) than internalizing (r = 0.49) behaviors. Prenatal acetaminophen exposure was associated with 10%-40% higher risks for total difficulties and internalizing and externalizing problems based on parent- or child-reported SDQ, with the association being stronger for greater cumulative weeks of acetaminophen use. Postnatal exposure was associated with 16%-19% higher risks for parent-reported internalizing behaviors, but the associations were weak or null for child-reported scores except for prosocial behavior. Our study corroborates published associations between prenatal exposures to acetaminophen and behavioral problems and extends the literature to early adolescence.

Intrauterine Exposure to Acetaminophen and Adverse Developmental Outcomes: Epidemiological Findings and Methodological Issues

PURPOSE OF REVIEW

Acetaminophen (or paracetamol) is one of the most commonly used medications during pregnancy. We reviewed recent epidemiological evidence regarding intrauterine exposure to acetaminophen and risk for asthma, neurodevelopment disorders, and reproductive health in childhood.

RECENT FINDINGS

An increasing number of cohort studies have suggested that maternal use of acetaminophen during pregnancy was associated with increased risk for asthma; neurodevelopmental disorders, especially ADHD and behavioral problems; and genital malformations in the offspring. Oxidative stress and inflammation or endocrine effects are plausible shared biological mechanisms for the exposure to influence multiple developmental outcomes. We discussed methodological challenges that can threaten the validity of these observational data, including confounding and measurement errors. Novel statistical methods and research designs that can be used to mitigate these issues were introduced. Given the high prevalence of use, findings regarding intrauterine exposure to acetaminophen on multiple child health outcomes raise concerns. Research on causal and non-causal mechanisms that might explain these associations should be a priority.

Maternal acetaminophen use during pregnancy and childhood behavioural problems: Discrepancies between mother- and teacher-reported outcomes

BACKGROUND

Maternal acetaminophen use during pregnancy is common and has been associated with childhood behavioural problems among offspring, specifically hyperactivity and conduct problems.

OBJECTIVE

Assessments of child behaviour in many previous studies have relied on maternal or parent report. Acknowledging that results of behavioural assessments vary between informants, we examined the association between maternal acetaminophen use during pregnancy and behaviour problems in childhood based on mother- and teacher-report.

METHODS

A longitudinal study of 560 mother-child pairs with data on illnesses and medication use during pregnancy and neurodevelopmental assessments during childhood was conducted. Acetaminophen use during pregnancy was captured using a standardised maternal interview, completed 1 year after delivery on average. Measures of childhood (6-12 years of age) behaviour were obtained via mother- and teacher-report, using the Child Behaviour Checklist and Teacher Report Form. Linear and log-binomial models were used to calculate adjusted mean differences (MD) and risk ratios (RR), respectively and 95% confidence intervals (CI) for internalising, externalising, and total behaviour problems comparing acetaminophen users to non-users. Stabilized inverse probability weights were used to account for loss to follow-up, and adjustments for indication were made.

RESULTS

Approximately 60% (n = 354) of women reported use of acetaminophen during pregnancy. Acetaminophen use during pregnancy was associated with an increase in total behaviour problem score and risk of clinical behaviour problems according to mother report (MD 2.2, 95% CI 0.3, 4.1 and RR 1.93, 95% CI 0.99, 3.76) but not according to teacher report. Weighting to account for participation did not alter results, while adjustment for indications of acetaminophen use greatly attenuated the associations with mother-reported total behaviour problem score and risk of clinical behaviour problems (MD 0.1, 95% CI -2.1, 2.3 and RR 1.31, 95% CI 0.67, 2.58).

CONCLUSIONS

Acetaminophen use during pregnancy was weakly associated with mother-reported behaviour problems and not associated with teacher-reported problems.

Prenatal Exposure to Acetaminophen and Overweight in Childhood

OBJECTIVE

Acetaminophen (paracetamol), a medication commonly used in pregnancy, has hormonal effects, as has been suggested in experimental studies. Developmental exposure to endocrine disruptors could predispose individuals to weight gain. This study evaluated the associations between prenatal acetaminophen exposure and overweight in childhood.

METHODS

A total of 30,127 (age 7) and 24,934 (age 11) children in the Danish National Birth Cohort born during 1996 to 2002 were studied. Mothers reported acetaminophen use in telephone interviews conducted during pregnancy, and children's BMI and waist circumference were reported by parents at 7 and 11 years. Differences for BMI z score and waist circumference were estimated, as well as risk ratios for overweight in girls and boys adjusting for indications of use and other confounders.

RESULTS

There were no consistent associations found for prenatal acetaminophen exposure and BMI z score or waist circumference in girls and boys at both ages. Prenatal acetaminophen exposure was associated with overweight in girls at age 11 (risk ratio 1.31, 95% CI: 1.10-1.56, if exposed in all three trimesters; P < 0.001 for cumulative weeks of exposure), but no association was found in boys.

CONCLUSIONS

There was no strong association between prenatal acetaminophen exposure and childhood BMI, but the findings on frequent prenatal exposure to acetaminophen and overweight in girls warrant further investigation.

Association of maternal prenatal acetaminophen use with the risk of attention deficit/hyperactivity disorder in offspring: A meta-analysis

BACKGROUND

Acetaminophen is a widely used medication for fever and pain management during pregnancy. However, recent studies have found a possible connection between maternal prenatal acetaminophen use and attention deficit/hyperactivity disorder in children.

OBJECTIVE

We aimed to explore the association between maternal acetaminophen use during pregnancy and the risk of attention deficit/hyperactivity disorder in offspring.

DATA SOURCES

PubMed, Embase, Web of Science and Cochrane Library were searched from their initial publications through November 2018 for studies.

STUDY SELECTION

We included all studies that examined the association between maternal acetaminophen use during pregnancy and the risk of attention deficit/hyperactivity disorder in offspring if the authors reported odds ratios, risk ratios, hazard ratios, regression coefficient, standard error and 95% confidence intervals.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently extracted data on the definition of exposure and outcome, exposed, non-exposed and total number of participants in the sample population, adjusted potential confounders and outcome parameters. Study quality was also assessed.

RESULTS

Eight cohort studies with a total of 244,940 participants were included. Maternal exposure to acetaminophen during pregnancy increased the risk of attention deficit/hyperactivity disorder in offspring with a pooled adjusted risk ratio of 1.25 (95% confidence interval = [1.17, 1.34]). Children exposed prenatally to acetaminophen in the third trimester seemed to have the greatest risk of developing attention deficit/hyperactivity disorder (risk ratio: 1.26; 95% confidence interval = [1.08, 1.47]). In addition, a longer duration of maternal acetaminophen use during pregnancy was correlated with a higher risk ratio. Children whose mothers used acetaminophen for 28 or more days during gestation had a higher risk of developing attention deficit/hyperactivity disorder (risk ratio: 1.63; 95% confidence interval = [1.23, 2.16]).

CONCLUSION

There is an association between maternal acetaminophen use during pregnancy and the risk of attention deficit/hyperactivity disorder in offspring. The timing and duration of acetaminophen use during pregnancy may have a major effect on the risk of attention deficit/hyperactivity disorder.

Maternal Biomarkers of Acetaminophen Use and Offspring Attention Deficit Hyperactivity Disorder

Previous studies have suggested a positive association between self-reported maternal acetaminophen use during pregnancy and risk of attention deficit hyperactivity disorder (ADHD) in offspring. We sought to examine the prospective association between maternal plasma biomarkers of acetaminophen intake and ADHD diagnosis in the offspring. This report analyzed 1180 children enrolled at birth and followed prospectively as part of the Boston Birth Cohort, including 188 with ADHD diagnosis based on electronic medical record review. Maternal biomarkers of acetaminophen intake were measured in plasma samples obtained within 1–3 days postpartum. Odds ratios for having ADHD diagnosis or other developmental disorders were estimated using multinomial logistic regression models, adjusting for pertinent covariables. Compared to neurotypical children, we observed significant positive dose-responsive associations with ADHD diagnosis for each maternal acetaminophen biomarker. These dose–responsive associations persisted after adjusting for indication of acetaminophen use and other pertinent covariates; and were specific to ADHD, rather than other neurodevelopmental disorders. In the stratified analyses, differential point estimates of the associations were observed across some strata of covariates. However, these differences were not statistically significant. Maternal acetaminophen biomarkers were specifically associated with increased risk of ADHD diagnosis in offspring. Additional clinical and mechanistic investigations are warranted.

Prenatal exposure to acetaminophen and children's language development at 30 months

OBJECTIVE

To examine prenatal APAP exposure in relation to language development in offspring at 30 months of age.

METHOD

A population-based pregnancy cohort study including 754 women who enrolled in the Swedish Environmental Longitudinal, Mother and child, Asthma and allergy (SELMA) study in pregnancy week 8-13. Two exposure measures were used: (1) maternally reported number of APAP tablets taken between conception and enrollment; (2) APAP urinary concentration at enrollment. Language development at 30 months was assessed by nurse's evaluation and parental questionnaire, including the number of words the child used (<25, 25-50 and >50). Main study outcome; parental report of use of fewer than 50 words, termed language delay (LD).

RESULTS

59.2% of women enrolled in weeks 8-13 reported taking APAP between conception and enrollment. APAP was measurable in all urine samples and urinary APAP was correlated with the number of APAP taken during pregnancy (P<0.01). Language delay was more prevalent in boys (12.6%) than girls (4.1%) (8.5% in total). Both the number of APAP tablets and urinary APAP concentration were associated with greater LD in girls but not in boys. The adjusted odds ratio (OR) for LD among girls whose mothers reported >6 vs. 0 APAP tablets was 5.92 (95% confidence interval (CI) 1.10-31.94). The OR for LD in girls whose mothers' urinary APAP was in the highest compared to the lowest quartile was 10.34 (95% CI 1.37-77.86). While it cannot be ruled out, our available data do not support confounding by indication.

CONCLUSIONS

Given the prevalence of prenatal APAP use and the importance of language development, these findings, if replicated, would suggest that pregnant women should limit their use of this analgesic during pregnancy.