The study, conducted by the Department of Psychiatry and Behavioral Science at the University of Washington, found that pregnant women using aspirin "several times per week" had children whose IQ scores were 10.1 points lower for girls, and interestingly, only 1.3 points lower for boys. The researchers took into account potential confounding factors such as alcohol, smoking, caffeine use and educational background of parents. The testing was done at age 4 using the Weschler Preschool & Primary Scale of Intelligence (WPPSI).

Attention deficits were diagnosed using a standard "vigilance" testing procedure in which the child watched a large display of a Victorian house and was instructed to press a button whenever the silhouette of a cat appeared in a window. The aspirin-exposed children were found to make significantly more "errors of omission," which means the child forgot to press the button when the cat actually did appear in the window.

According to the researchers,

"IQ scores by age 4 years have a good predictive validity for later intellectual function. A 10-point IQ decrement is about two-thirds of a standard deviation, a sizable magnitude considering the number of related variables that have been adjusted for in this analysis. The finding that IQ was more differentially affected for girls compared to boys was a surprise and not a usual finding in behavioral teratology studies, in our experience. Attention decrements of the type measured in this study have been associated with learning disabilities in school-age children and with attentional deficits in the classroom, but only further follow-up of this sample would reveal the degree to which these children will sustain long-term behavioral and performance deficits associated with maternal aspirin use during pregnancy."

The results of this study are disturbing in that a very large percentage of women (46%) take aspirin during pregnancy. Also of interest, it was found that 41% of the women took acetaminophen (Tylenol) during pregnancy, however, acetaminophen was not found to cause any of the IQ or attention problems found with aspirin. These authors also listed three other studies which found exposure to aspirin during pregnancy inhibited learning, increased activity and caused developmental delays in test animals exposed to aspirin during pregnancy.

There were no changes observed in the growth measurements of weight, length and head circumference (34.5 cm) in the aspirin exposed children when compared to non-aspirin exposed children.

In conclusion, the researchers state,

SOURCE: Neurotoxicology and Teratology, 11:135-143, 1989

It has be well documented that using alcohol during pregnancy can interfere with neurological growth in the developing fetus. However, taking aspirin while also drinking appears to greatly increase the amount of damage to the developing brain states a report from the Alcohol and Brain Research Laboratory at the University of Iowa.

Evaluation of the neurotoxicity of these drugs was conducted by exposing 15 groups of pregnant rats to varying dosages of alcohol, aspirin and alcohol plus aspirin. Results showed that the mean total brain weight of the group treated with alcohol alone (no aspirin) was reduced 19.8%, relative to non-alcohol controls. Reduction in brain weight to the aspirin only group was not apparent in the total brain weight but was significant for the cerebellar weight at the highest aspirin dose of 50/mg/kg/day. (This highest aspirin dose would be equivalent to an average woman consuming between 9 or 10 aspirin tablets per day, although scientists stated the comparative dose would actually be smaller because rats metabolize aspirin faster than humans.

The highest dose of aspirin (50 mg/kg/day) caused a mean total brain weight 12.1% lower than the group treated with alcohol alone and 29.5% lower than the non-alcohol controls.

The researchers stated,

"Since the aspirin treatment alone had no significant effect on total brain weight, the worsening of the alcohol-induced microencephaly (small brain size) by aspirin appears to have been due to an interaction between aspirin and alcohol rather than merely an additive effect....