Cancer Diagnosis During Pregnancy and Livebirth Outcomes in the Adolescent and Young Adult Horizon Study.

To describe patterns of cancer treatment and live birth outcomes that followed a cancer diagnosis during pregnancy. The Adolescent and Young Adult (AYA) Horizon Study is an observational study evaluating outcomes in survivors of the five most common types of cancer in this age group (15-39 years old). Of the 23,629 individuals identified diagnosed with breast, lymphoma, thyroid, melanoma, or gynecological cancer in North Carolina (2000-2015) and California (2004-2016), we identified 555 live births to individuals who experienced cancer diagnosis during pregnancy. Births to individuals diagnosed with cancer during pregnancy were matched ∼1:5 on maternal age and year of delivery to live births to individuals without a cancer diagnosis ( = 2,667). Multivariable Poisson regression was used to compare birth outcomes between pregnancies affected by a cancer diagnosis and unaffected matched pregnancies. Cancer diagnosis during pregnancy was associated with an increased risk of preterm delivery (prevalence ratio [PR] 2.70; 95% confidence interval [CI] 2.24, 3.26); very preterm delivery (PR 1.74; 95% CI 1.12, 2.71); induction of labor (PR 1.48; 95% CI 1.27, 1.73); low birth weight (PR 1.97; 95% CI 1.55, 2.50); and cesarean delivery (PR 1.18; 95% CI 1.04, 1.34) but not associated with low Apgar score (PR 0.90; 95% CI 0.39, 2.06). In our sample, 41% of patients received chemotherapy, half of whom initiated chemotherapy during pregnancy, and 86% received surgery, 58% of whom had surgery during pregnancy. Of the 19% who received radiation, all received radiation treatment following pregnancy. We identified an increased risk of birth outcomes, including preterm and very preterm delivery, induction of labor, low birth weight, and cesarean delivery, to those experiencing a cancer diagnosis during pregnancy. This analysis contributes to the available evidence for those experiencing a cancer diagnosis during pregnancy.