148 Chapter 8 injection (ICSI) in the future, and no sperm was found when testicular sperm extraction was performed. The other nine adolescents, aged 14.1-18.5 years, one at Tanner stage G4, the others at Tanner stage G5, with testicular volume 15-25 mL, stored semen that was of sufficient quality to be used for intrauterine insemination (n = 5) or ICSI (n = 4). DISCUSSION This study shows that many transgirls have an interest in FP indicating this is an important topic to discuss before starting treatment with GnRHa. Tools are being developed to facilitate such discussions. Strang and colleagues (2018) have developed a Transgender Youth Fertility Attitudes Questionnaire, and Johnson and colleagues (2016) have indicated that they aim to develop a modular decision aid. Most studies of FP by adolescents have been performed among cancer patients at risk for infertility and have shown that many decline FP because they do not want to delay the cancer treatment and because of severe illness and possibly costs (Burns, Boudreau, & Panepinto, 2006; Klosky et al., 2009). Two studies among transgender adolescents have also shown low uptake of FP (9%-14%) (Chen et al., 2017; Nahata et al., 2017). The use of FP in the present study is higher although still lower than the 51% of adult transgender women who stated that they would have made use of FP if it had been available (de Sutter et al., 2002). Thus, it will be important to see whether some of the transgirls who declined FP will regret their decision later in life. In the study of Strang and collagues (2018), about half of 25 transgender adolescents who completed a questionnaire about fertility attitudes indicated they felt that their feelings about wanting biological children might change when they were older. On the other hand, to our knowledge, there are no data available yet on the actual use of cryopreserved semen by transgender adults apart from a report of one individual who used her cryopreserved semen for donor insemination of her partner (Wierckx et al., 2012). The percentage of transgirls who did not wish to have children is similar to that reported by others (12%-37%) (Chen et al., 2018; Nahata et al., 2017; Strang et al., 2018). Previous studies in cisgender men showed a correlation between having a desire to have children and rate of sperm banking (Pacey et al., 2013). Such a correlation was not found in the present study, but in 57% of the medical files, information about the desire to have children was missing. In previous studies, more transgender adolescents stated they were interested in adopting children than in the present study, which raises the question if there might be a different view on adoption among adolescents in the United States compared with the Netherlands (Chen et al., 2018; Nahata et al., 2017).