As part of the in vitro fertilisation treatment, ovarian stimulation is routinely performed. For this purpose, FSH preparations are used. Follitropin delta is a FSH preparation that is approved for a wide range of applications and is dosed individually according to body weight and serum anti-Müllerian hormone (AMH). Body weight is used to estimate the distribution volume of the glycoprotein FD in the patient and is thus a proxy of exposure. The AMH is used to estimate the ovarian reserve and thus the number of follicles in the ovaries that can be recruited by Follitropin delta stimulation. An algorithm is used for individual dosing. The aim of individual dosing is to reduce the probability of an under or overreaction of the ovaries to FSH therapy. In contrast to phase III registration studies, patients with severe overweight and underweight, as well as very high and very low AMH values and associated disorders of the menstrual cycle and oocyte maturation, are also found in the reality of care. The performance of the dosing algorithm and thus the results of ovarian stimulation in these subgroups of patients have so far been insufficiently investigated in the phase III registration trials. In the present study no statistical hypothesis will be tested. The study is descriptive by design and the analyses are descriptive and exploratory. NIS is chosen in order to explore how the individualized dosing regimen of REKOVELLE® performs in routine clinical practice and to investigate the effectiveness and safety of REKOVELLE® under real-world conditions. This is a monocentric, prospective, non-interventional cohort study conducted in normal care setting in a fertility clinic that will collect information from 850 women undergoing up to two cycles of IVF or ICSI treatment with controlled ovarian stimulation with REKOVELLE®.