Hope for Motherhood: Pregnancy After Allogeneic Hematopoietic Cell Transplantation - a National Multicenter Study

• Successful pregnancies are possible among female alloHCT recipients, although birth rate is six times lower than in the general population

• Key factors increasing the chance of motherhood were younger age at HCT, non-malignant disease, no TBI or dose <8Gy and RIC/NMA conditioning

Improved long-term survival rates after allogeneic hematopoietic cell transplantation (alloHCT) make family planning for young adult cancer survivors an important topic. However, treatment-related infertility risk poses challenges. To assess pregnancy and birth rates in a contemporary cohort, we conducted a national multicenter study using data from the German Transplant Registry, focusing on adult women aged 18-40 who underwent alloHCT between 2003 and 2018. Out of 2,654 transplanted women, 50 women experienced 74 pregnancies, occurring at a median of 4.7 years post-transplant. Fifty-seven of these resulted in live births (77%). The annual first birth rate among HCT recipients was 0.45% (95%CI: 0.31 - 0.59%), which is more than six times lower than in the general population. The probability of a live birth 10 years after HCT was 3.4 % (95%CI: 2.3- 4.5%). Factors associated with an increased likelihood of pregnancy were younger age at alloHCT, non-malignant transplant indications, no total-body-irradiation (TBI) or a cumulative dose of <8 Gray, and non-myeloablative/reduced-intensity conditioning. 72% of pregnancies occurred spontaneously, with assisted reproductive technologies (ART) used in the remaining cases. Preterm delivery and low birth weight were more common than in the general population. This study represents the largest dataset reporting pregnancies in a cohort of adult female alloHCT recipients. Our findings underscore a meaningful chance of pregnancy in alloHCT recipients. ART techniques are important and funding should be made available. However, the potential for spontaneous pregnancies should not be underestimated, and patients should be informed of the possibility of unexpected pregnancy despite reduced fertility. Further research is warranted to understand the impact of conditioning decisions on fertility preservation.