We read with interest the article by Cardonick et al that compared the results of 35 children who were exposed to chemotherapy in utero with 22 nonexposed children. The percentages of abnormal results on cognitive and behavioral assessment did not differ between the 2 groups, and the results were considered reassuring. To fully understand the results, we would like to address 3 issues.

First, 1 child who was exposed to chemotherapy in utero scored significantly low on both cognitive and school measurements and high (≥98% of peers) on 4 behavioral syndrome scales. Do the authors have more information on the severity and potential organ damage, eventually supported by brain computed tomography scan or magnetic resonance imaging? Moreover, it would be of interest to know whether these problems can be accounted for by other confounding factors (for example, obstetric complications) or may be related to prenatal exposure to chemotherapy.

Second, a remarkable finding in the study of Cardonick et al is the high cognitive mean scores on the IQ-tests (mean Full Scale Intelligent Quotient: 111.71 for the exposed group and 112.43 for the nonexposed group) and on the Bayley Scales of Infant and Toddler Development–III (111.43 for the exposed group and 118.13 for the nonexposed group). Compared with the norm of 100 and a standard deviation of 15, which is provided by the respective tests, the mean scores reported by the authors are almost 1 standard deviation above the norm.

Third, in the current study, mean gestational age at birth did not differ between the groups with normal (54/57) and abnormal (3/57) cognitive outcome. The authors conclude that premature birth did not predict developmental outcome. An interesting question is whether this conclusion also holds position when a predictive model is applied to the data. In literature, the long-term negative impact of prematurity on cognitive development has been demonstrated repeatedly.

We hope that these clarifications improve our insight in the long-term outcome and safety of prenatal exposure to chemotherapy.