PRAGUE — Single embryo transfer does not lower success rates compared to double embryo transfer in most patients who need preimplantation genetic diagnosis, according to a study presented at the annual meeting of the European Society of Human Reproduction and Embryology.
However, one subset of patients needing preimplantation genetic diagnosis (PGD)—those with translocations—may need more than one embryo transferred to achieve adequate pregnancy and delivery rates, reported Dr. Patricio Donoso of University Hospital, Dutch-speaking Free University Brussels, Belgium.
It has been suggested that patients undergoing PGD may have a smaller chance of getting pregnant after in vitro fertilization (IVF) than do patients who do not undergo PGD, Dr. Donoso said in an interview. Although there is still some debate about whether the PGD biopsy is slightly harmful to the embryo, the main reason for concern is that PGD often identifies many embryos as unsuitable for transfer. “In regular IVF, we usually select the most morphologically normal-looking embryo for transfer. In PGD patients, the healthy embryo is not necessarily the one with the best morphology, so that makes embryo selection more difficult,” he said.
His retrospective study of PGD patients was performed both before and after a Belgian law mandated single embryo transfer (SET) in all women under 36 years of age undergoing their first trial of IVF. The study included 50 PGD patients who received double embryo transfer (DET) between 2002 and 2003 (before the law was implemented) and 55 PGD patients who received SET after implementation of the law in July 2004.
Most patients had experienced recurrent miscarriage, and indications for PGD included monogenic disorders, such as myotonic dystrophy and cystic fibrosis, and translocations.
The study found no statistical difference in delivery rates between the DET and SET groups overall (32% vs. 25.5%); the rate of multiple pregnancies was significantly different—31% in the DET group and none in the SET group.
However, in the subgroup of patients with translocations, among those who received only one embryo there was a reduced delivery rate compared to those who received DET (18% vs. 40%). Although this trend did not reach statistical significance, Dr. Donoso said he expects it will with the addition of more patients. “If this trend continues, maybe we will have to discuss transferring more than one embryo in these patients, which would mean changing the law in Belgium,” said Dr. Donoso.
However, he said collecting a big enough series to explore this trend will be very difficult, because it is not a frequently occurring pathology.