Understanding IVF Embryo Development
Did you know your surrogate is already “pregnant” before an embryo transfer even happens? It can be hard to comprehend, but that it is the reality of IVF pregnancies.
In a traditional pregnancy, gestational age is determined based on the day of ovulation. Fertilization and implantation of the embryo typically occurs about two weeks later. In the case of IVF, and specifically gestational surrogacy, pregnancy works a bit differently. The eggs that will eventually become embryos are not allowed to travel from the ovary into the uterus to await fertilization. Instead, the eggs are retrieved, either from an intended mother or egg donor, directly from the ovary before they are released. This happens two weeks into a woman’s typical 28-day menstrual cycle.
Growth & Evaluation
Those eggs are then fertilized outside of the body and allowed to begin growing. A reproductive endocrinologist closely monitors the cell multiplication over the next several days. In the case of a planned fresh embryo transfer, the eggs will then be transferred into an awaiting uterus on either day 3, 5, or 6 of external development. In the case of a planned frozen embryo transfer, the embryos are typically frozen, thawed and transferred on day 5 of development.
In the meantime, the recipient of the embryo will be on a hormone therapy regimen that will cause their body to mirror where it would be in a non medicated cycle. This process allows doctors to create the ideal environment for the embryos to implant and grow before moving forward with the transfer.
With this in mind, the embryo recipient walks into the fertility clinic on transfer day 2 weeks “pregnant” before the transfer even occurs. During the transfer, the doctor will migrate the embryo or embryos into the awaiting uterus, and at the conclusion of the transfer, the recipient is said to be 2 weeks plus the age of the embryo pregnant. If a 5-day blastocyst was transferred, the recipient will walk out of the clinic 2 weeks and 5 days pregnant.
The term “pregnant” is relative to whether the embryos actually implant and continue to develop. A pregnancy test, which will consist of a blood test, will generally be done 10-12 days after the embryo transfer. If the result of the pregnancy test is positive, your surrogate will be somewhere between 4 weeks 3 days-5 weeks pregnant. Around the 10 week mark, your surrogate will be released to the care of an obstetrician and the pregnancy will follow the course of a traditional pregnancy.