It was with great interest that I read the report of Broussard and colleagues from the National Birth Defects Prevention Study, “Maternal treatment with opioid analgesics and risk for birth defects.” This well-done large study truly has the power to answer many questions about drug exposure and risks to the developing fetus. Obstetric providers are ever in need of up-to-date, accurate data to populate counseling discussions on medication use in pregnancy. The authors do a very nice job of reporting the results and the limitations of these types of studies. For instance, while the odds ratios are elevated, the absolute risks cannot be evaluated without a valid denominator in a case-control study. Other summaries report low absolute risks with opioid exposure.

It was interesting that only 66% of the women had their exposure linked to a specific reason they were taking the medication. It is disappointing that 1 in 3 women had no idea why they were taking a narcotic pain medication. I wonder if the authors considered excluding those women.

Because of the clinical need for adequate pain relief in pregnancy, recommendations usually include using the lowest effective dose for the shortest time needed. The current study states that drug dose, duration, and frequency of medication use were recorded in the database. However, these data are not incorporated into the analysis. Utilizing this powerful “exposure” information in the logistic regression model would provide clinicians a sense of the potential exposure needed to potentially raise the risk of birth defects. It may be that there is a threshold of exposure needed to increase the birth defect risk. For instance, if the main risk was only found in women who had been on the drug for a week or more, it would potentially reassure the obstetrician who needed to only prescribe opioids for a very short duration. This more complete model may be more informative for both providers and patients and help the counseling that must occur when prescribing needed medication to pregnant women.