The first live birth after an IVF frozen embryo transfer was in 1983. Since then, there have been hundreds and thousands of babies born the world over with frozen embryos. A third of the babies born today with IVF are with frozen embryos. At InVia Fertility Specialists, currently, in about 40% of IVF cycles the embryos are frozen and transferred in a subsequent cycle.
It is therefore reasonable to ask, “How are frozen embryo babies doing?” “Are they healthy?” “How do they compare with babies conceived with fresh embryo transfer?”
Lower risk of bleeding during pregnancy (antepartum hemorrhage)
Lower risk of preterm birth (before 37 weeks of pregnancy)
Bigger babies (by an average of 253 gm in another report)
Less risk of fetal death
The incidence of tubal pregnancy is lower with frozen embryo transfer when compared to fresh embryos.
What is the explanation for this improvement in outcome?
A definite reason for this is not known.
Various theories, however, have been proposed.
IVF subjects women to unusual hormone levels to stimulate egg release. That hormonal change can make the womb a "less hospitable place" for an embryo to implant. When frozen embryos are used, enough time has passed for the woman's hormonal levels to return to normal and this may allow embryos to implant more successfully, forming a well-functioning placenta which nourishes the embryo.
The physical effects of freezing and thawing embryos may filter out weaker embryos and allow only good quality ones to survive, resulting in better fetal growth.
These data are reassuring, and for that reason, patients are encouraged to freeze their (excess) embryos. Freezing embryos enables couples to have several cycles of IVF with eggs collected during one round of treatment. By putting some on ice, couples can use up their fresh embryos before moving on to frozen ones at a later date.
These also data suggest that babies born from frozen embryos have a significantly longer gestation period and are significantly heavier at birth compared to babies from fresh embryos. This is important because prematurity and low birth weight are both risk factors for poorer health later in life and are linked to higher rates of behavioral and learning difficulties.
Should all embryos be frozen and transferred in a subsequent cycle?
The jury is out on this one. There are only a small percentage of programs that are currently freezing all embryos. However, this may change as freezing techniques improve and if we routinely start screening embryos for chromosomal abnormalities (pre-implantation genetic screening (PGS) or SMART IVF).
At InVia Fertility Specialists, we have a very successful frozen embryo transfer program. Currently, our live birth rate in young patients with the transfer of a single chromosomally normal embryo (SMART IVF) is around 70%!
Dr. Karande is Board Certified in the specialty of Obstetrics and Gynecology as well as the subspecialty of Reproductive Endocrinology and Infertility. He is a Fellow of the American College of Obstetricians and Gynecologists and Member of the American Society for Reproductive Medicine.