The demand for treatments requiring oocyte donation has increased significantly due to delayed motherhood. According to data from the European Society of Human Reproduction and Embryology (ESHRE), Spain performs the highest number of such treatments in Europe.

Many IVF clinics offer couples seeking fertility treatment the possibility of undergoing expanded carrier screening to mitigate the risk of passing on certain recessively inherited genetic diseases to their offspring. Under this inheritance pattern, a person develops the disease only if they inherit two altered copies of the gene – one from each parent – who are usually healthy carriers. Expanded carrier screening is also used in egg or sperm donation cycles to ensure a compatible donor is assigned and reduce the risk of offspring being affected by the screened conditions.

Although reports of children born with genetic disorders inherited from gamete donors are rare in the scientific literature, there remains a residual risk despite rigorous donor selection. For this reason, a team of researchers at Dexeus Mujer, led by Dr Gabriela Palacios, of the Genetic Counselling Unit , conducted a large retrospective study to assess the impact of these tests on reducing adverse outcomes in babies born through oocyte donation. These findings are crucial for providing appropriate counselling to patients and for supporting the inclusion of carrier tests in gamete donation cycles – for both donors and recipients of oocytes or sperm.

The study analysed adverse outcomes in a total of 4,565 egg donation cycles, classified as either ‘low risk’ or ‘high risk’. Researchers identified the number of high-risk pairings – defined as carriers of the same autosomal recessive condition – following expanded carrier screening of the egg donor and the recipient’s male partner (or sperm donor, in dual donation cycles).

A total of 67 recipients (1.47%) reported an adverse obstetric or neonatal outcome. A genetic cause was confirmed in 25 of these cases (37.3%). The remaining 42 cases (62.7%) included congenital malformations, neurodevelopmental disorders, and other conditions of presumed genetic origin. Furthermore, 211 high-risk pairings were identified (4.6%, 211/4,565), equating to an estimated risk of 1.15% for affected offspring. In addition, 52 egg donor candidates (2.8%, 52/1,875) were found to be carriers of X-linked conditions – corresponding to an estimated 0.7% risk of affected offspring – and, therefore, were excluded from the oocyte donation programme.

The authors concluded that the implementation of expanded carrier screening led to a 55.7% reduction in the risk of adverse outcomes, from a potential rate of 3.32% down to 1.47%. Nonetheless, some adverse outcomes remain unavoidable.