Never mind 150 half-siblings: Try ‘twinblings,’ inadvertent full siblings from different mothers
The reaction reminded me that I’d come across a paper earlier this summer in the journal Fertility and Sterility. The case report, by fertility doctors in the Bronx and Westchester, begins as follows (emphasis mine):
At our institution, all patients using donor gametes to achieve pregnancy meet with an on-site psychologist before undergoing treatment. During this meeting, the existence of half-siblings based on anonymous gamete donation is discussed. Currently, the possibility of genetic full siblings, ‘‘twiblings,’’ as coined by Melanie Thernstrom, is not discussed, because the likelihood of such an occurrence is minute. We report herein such an occurrence at our institution.
The two women in the study were
…independently undergoing donor recipient cycles with anonymous donor oocytes and donor sperm.
The abstract continues:
Both women received oocytes from the same donor several months apart and then by coincidence selected the same anonymous sperm donor to create anonymous full-sibling embryos.
Both women conceived using the same donor sperm and donor oocytes in independent cycles, resulting in simultaneous pregnancy of full siblings.
So how was this discovered? And when?
Both patients underwent their respective donor-recipient cycles without complication and each conceived twin gestations several months apart from each other. On routine review of recently completed cycles in our database, it was noted by our lab director that these donor-recipient cycles used the exact same oocyte donor and the exact same sperm donor. At the time that this realization occurred, patient #1 was at 23 weeks’ gestational age with an ongoing pregnancy and supernumerary frozen embryos. Patient #2 suffered a spontaneous miscarriage at 9 weeks’ gestational age, but has frozen embryos for a potential future cycle.
In other words, the lab director discovered the parentage issues only after the pregnancies had begun, but nature averted the interesting ethical questions — for now.
The authors don’t speculate as to how often this sort of thing is likely to happen. They shared the news with an ethics committee at one of their institutions. After all, what if the siblings met and didn’t know they were siblings?
The majority of the committee thought that if both recipients were aware of the possibility of anonymous half-siblings before using donor gametes, that the providing physicians have no obligation to provide any further information to the recipients. The case was also presented to a group of regional mental health professionals specializing in infertility, who reached the same conclusion.
Still, the authors conclude:
As providers with the knowledge that anonymous full sibling embryos have been created, we may have an obligation to disclose this information to the patients.