The big difference between an IVF cycle and a regular menstrual cycle is that ovulation does not take place in an IVF cycle. Instead, the eggs are retrieved at the point of maturation and are fertilized in the IVF lab. Embryos are then transferred to the uterus to initiate pregnancy. Once the embryos are transferred back into the uterus, there is nothing distinguishable between embryos fertilized in the body or in an IVF laboratory.
Below is a more detailed description of the IVF process. It is important to remember that IVF is a step-by-step process and one step cannot begin until the previous step has been completed.
The first few days of a menstrual cycle is considered a “baseline.” If all baseline parameters are met, this is considered the starting point of an IVF cycle. Rather than waiting for the onset of your next period and starting then, the baseline state is often induced by a combination of drugs such as birth control pills and/or Lupron. This produces a more predictable response and enables us to manipulate hormone levels more effectively.
Everyone who undergoes IVF will take at least one of the suppression drugs (Lupron, microdose Lupron, Synarel, Antagon, or Cetrotide). Suppression drugs not only help bring about the beginning, or baseline stage, they also prevent you from ovulating on your own once the stimulation phase begins. In an IVF cycle, it is important that you do not ovulate for two reasons: First, if the eggs leave the ovary, the doctor will not be able to retrieve them. Second, if you do ovulate, there will likely be multiple eggs exposed to sperm in the fallopian tube, therefore putting you at risk for a high-order multiple-gestation if you have sexual intercourse.
It is very important to have a proper baseline. The parameters for a proper baseline evaluation are as follows:
- Neither ovary has any large cysts.
- Hormone levels of estrogen (e2), progesterone, LH are all low.
- Uterine lining is thin, all sloughed off, and ready to begin anew.
If there is a cyst on the ovary, elevated hormone levels or a thickened endometrium, IVF treatment may be less successful and therefore should not begin. For this reason, one of the first types of medication you will take is a suppression drug, which acts to induce a period and keep your cycle from progressing towards ovulation. You may experience menopausal-like symptoms on the suppression drugs, such as headaches or hot flashes. This is due to the estrogen levels being suppressed by the medication. To maximize the chances of a proper baseline starting point, patients are often asked to take birth control pills in the preceding menstrual cycle and may overlap the birth control pill and a suppression medication.
Progressing Toward Egg Retrieval
To encourage growth of multiple follicles on both ovaries, injectable gonadotropin medications are used to stimulate the ovaries to produce more follicles than would be produced in a normal menstrual cycle. Gonadotropins, often referred to as “FSH” or “stimulation drugs” ( Gonal-F, Repronex, Menopur, Follistim, Bravelle and others), are given to help ovaries to develop multiple follicles over 7-14 days.
During this time, our team of doctors, nurses and sonographers will monitor your response to these medications by using ultrasound pictures and hormone testing. The doctors evaluate the size and quantity of the follicles on your ovaries as well as your estrogen level to determine the most appropriate dose of medications. During IVF treatment, a typical estrogen level will be less than 50 at the time of baseline evaluation and may get as high as 2,000 - 4,000 (In a normal menstrual cycle the estrogen level starts out less than 50 and peaks at about 250-350.).
Once most of the follicles are in the mature range (16-22mm) your doctor will decide when to discontinue stimulation drugs and plan the egg retrieval. For a normal menstrual cycle, the first half of the cycle ends with ovulation. In an IVF cycle, it ends with an egg retrieval.
The medication used to simulate an LH surge is hCG. You may recall that this is the hormone of pregnancy. The hCG will cause the final maturation of the eggs and loosen them from the inside of the follicle walls, much the same way as an LH surge functions in a natural menstrual cycle. It will also cause you to ovulate in 36 hours. For this reason, we prescribe a precise time for you to take the hCG and we schedule your egg retrieval 35 hours later. This gives you the maximum benefit of the hCG while stopping just prior to ovulation.
It may be helpful to think of egg retrieval as assisted ovulation. During the egg retrieval you are sedated and sleeping comfortably while the doctor withdraws the fluid contents of each follicle, using an ultrasound-guided needle. The fluid is passed in a syringe to the embryologist, who then examines the liquid to see if an egg is present. By the time you leave the clinic that day, you will know how many eggs were retrieved.
The next day you will know how many of the eggs fertilized into embryos. In the days that follow we will monitor those embryos to see if they continue to divide and grow. It is important to remember that a follicle is not the same as an egg. When you are monitored during your IVF cycle, we use ultrasound technology to measure and count how many follicles are in the ovary; however, we cannot see the eggs inside.
Although we hope that each follicle contains an egg, we know that this is not the case. Not every follicle has an egg, not every egg is alive, not every live egg is mature, not every mature egg fertilizes and not every fertilized egg (embryo) continues to cleave until the day of embryo transfer.
Typically, three to five days after egg retrieval, embryos are put back into the uterus in a procedure called embryo transfer. This procedure feels similar to a PAP smear exam. It is not painful; therefore, patients usually are not sedated. The final decision regarding how many embryos to transfer and what to do with the remaining embryos is made on the day of transfer. The decision is made collaboratively among you, your partner, the doctor, and the embryologist.
Day 3 Transfer Vs. Day 5 (Blastocyst) Transfer
In many IVF cycles, the doctor may recommend a day 5 or “blastocyst” transfer. If the embryo(s) survives in the IVF lab for five days after the egg retrieval, it is likely that it will have reached the blastocyst stage. At this stage we are able to transfer just two embryos to achieve the same pregnancy rate as transferring three embryos on day 3. This all but eliminates the instances of triplets. Twin pregnancies, however, are more likely with a blastocyst transfer. Also, some data suggest that pregnancy rates are slightly higher with blastocyst transfers.
The drawback to having a transfer on day 5 is that not all embryos survive that long. The possibility of having nothing to transfer is much greater when planning a day 5 transfer. The embryos that do not survive to day 5 in the lab probably would not have created a pregnancy had they been transferred on day 3, but there is no way to know this for certain. Although the decision about how to proceed cannot be finalized until we know how many embryos we have to work with, the discussion about your preferences and the doctor’s recommendation in your specific case should be made well in advance.
At GIVF, our general guideline for deciding day 3 vs. day 5 is that you should have at least 5 or 6 embryos on the day after egg retrieval to consider a day 5 transfer. You may decide to draw the line higher or lower than this. This is a discussion that should take place well before the egg retrieval, so that you have time to thoroughly weigh the pros and cons, discuss it with your partner and your doctor, and even do research on your own if you like.
Fourteen days after egg retrieval, a blood test is performed to determine if a pregnancy resulted from this process. If the test is positive, we will monitor the level over the following days/weeks to confirm things are progressing as they should. If the pregnancy test is positive, you may have your blood tested one, two, three, or more times. Most women are not symptomatic of pregnancy this early, so don’t be alarmed if you don’t “feel” pregnant, even if you’ve been pregnant before. Spotting (sometimes even heavy bleeding) can occur even if you are pregnant.
Please remember that the progesterone medication you are taking is vital to the pregnancy and should not be stopped or interrupted unless you are specifically told to do so by a doctor or a nurse.
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