The risk of preterm birth and growth restriction in pregnancy after cancer.

It is unclear whether cancer and its treatments increase the risk of adverse pregnancy outcomes. Our aim was to examine whether cancer survivors have higher risks of poor outcomes in pregnancies conceived after diagnosis than women without cancer, and whether these risks differ by cancer type and race. Diagnoses from cancer registries were linked to pregnancy outcomes from birth certificates in three U.S. states. Analyses were limited to the first, live singleton birth conceived after diagnosis. Births to women without a previous cancer diagnosis in the registry were matched to cancer survivors on age at delivery, parity, race/ethnicity and education. Log-binomial regression was used to estimate risk ratios. Cervical cancer survivors had higher risks of preterm birth (Risk ratio = 2.8, 95% Confidence interval: 2.1, 3.7), as did survivors of invasive breast cancer (RR = 1.3, 95% CI: 1.1, 1.7) and leukemia (RR = 2.1, 95% CI: 1.3, 3.5). We observed a higher risk of small for gestational age (SGA) infants (<10% of weight for age based on a national distribution) in survivors of brain cancer (RR = 1.7, 95% CI: 1.1, 2.8) and extranodal non-Hodgkin lymphoma (RR = 2.3, 95% CI: 1.5, 3.6). We did not see an increased risk of infants born preterm, low birth weight, or SGA in pregnancies conceived after ductal carcinoma in situ, thyroid cancer, melanoma, or Hodgkin lymphoma. While our results are reassuring for survivors of many cancers, some will need closer monitoring during pregnancy.