If you have tested abnormal embryos, you might wonder what would happen if you were to transfer one. Some people produce few or no normal embryos, especially with age, and it can be heartbreaking to discard and end up with nothing to transfer.
Many clinics will refuse to transfer aneuploid embryos. Some may even refuse to transfer mosaic embryos.
There have, however, been studies that show live births after the transfer of aneuploid embryos. Here we will look at 3 of them.
Study 1: 2 live births
This 2021 study looked at 32 cycles consisting of the transfer of 77 mosaic or aneuploid embryos. There were 9 pregnancies and 5 live births, including 2 live births from aneuploid embryos.
The 2 aneuploid embryos which became live babies were a 5AA, 46, XY del (15) (q24.1-qter) tested by NGS and a 5BC, 45, XY, -22, tested by comparative genomic hybridization test. Both were part of a double embryo transfer with another abnormal embryo.
They also grew embryos in the lab and found that on day 3 every embryo was more than 50% aneuploid and this decreased with time. From an 83.33% aneuploidy rate at day 3 to 11.1% on day 4 and following day 6 there were no embryos with 100% aneuploid cells.
Study 2: 68 ongoing pregnancies or delivered
This 2019 study involved a worldwide survey of clinics in which they asked about transfers of aneuploid embryos.
There were 135 transfer cycles of abnormal embryos resulting in 68 ongoing pregnancies or deliveries, including 35 live births at the time of survey.
Study 3: 9 babies tested normal in the womb
This 2018 study described 9 cases of aneuploid embryo transfer.
6 cases of single embryo transfer (including one mosaic), one was terminated before testing but the other 5 all tested normal either by cell free fetal DNA (cffDNA) or amniocentesis.
3 were double embryo transfers, 1 resulted in a singleton which tested normal, one resulted in twins which tested normal (although one embryo was classified as no results), and the final double embryo transfer (which was actually of a normal embryo and an aneuploid) resulted in triplets but was reduced to one tested normal singleton. The reduction of the twins took place because an omphalocele and thickened nuchal fold was detected for one twin.
So there were a total of 9 fetuses tested normal but one may have originated from the euploid embryo, one originated from the no results embryo, and one was mosaic, bringing it to a total of 6 healthy fetuses from tested aneuploid embryos.
The abnormal embryos which resulted in tested normal fetuses previously tested:
- Trisomy 7
- Monosomy 1 and monosomy 7
- Trisomy 22 or Partial monosomy 1pter-p36.12 (double embryo transfer which resulted in singleton pregnancy)
- Monosomy 2
- Trisomy 18
- Monosomy 5
Counterpoint: 102 transferred for 0 sustained pregnancies
Here I have shown research proving that sometimes tested aneuploid embryos do self-correct in the womb to result in healthy babies.
We can, of course, also find studies which show more negative results.
In this 2020 study 402 embryos were biopsied but not tested until after transfer. Instead, the best embryo was chosen based on morphology. This resulted in the transfer of 102 embryos that were later tested aneuploid and there were 0 cases of ongoing pregnancy or live births.
The positive side to this is that the transfer of aneuploid embryos also didn’t result in the birth of unhealthy babies.
Conclusion
Transferring abnormal embryos can result in live birth. The success rates are not as high as euploid embryos and there is a higher rate of miscarriage. The evidence suggests they don’t usually result in giving birth to babies with abnormalities so the biggest risk in transferring is a miscarriage. This might be an acceptable risk if you only have abnormal embryos. Also, euploid embryos
References:
Yang, M., Rito, T., Metzger, J. et al. Depletion of aneuploid cells in human embryos and gastruloids. Nat Cell Biol 23, 314–321 (2021). (link)
Patrizio P, Shoham G, Shoham Z, Leong M, Barad DH, Gleicher N. Worldwide live births following the transfer of chromosomally “Abnormal” embryos after PGT/A: results of a worldwide web-based survey. J Assist Reprod Genet. 2019 Aug;36(8):1599-1607. doi: 10.1007/s10815-019-01510-0. Epub 2019 Jun 24. PMID: 31236830; PMCID: PMC6707985. (link)
Darilek, Sandra & Nassef, Salma & Huguenard, Sarah. (2018). 267: Pregnancy outcome following transfer of an aneuploid embryo. American Journal of Obstetrics and Gynecology. 218. S170. 10.1016/j.ajog.2017.10.196. (link)
Ashley W. Tiegs, Xin Tao, Yiping Zhan, Christine V. Whitehead, Emre Seli, George Patounakis, Jacqueline Gutmann, Arthur J. Castelbaum, Thomas Kim, Chaim Jalas, Richard Thomas Scott, A MULTI-CENTER, PROSPECTIVE, BLINDED, NON-SELECTION STUDY EVALUATING THE PREDICTIVE VALUE (PV) OF AN ANEUPLOID DIAGNOSIS WITH PGT-A AND THE IMPACT OF BIOPSY, Fertility and Sterility, Volume 114, Issue 3, Supplement, 2020, Page e30, ISSN 0015-0282, https://doi.org/10.1016/j.fertnstert.2020.08.111. (link)