(HealthDay)—Analgesics taken during pregnancy, including opioids, antimigraine drugs, and paracetamol, do not appear to cause asthma, according to a study published online March 17 in the European Respiratory Journal.

Seif O. Shaheen, Ph.D., from the London School of Medicine and Dentistry, and colleagues used linked Swedish health register data (492,999 individuals) to evaluate the relationship between various prescribed analgesics in pregnancy and the risk for childhood asthma/wheeze. In addition, negative paternal control and sibling comparison approaches were used to explore unmeasured confounding.

The researchers found that after they controlled for potential confounders, prescribed opioids, antimigraine drugs, and paracetamol were all positively associated with childhood asthma/wheeze risk at all ages (for example, odds ratios [ORs] for asthma/wheeze at 4 years were 1.39 [95 percent confidence interval (CI), 1.30 to 1.49], 1.19 [95 percent CI, 1.01 to 1.40], and 1.47 [95 percent CI, 1.36 to 1.59], respectively). Paternal control analysis did not support the presence of unmeasured confounding by genetics or shared environment. However, sibling comparison analysis suggested associations between prenatal exposure to opioids, antimigraine drugs, and paracetamol and /wheeze were confounded by specific maternal factors (ORs at 4 years, 0.91 [95 percent CI, 0.62 to 1.31], 0.5 [95 percent CI, 0.17 to 1.45], and 0.8 [95 percent CI, 0.5 to 1.29], respectively).

"We propose that analgesic use in pregnancy does not cause /, and that the association is confounded by unmeasured factors which are intrinsic to the mother, such as or anxiety," the authors write.