The placement of the embryo into the uterus, usually referred to as ‘embryo transfer’, is a fairly simple procedure, medically speaking. For most couples who desire to have children, however, it’s a very special moment of the fertility treatment. We know better than most how fragile embryos are, as they are the start of a new life. During the treatment, we take the greatest care with the embryos.
After the oocytes are taken from the ovaries (oocyte retrieval), they’re fertilized in our laboratory via an in vitro fertilization (IVF) or an intracytoplasmic sperm injection (ICSI). After that, they’ll go into an incubator and start to divide.
Day 1: Pre-nucleus stage
Day 2: Two-to-four-cell stage
Day 3: Eight-cell stage
Day 4: Morula stage
Day 5: Blastocyst stage
The embryo transfer will take place on the fifth day after the oocyte retrieval, when the embryos are in the blastocyst stage. Embryos will be frozen when they develop until the blastocyst stage.
The embryo transfer itself will only take a few minutes. It’s a routine procedure that can be done without anesthetic. After discussing it with the future parents, the physician will place one or multiple embryos in the uterus, complying with current legislation. The physician will use a speculum to bring the cervix into view, after which a soft synthetic catheter is inserted into the uterus. The exact location of the embryo(s) placement is determined using an ultrasound. At this point in time, the embryo is still hardly visible to the naked eye and is contained in a very small droplet. This will be inserted painlessly into the uterus through the catheter.
As soon as the embryo is inside the uterus, it’ll be able to lodge in the endometrium and develop further from there. The patient is allowed to go home immediately following the procedure.
There are no special rules applying to your day-to-day behaviour after an embryo transfer. The best thing is for the patient to resume her usual activities. We used to prescribe several hours or even days of bed rest to women after an embryo transfer. However, according to recent data, bed rest does not have a positive effect on the success ratio and may even be negative, as extended immobilization increases the risk of thrombosis.
We do advise patients to follow the same guidelines as pregnant women would, such as dietary advice, no smoking and no alcohol or other harmful substances.
The quality of the embryo and its development after being transferred to the uterus do have an influence on the chance that the treatments will be successful. After the embryo has been transferred, the prospective parents barely have an influence on whether the attempt will succeed or not. Two weeks after the embryo transfer, you’ll be able to use a pregnancy test to see whether the embryo successfully lodged in the uterus.
An embryo transfer in and of itself isn’t associated with any inherent risks. According to Dutch legislation, we can’t transfer more than one embryo during the first two treatments of women younger than 38. If a patient is 38 years old or older, or it’s her third treatment, we can transfer two embryos.
If the embryo transfer is successful, the hormone hCG (produced during pregnancy) may cause a phenomenon called overstimulation syndrome. This will usually only occur after an oocyte retrieval, and only if hormonal stimulation caused many follicles to mature at once. Overstimulation syndrome may cause swelling of the ovaries and fluid retention in the abdominal and chest cavities. The worst cases may require hospitalization. If you are at a higher risk of developing overstimulation syndrome, you will be informed by the team treating you.
On the day of the embryo transfer, the highest-quality embryo is transferred into the uterus. If there are several high-quality embryos, the remaining embryos will be incubated in our laboratory. After five to six days, when they’ve reached the blastocyst stage, they will be entered into cryogenic storage (frozen).
If the treatment doesn’t result in a pregnancy, one of these embryos can be thawed and transferred into the uterus at the right time in your menstrual cycle, so that you won’t have to undergo another hormonal stimulation and oocyte retrieval.