To evaluate the risk of acute and late side effects in children whose mothers received chemotherapy during pregnancy for hematological malignancies, we performed an analysis of 84 children with a long-term follow-up. The 84 children in our study were born to mothers with hematological malignancies (29 acute leukemia, 26 Hodgkin's disease, and 29 malignant lymphoma) who received chemotherapy during pregnancy, including 38 during the first trimester. These children were examined for physical health; growth; development; and hematological, cytogenetic, neurological, psychological, and learning disorders. The occurrence of cancer or acute leukemia in these children was also considered. Some of these patients have become parents, and their children were also considered in this analysis. In all of the children studied, including the 12 second-generation children, the birth weight was normal; learning and educational performance were normal; and no congenital, neurological, or psychological abnormalities were observed. With a median follow-up of 18.7 years (range, 6-29 years), no cancer or acute leukemia has been observed. These results confirm our previous reports, suggesting that if a pregnant patient has an aggressive hematological malignancy, chemotherapy at full doses can be safely administered, even during the first trimester, if cure of the hematological malignancy is considered reasonable.