Pregnancy during cancer treatment: A population-based analysis.

e12560 Background: We sought to assess maternal and neonatal outcomes of patients who became pregnant while undergoing treatment for cervical, ovarian, or breast cancer compared to those who were diagnosed following completion of treatment. Methods: We performed a population-based study of women aged 18-45 years diagnosed with cervical, ovarian, or breast cancer (from 2000 to 2015) and reported to the California Cancer Registry. Data were linked to California birth data to produce a database of individuals with cancer characteristics and birth outcomes. We included patients who had an estimated date of conception (EDC) within 6 months of starting radiation or chemotherapy treatment, as most chemotherapy treatments last 3-6 months. The primary outcome was preterm birth (PTB). Secondary outcomes included neonatal morbidity and severe maternal morbidity (SMM). Inverse probability of treatment weighting (IPTW) was applied to match cases and controls based on baseline demographic attributes, pregnancy, and medical comorbidities. Controls were composed of patients who had an EDC 6-12 months following radiation or chemotherapy start date, allowing comparison between “early” and “later” conception post-treatment. Logistic regressions were used to evaluate outcomes. Results: Twenty-three women with an EDC within 6 months of treatment (19 breast, 4 gynecologic) were matched to 68 controls, who conceived 6–12 months after treatment initiation (60 breast, 7 gynecologic). Rates of preterm birth (PTB) at 32–36 weeks (20.7% vs. 13.5%; OR 1.37, 95% CI 0.38–5.00, p=0.6) small-for-gestational-age (3.9% vs. 2.1%, OR 1.34, 95% CI 0.08–22.11, p=0.8) and SGA <10 th ; 16.0% vs. 8.5%, OR 1.29, 95% CI 0.23–7.29, p=0.8), neonatal morbidity (19.6% vs. 11.6% , OR 1.74, 95% CI 0.48–6.35, p=0.4), and cesarean delivery (35.9% vs. 30.9% , OR 1.13, 95% CI 0.41–3.16, p=0.8) were comparable between groups with no significant differences across outcomes. No cases of PTB before 32 weeks, severe maternal morbidity, or incidence of fetal demise were observed in either cohort. Conclusions: An EDC within 6 months of initiating chemotherapy or radiation was not associated with increased maternal or neonatal risk compared to conception at 6–12 months following treatment initiation. In the absence of the ability to perform randomized controlled trials on these patients’ populations, the results of our study help guide shared decision making for patients diagnosed with a pregnancy during cancer treatment. Odds ratios and P-values for maternal and neonatal outcomes across case and control group. Outcome OR (95% CI) P-value PTB < 32 weeks = Yes NA NA PTB 32-36 weeks = Yes 1.37 (0.38-5) 0.6297 SGA < 5%ile = Yes 1.34 (0.08-22.11) 0.8368 SGA < 10%ile = Yes 1.29 (0.23-7.29) 0.776 Fetal demise = Yes 1.09 (0.05-21.87) 0.9556 Severe maternal morbidity = Yes NA NA Neonatal morbidity = Yes 1.74 (0.48-6.35) 0.4024 Cesarean delivery = Yes 1.13 (0.41-3.16) 0.8101