TheMedical Board of California is telling physicians to warn women against the use of cannabis during pregnancy and lactation. Who will convey this finding about antacids (reported by Nicholas Bakalar)?

Using antacids during pregnancy is linked to asthma in offspring, a systematic review of research has found.

Researchers pooled data from eight observational studies and concluded that the risk of asthma in childhood increased by 34 percent when the mother used proton pump inhibitors and by 57 percent with the use of histamine-2 receptor antagonists. The study is in JAMA Pediatrics.

P.P.I.s and H2 blockers are considered safe and effective prescription drugs for treating gastroesophageal reflux disease, or GERD, a common complication in pregnancy. They are also available over the counter.

No observational study can establish causation, and genetic or environmental factors could explain the association. Yet even after controlling for maternal asthma, use of other drugs during pregnancy, age of the mother at birth, smoking and other variables, the association persisted.

The authors concluded: ” This study found associations between the use of acid-suppressive medications and antibiotics during the first 6 months of infancy and subsequent development of allergic disease. Acid-suppressive medications and antibiotics should be used during infancy only in situations of clear clinical benefit.”