Risk factors for preterm delivery among early onset cancer survivors: A Finnish register-based study

Previous studies have shown an elevated risk for preterm delivery among early onset cancer survivors. Whether the preterm delivery starts spontaneously, due to possible uterine damage because of cancer treatment, or is induced due to maternal conditions is unclear. Our aim was to assess pregnancy related conditions in female cancer survivors possibly underlying the elevated risk for preterm labor. Nationwide cancer and birth registries were merged to identify 1,753 first deliveries of cancer survivors (diagnosed below 40 years of age) and 5,123 first deliveries of matched female comparison subjects between January 1991 and December 2013. Conditional logistic regression models were used to estimate the risk for pregnancy related conditions adjusting for maternal age, gestational age and smoking. We found an overall increased risk for hospitalization during pregnancy (OR 1.45, 95% CI 1.25-1.68), intrahepatic cholestasis (OR 2.86, 95% CI 1.09-7.49), fear of childbirth (OR 2.25, 95% CI 1.31-3.85) and mental disorders and diseases of the nervous system complicating pregnancy and labor (OR 5.89, 95% CI 2.31-15.00). Among survivors, 129 (7.4%) delivered preterm compared to 268 (5.2%) comparisons subjects (p = 0.004). We found a statistically significant increased risk for preterm delivery among cancer survivors with vaginal bleeding (OR 1.35, 95% CI 1.07-1.71) and pre-eclampsia (1.35, 95% CI 1.06-1.72) compared to comparison subjects with the same condition. Health professionals treating these women should be aware of these risks. In general, however, our results are reassuring when it comes to pregnancies among cancer survivors.