To the Editor: In their cohort study of more than 1 million Norwegians identified from the Medical Birth Registry, Dr Swamy and colleagues1 reported that preterm birth was associated with diminished long-term survival and reproduction. These findings are consistent with a growing body of evidence supporting the hypothesis of a fetal or developmental origin of adult disease.2 However, we are concerned that the results could be confounded by a more dominant influence of low birth weight, which often accompanies preterm birth.
Liew G, Wang JJ, Mitchell P. Preterm Birth, Long-term Survival, and Fertility. JAMA. 2008;300(2):167-168. doi:10.1001/jama.300.2.167-a