Pregnancy after cancer: Does timing of conception affect infant health?

BACKGROUND The objective of this retrospective cohort study was to determine whether women who conceive soon after treatment for cancer have higher risks of adverse pregnancy outcomes. METHODS Vital records data were linked to cancer registry diagnosis and treatment information in 3 US states. Women who conceived their first pregnancy after diagnosis between ages 20 and 45 years with any invasive cancer or ductal carcinoma in situ were eligible. Log‐binomial models were used to compare risks in cancer survivors who conceived in each interval to the risks in matched comparison births to women without cancer. RESULTS Women who conceived ≤1 year after starting chemotherapy for any cancer had higher risks of preterm birth than comparison women (chemotherapy alone: relative risk [RR], 1.9; 95% confidence interval [CI], 1.3‐2.7; chemotherapy with radiation: RR, 2.4; 95% CI, 1.6‐3.6); women who conceived ≥1 year after starting chemotherapy without radiation or ≥2 years after chemotherapy with radiation did not. In analyses imputing the treatment end date for breast cancer survivors, those who conceived ≥1 year after finishing chemotherapy with or without radiation had no higher risks than women without cancer. The risk of preterm birth in cervical cancer survivors largely persisted but was somewhat lower in pregnancies conceived after the first year (for pregnancies conceived ≤1 year after diagnosis: RR, 3.5; 95% CI, 2.2‐5.4; for pregnancies conceived >1 year after diagnosis: RR, 2.4; 95% CI, 1.6‐3.5). CONCLUSIONS In women who received chemotherapy, the higher risk of preterm birth was limited to those survivors who had short intervals between treatment and conception.Cancer 2018;124:000‐000. Cancer survivors who conceived their pregnancies more than 1 year after starting chemotherapy without radiation and 2 years after starting chemotherapy with radiation have no higher risks of preterm birth than a comparison group of women without cancer. The preterm birth risk is slightly higher in cervical cancer survivors who conceived within 1 year of diagnosis than for those who conceived >1 year after diagnosis.