In this follow-up study, ICSI and SC children show a comparable cognitive and motor development until the age of 8 years.

In this follow-up study, ICSI and SC children show a comparable cognitive and motor development until the age of 10. These findings are in line with those obtained at age 8.

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Study question In Belgium, by law, a retention period of 10-years is standard. Is this period sufficient for women to return to the clinic and use their vitrified oocytes? Summary answer A standard cryopreservation period of 10-years seems sufficient since half of the women returned to the fertility clinic and 96% used the vitrified oocytes. What is known already The main driver for elective oocyte cryopreservation is to buy more time to find a suitable partner. The question remains whether 10 years of cryopreservation is sufficient for women to accomplish their goal of finding a partner and procreate with or without using their vitrified oocytes. The return rates and the utilisation rates of the vitrified oocytes reported in the literature are low. Most women do not use their vitrified oocytes. Little is known about women's reproductive pathways after EOV and the destination of the expired surplus vitrified oocytes. Study design, size, duration Computerized clinical data were retrieved from a pioneer cohort of women who underwent EOV in our centre for age-related reasons more than 10 years ago (between 2009 and 2012). Hence, the legal cryopreservation period of their oocytes expired between 2019 and 2022. We documented reproductive choices for those who returned to the centre and we investigated the intended destination of the expired vitrified oocytes for those who did not return. Participants/materials, setting, methods Data were collected from clinical charts of women who vitrified oocytes. According to Belgian law, unused vitrified oocytes expire when reaching the age limit of 48 years for use or by reaching the standard cryopreservation period of 10 years. We evaluated whether women eventually started treatment, assessed their relational status, the utilisation rate of the vitrified oocytes and the intended destination of the vitrified oocytes as stated in their informed consents. Main results and the role of chance 117 women vitrified their oocytes at least 10 years ago. Women's oocyte cryopreservation period expired because they were either beyond the age limit for use (n = 82) or because the legal oocyte cryopreservation period of 10 years was reached (n = 35). Five women requested transport of their oocytes for treatment in a centre abroad. Fifty-two out of 117 women (44.4%) returned for assisted reproduction. Eventually, 96% (50/52) of them used their vitrified oocytes for treatment and 21/50 had a child or ongoing pregnancy. Upon return to the clinic, 22 women were single and 27 had found a partner, two women returned with a co-parent and one woman had a female partner. Furthermore, 7/117 women returned to the clinic but eventually refrained from treatment. Fifty-one women never returned to the centre. Only five women asked to prolong the cryopreservation period for medical reasons. The others not using their vitrified oocytes, did not initiate further action concerning the cryopreservation period, use or destination of their stored oocytes. Hence, the destination of the cryopreserved oocytes was according to the women's choice stated in the informed consent. The majority donated their oocytes for research (60%), others (31%) opted to destroy the oocytes after 10 years of cryopreservation. Limitations, reasons for caution It was not possible to map out the reproductive pathway of women who did not return to the centre and whose vitrified oocytes expired for use. Follow-up of reproductive choices and outcomes in women who did not return for treatment is required for a comprehensive appraisal of EOV. Wider implications of the findings The vast majority of the women who returned for treatment used their vitrified oocytes. Those not returning did not initiate further action concerning the use or destination of their vitrified oocytes. These results add to our knowledge on the utilisation rate after EOV, essential to improve counselling of future EOV-candidates. Trial registration number not applicable

Study question Do children born in oocyte donation families perceive their relationships with their parents differently than children conceived trough ICSI? Summary answer No significant differences were found in the family relationships between children born in oocyte donation families (OACC) compared with controls (ICSI). What is known already Majority of the previous research concerning relationships in families using oocyte donation focused on the mothers’ perspective. Little is known about how children in these families view their family relationships. Studies investigating young children’s perspectives in donor-families (5-10 years old) indicate good parent-child relationships (Imrie, et al., 2021; Blake, et al., 2013; Casey, et al., 2013). Few of these studies involve young children conceived using anonymous oocyte donation. Study design, size, duration This study included 17 children born through anonymous oocyte donation in heterosexual parents and a comparison group of 13 children conceived ICSI using the heterosexual parents’ own gametes. Data were collected between August 2021 and January 2023. The sample is part of a larger ongoing case-control-study investigating family relationships and the wellbeing of both parents and their children in families created by anonymous oocyte donation. Participants/materials, setting, methods Children were 5 to 7 years old (M = 6.13; SD = 0.5) and had been born after assisted reproduction (ICSI with or without using anonymous oocytes) with their two heterosexual parents. All children were invited to the hospital to undergo biomedical and psychological testing, including the Family Relationship Test (FRT; English version: Bene and Anthony, 1985; Dutch version: Baarda and van Londen, 1985). Multiple blind evaluators were used. Main results and the role of chance No significant differences were found between children born in oocyte donation families (OACC) compared with controls (ICSI). Two-sampled-T-tests show no significant differences for (1) positive feelings (towards and received by children) to their mothers (OACC: M = 6.65, SD = 4; ICSI:M=8.85, SD = 4), fathers (OACC: M = 5.06, SD = 0; ICSI: M = 5.08, SD = 0) or themselves (OACC: M = 0.35, SD = 0.5; ICSI: M = 0.77, SD = 0), (2) negative feelings (towards and received by children) to their mothers (OACC: M = 1.47, SD = 0.5; ICSI: M = 1.92, SD = 4), fathers (OACC: M = 2.06, SD = 0; ICSI: M = 2.31, SD = 0.5) or themselves (OACC: M = 0.76, SD = 0; ICSI: M = 0.38, SD = 0) and (3) dependency to their mothers (OACC: M = 4.29, SD = 3; ICSI: M = 4.54, SD = 0), fathers (OACC: M = 2.82, SD = 1; ICSI: M = 2.69, SD = 2) or themselves (OACC: M = 0.53, SD = 0.5; ICSI: M = 0.85, SD = 0.5). Limitations, reasons for caution This study used multiple evaluators, which may induce a potential evaluators bias. The small sample size limits the validity of our findings to a whole population. As the study is still ongoing, the data to be presented will expand. Wider implications of the findings The findings are relevant to clinics offering anonymous oocyte donation, to (future) parents who used or who considerate using anonymous oocyte donation to create a family. Trial registration number not applicable