Study Population
We assembled a cohort of females with at least one pregnancy episode and had continuous enrollment from 30 days before pregnancy start date to 6 weeks after pregnancy end date, allowing for multiple pregnancy episodes per female. We used an algorithm that was developed and validated in multiple U.S. and U.K. administrative databases.20Claims for pregnancy markers, procedures and outcomes were identified from diagnosis, procedure, DRG, HCPCS, and laboratory test codes (Table S1).20-24 First, pregnancy outcome was assigned to each pregnancy episode. Pregnancy end dates were assigned using the first occurrence of the most reliable outcome code. Pregnancy start dates were then estimated using gestational age claims and pregnancy markers. Live birth episodes were retained for this analysis. We linked mothers and newborns by matching on the offspring’s earliest date of insurance coverage within 10 days of the mother’s live birth claims code.25 Mother-to-infant linkage was successful for 90% of live births and did not differ by maternal cancer status. Mothers without a matched infant were retained in the dataset. Plurality was determined by number of infants matched to each pregnancy episode. (Table S1).
We assembled a cohort of female AYA cancer survivors querying for cancer codes (Table S2),26 excluding non-melanoma skin. We required > 2 diagnostic codes pertaining to the same cancer site within 12 months.27 To identify new cancer diagnoses, we required an observed 6-month period of continuous enrollment without another cancer diagnosis prior to the index cancer diagnosis claim date. We retained those of AYA age (15-39) at first cancer diagnosis claim.
Merging the pregnancy and AYA cancer survivor cohorts, we generated a cohort of AYA cancer patients and females without AYA cancer who delivered live births (eFigure 1). For live births in AYA cancer survivors, pregnancy start dates that occurred after the index cancer diagnosis claims date were considered exposed. We retained the first live birth after cancer diagnosis for AYA cancer survivors and the first live birth episode in the dataset for each female without cancer that occurred between the ages 15-50 years of age.