So at first I though it was simply yet another paper ruling out a relationship between a type of drug and autism. But then there was this little line that caught my attention -
However, terbutaline exposure for > 2 days during the third trimester was associated with more than a fourfold increased risk for ASDs independent of indication although the limited sample size resulted in an imprecise and nonsignificant effect estimate (OR(adj) = 4.4; 95% confidence interval, 0.8-24.6).I didn't know what terbutaline was (or for that matter what a ß2 adrenergic receptor agonists was) but a four fold increase of autism is nothing to sneeze at. So I exercised my google Phd and went and found out that, in general, ß2 adrenergic receptor agonists are a class of drugs that are used to treat asthma and other lung problems and that terbutaline is just the name of a specific drug of this type.
But it turns out that terbutaline is/was also used, off-label, to delay preterm labor. So here you have a drug that has been used to delay preterm labor that might greatly increase the risk of autism. That definitely isn't good.
On the flip side, this result is based on a small number of cases so can't just assume that the relationship is going to be the same in the general population. But then again, this isn't the first study to suggest that neonatal exposure to terbutaline might increase the risk of autism.
Other studies have found that fraternal twins who were exposed to terbutaline for longer than two weeks had an increased chance of both having autism2, that rats who were exposed to a large dose of terbutaline showed signs of neuroinflammation3, and that certain forms of genes related to the beta2-adrenergic receptor might be more common in people with autism4.
So while there is some room for doubt, I think it is safe to say that the risk is real. Prolonged prenatal exposure to terbutaline probably does increase the risk of autism. The good news is (if any of this can be good) that the FDA issued a warning earlier this year about prolonged use of terbutaline for treating preterm labor -
The U.S. Food and Drug Administration is warning that terbutaline administered by injection or through an infusion pump should not be used in pregnant women for prevention or prolonged (beyond 48-72 hours) treatment of preterm labor due to the potential for serious maternal heart problems and death. In addition, oral terbutaline tablets should not be used for prevention or treatment of preterm labor. The FDA is requiring the addition of a Boxed Warning and Contraindication to the drug prescribing information (labeling) to warn against these uses.Hopefully the medical community will get the message.
1. Croen LA, Connors SL, Matevia M, Qian Y, Newschaffer C, Zimmerman AW. Prenatal exposure to ß2-adrenergic receptor agonists and risk of autism spectrum disorders. J Neurodev Disord. 2011 Aug 27. [Epub ahead of print]
PubMed PMID: 21874331 DOI: 10.1007/s11689-011-9093-4 (Open Access)
2. Connors SL, Crowell DE, Eberhart CG, Copeland J, Newschaffer CJ, Spence SJ, Zimmerman AW. beta2-adrenergic receptor activation and genetic polymorphisms in autism: data from dizygotic twins. J Child Neurol. 2005 Nov;20(11):876-84.
PubMed PMID: 16417856
3. Zerrate MC, Pletnikov M, Connors SL, Vargas DL, Seidler FJ, Zimmerman AW, Slotkin TA, Pardo CA. Neuroinflammation and behavioral abnormalities after neonatal terbutaline treatment in rats: implications for autism. J Pharmacol Exp Ther. 2007 Jul;322(1):16-22. Epub 2007 Mar 30.
PubMed PMID: 17400887 DOI: jpet.107.121483 (Open Access)
4. Cheslack-Postava K, Fallin MD, Avramopoulos D, Connors SL, Zimmerman AW, Eberhart CG, Newschaffer CJ. beta2-Adrenergic receptor gene variants and risk for autism in the AGRE cohort. Mol Psychiatry. 2007 Mar;12(3):283-91. Epub 2007 Jan 2.
PubMed PMID: 17199132 DOI: sj.mp.4001940