Pregnancy and pregnancy outcomes after adolescent and young adult cancer in the AYA horizon study.

Lower birth rates and higher pregnancy loss are observed after childhood cancer. Studies specific to adolescent and young adult (AYA) cancer rarely have information on pregnancies that do not end in live birth, fertility preservation strategies, or detailed cancer treatment information to assess these risks. To address this gap, we examined pregnancy outcomes after cancer in a cohort of 30,020 AYAs with detailed clinical records. We identified 6021 survivors of AYA cancer matched to 23,999 AYAs without cancer enrolled in the Kaiser Permanente California health systems during 2004-2016. Of these, 950 survivors had ≥1 pregnancy during follow-up through 2018. Hazard ratios (HR) and 95% confidence intervals (CI) for pregnancy were estimated using multivariable subdistribution hazard models accounting for competing risks. Relative risks (RR) and 95% CIs for pregnancy loss were calculated with multivariable Poisson regression with generalized estimating equations. Pregnancy was less common after AYA breast (HR = 0.57; 95% CI: 0.50, 0.66) or gynecologic cancer (HR = 0.55; 95% CI: 0.42, 0.73) compared to AYAs without cancer. Among AYAs with cancer, some alkylating and platinum chemotherapy agents, but not gonadotoxic radiation, were associated with a lower likelihood of pregnancy. Use of assisted reproductive technologies was not common, and 69% of pregnancies after AYA cancer resulted in live birth. Pregnancy loss was not statistically significantly elevated for any cancer type. Among survivors, pregnancy loss was more common at older ages, with smoking during pregnancy, and among those who received cyclophosphamide. Our findings inform reproductive counseling and prenatal care for reproductive age cancer survivors.