How an IVF cycle works
In vitro fertilization and embryo transfer or conventional IVF, is a complex process containing many small steps. At Infertility Solutions, each couple meets with one of our nurses to individually review the details of that process and review an individual schedule to help you through the many details.
We work with patients in groups. We do this because it enables us to be more focused on the details we need to address. Most of those details relate to the IVF laboratory. The laboratory is one of the major determinants of success with IVF. We pick approximately one week each month during which we perform the laboratory part of IVF. This enables us to fine tune the laboratory with quality control checks for the rest of the month. This limits our need to maintain, adjust, repair or clean any equipment while patient materials are using the laboratory.
For many of our patients, the first step is to synchronize their menstrual cycle with the lab. For most patients we do this initially by placing them on birth control pills. Birth control pills are not strictly necessary, but enable our patients to be on medications given by injections for the shortest period of time as well as provide some minor endocrine benefits for the cycle.
Patients then often go on the medication lupron to down-regulate their pituitary hormone production. This prevents their pituitary from producing hormones that could damage the eggs. Lupron is a minor modification of a 10 amino acid neurotransmitter, GnRH, naturally produced by the brain. Lupron belongs to a class of medications called GnRH agonists. There are more recently developed medications that have a similar effect and belong to the class of GnRH antagonists (usually ganirelix). We use them as an alternative in about half of our patients. Some medications appear to work better in some patients than in others and thus it is good to have alternative approaches. If a patient fails to get pregnant with one approach, we usually vary our approach in the next cycle.
After oral contraceptive have stopped and a patient's period has started, the main medications can begin to be used. We use a number of different combinations, but the key feature is that the main medications contain FSH, which is the hormone that causes follicles in the ovary to develop and mature. Patients are usually on these medications for 10 to 14 days. During that time we will be measuring estradiol and progesterone levels, evaluating the ovaries with ultrasound examinations, and adjusting the medications that are given.
When the ultrasound and hormonal parameters seem optimal for that patient, she will take hCG. This will cause the eggs to mature (discarding half of their chromosomes into a polar body) and become free floating within the follicle. Enzymes begin to break down the follicle wall and will release the egg into the abdomen in about 38 hours. The egg aspiration procedure is scheduled for 36-38 hours after HCG is taken.
The eggs are taken out in our procedure room. A nurse anesthetist starts an IV through which she will give medications so that the patient does not feel the procedure. (We use an independent group of nurse anesthetists who specializes in providing office anesthesia.) The follicles are visualized transvaginally by ultrasound. A needle is passed through the vagina into each follicle. The fluid in the follicle is aspirated and then passed to the embryologist. The embryologist then tries to find the microscopic egg in this follicular fluid. Great care is taken to maintain the egg in an environment that is stable and optimally meets its nutritional needs. Initially the primary concerns involve temperature, pH and air quality in the room and lab. This concern expands to include everything that comes in contact with the egg/embryo including the gases around the embryo (see reduced oxygen tension), media constituents related to the embryo's state of development, and the stability of those environments.
The eggs start to be fertilized about 3 to 6 hours after they are obtained. This either involves inseminating the eggs with her partner's sperm, which has been specially prepared, or injecting a single sperm into each of the eggs (ICSI). If ICSI is done, the granulosa cells that layer the egg are enzymatically cleaned off so that the interior of the egg can be visualized and the egg handled more easily. If ICSI is not performed, the sperm will do much of this cleaning overnight. About five percent of patients with normal sperm will unexpectedly have no fertilizations with IVF. We often split the eggs on a first cycle and perform ICSI on some of them to decrease the likelihood of there being no fertilizations.
The eggs are examined for fertilization in the morning. The number of fertilizations as well as egg and embryo quality will be used to formulate a plan to transfer the embryos back to the patient after 2, 3, 5, or 6 days of incubation. Most of our patients have their embryos transferred on day 3. About one-fourth of patients have their transfer on day 5 (blastocyst).
The number of embryos to be transferred depends on their quality (cell number and normality of appearance), patient characteristics, and day of transfer. The number to be transferred is a joint decision balancing the wishes of the patient and the safety of the situation with respect to risk of multiple births. Most patients have two or three embryos transferred. Single embryo transfer is always an option if the patient produces good quality embryos. For patients under thirty-five with excellent quality embryos, national recommendations are to transfer a single embryo. It is not possible to make a fully rational decision on the number of embryos to transfer until one has information on the quality of those embryos. Patients should have an understanding of the general issues involved prior to starting IVF. Usually objectives will be formulated on the day of aspiration. On the day of transfer, the physician will share the physician and embryologist's assessment of the patient's embryos and the couple together with the physician, will then decide on the number of embryos to transfer.
On the day of transfer, assisted hatching is performed if indicated, and the transfer is performed using ultrasound guidance. The transfer is performed on a patient with a full bladder utilizing medications to relax the uterus. The objective is to make the transfer be as gentle for the embryos as possible. Assisted hatching involves making a microscopic hole in the shell around the egg to help the embryo hatch which is necessary prior to implantation.
On the day of transfer, patients will also decide on the disposition of their remaining embryos. Embryos that have stopped growing no longer have the potential to become babies and are discarded. Couples will have to decide whether or not to continue culturing their remaining embryos and cryopreserve those at the blastocyst stage (day 5 and 6) that appear to have good potential to become pregnancies.
We use a number of different medical regimens to enhance and support implantation. These approaches have evolved over time based on medical publications. The regimens always include progesterone in some form.
Pregnancy tests are done in about two weeks. A positive pregnancy test is just the first step. Ultrasound is used to determine growth in the uterus, embryo number, and eventually embryo viability. If a heartbeat is seen as early as 6 weeks (3 weeks after the aspiration), there is about a 90% chance of a delivery.