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Facts and Artifacts About Anemia and Preterm Delivery

Ellice Lieberman, MD, DrPH; Kenneth J. Ryan, MD; Richard R. Monson; Stephen C. Schoenbaum
JAMA. 1990;263(9):1200-1201. doi:10.1001/jama.1990.03440090030018.
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To the Editor.—  Klebanoff et al,1 in the July 28 issue of JAMA, examined hematocrit and preterm birth to determine if that association is an artifact related to changes in maternal hematocrit during pregnancy. We appreciate their efforts in attempting to resolve this difficult issue. In our initial consideration of this problem,2,3 we also were concerned about possible artifact and examined the literature and our data to determine if changes in maternal hematocrit during pregnancy were a likely explanation for our results. In the literature, we did not find support for the substantial increases in hematocrit between 25 to 30 weeks and term suggested by Klebanoff et al. Several articles4-6 report changes of 1.1 percent or less between 25 to 30 weeks and term. Nilsen et al,7 who Klebanoff et al cite as noting larger changes, actually found maximum hemoglobin level increases of 5 g/L (a


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