In a fresh IVF cycle, eggs are retrieved and placed, along with sperm, in a special culture medium that encourages fertilization and growth of the embryos.
The entire IVF cycle takes about one month from the time a woman begins taking hormones to stimulate egg production to the time she is tested to determine if she is pregnant. This cycle is often preceded by a month on birth control pills.
Fresh IVF Cycle Process
The in vitro fertilization cycle consists of four stages: stimulation, egg retrieval, fertilization and transfer.
Stimulation - Frequent ultrasound exams are performed to evaluate the growth of the follicles that will produce the eggs. Hormonal monitoring with blood tests may also be used. Adjustments will be made to the stimulation medication doses based on these findings.
Egg retrieval - When the follicles and the eggs within them are judged to be mature, the eggs are retrieved by needle aspiration. During this procedure, a physician uses ultrasound to guide a needle through the vagina and into the ovaries to collect eggs. An anesthesiologist is present to provide pain medication and sedation so the patient does not feel pain. All follicles are aspirated to maximize the number of eggs collected.
Fertilization - Once the eggs have been collected, the male provides a semen sample. Sperm and eggs can be joined in one of two ways. They can be mixed in a laboratory dish or a single sperm can be injected into each egg, a process called intracytoplasmic sperm injection, or ICSI.
The following day, eggs are examined to check for fertilization. Fertilized eggs become embryos. Typically, about 75 percent to 80 percent of the eggs become fertilized.
Embryo Transfer - Three to five days after fertilization, embryos will be selected and transferred to the woman’s uterus.
About 10 days later - two weeks after the egg retrieval – a blood test is performed to check for pregnancy. If the results are positive, the test is usually repeated 48 hours later to check that the pregnancy is progressing. If these results are also good, an ultrasound is planned for around seven weeks of gestational age (about five weeks from egg retrieval) to assess the location and number of pregnancies.
In vitro fertilization patients commit to taking several medications to help improve the likelihood of pregnancy.
A woman receives various stimulation hormones to encourage the growth of follicles, as well as a medication to prevent premature ovulation. Once the follicles are mature, another medication triggers the final maturation of the eggs prior to retrieval.
Progesterone, a female hormone that prepares the uterus to receive and sustain an embryo, is given after egg retrieval and is continued until 10 weeks of pregnancy (eight weeks after retrieval). A woman then continues prenatal care with her obstetrician.
A few days (six to seven) after fertilization, the thin shell surrounding the embryo—the zona pellucida—should erupt. This “hatching” occurs to allow the embryo’s cells to come in contact with the uterus, allowing implantation – and pregnancy. Without hatching, implantation cannot take place.
In some women, the zona becomes toughened, preventing the embryo from hatching. Therefore, “assisted hatching” may be necessary in certain IVF procedures. Three days after egg retrieval, eggs are viewed under high magnification and a small hole is mechanically made in the zona. Specialists at the Reproductive Medicine Center typically recommend hatching for women who have repeated implantation failures, older women and situations where the embryologist notes a thickened zona.
Frozen Embryos (Cryopreservation)
Any embryos remaining following a fresh IVF cycle (those not placed in the uterus) can be frozen through a special technique of cryopreservation and used in the future if the first cycle does not succeed. They can also be used years later for another pregnancy if desired by the couple.
The process does not require ovarian stimulation. Rather, the woman takes oral estrogen in increasing doses followed by progesterone to prepare the uterus for implantation. At the right time, embryos are thawed and placed in the uterine cavity.