Stages of an assisted conception cycle
Stages of an assisted conception cycle
Step 1: Ovarian Stimulation
The first phase of an assisted reproduction cycle is ovarian stimulation. Since every woman ovulates a single follicle every month, stimulation induces several follicles to mature at the same time in a selected menstrual cycle, resulting in a number of eggs that can be collected and used for an IVF treatment.
Several medications can be used for this “superovulation” to occur and the choice of drug, dosage and protocol is evaluated on a case to case basis as it is dependent upon the age, ovulatory characteristics, and the history of any previous cycles of the patient.
Step 2: Follicle Development Monitoring
During stimulation, the ovarian response to the medication is monitored, with ultrasound scans and a dosage of plasma estradiol. Monitoring the development of the follicles is important because the cycle may need to be suspended if there is not an adequate number of follicles maturing or if the response to stimulation is excessive.
When the response to the ovarian stimulation is considered adequate, HCG is administered. This is a substance that induces the final maturation of the oocyte, making it available for fertilization. At this stage, the follicles reach an average diameter of over 18 mm and have good functional activity.
Step 3: Egg Retrieval
Egg retrieval begins 34-36 hours after the administration of HCG, irrespective of the IVF method used. The oocytes are extracted transvaginally, with ultrasound guidance. This surgical procedure, although minor, is performed under anesthesia to avoid discomfort and pain.
During the retrieval, antibiotics are administered to prevent infections that commonly result from surgery, and in certain cases human albumen may be administered to avoid OHSS. All follicles that matured are aspirated including any ovarian cysts that may have formed during stimulation.
The day the eggs are collected is “Day 0”.
In 0.5% of the cases, there may be no eggs that can be collected, or the eggs retrieved are unsuitable for fertilization because they are either immature or over mature.
Step 4: Sperm Collection
Sperm is normally collected the same day as the egg retrieval but can also be collected before and frozen. Masturbation is the most frequent method used to produce a sperm sample, however, sperm can also be obtain from men who are unable to ejaculate or have no sperm in their semen through a minor surgical procedure.
If donor sperm is being used, it is thawed on the same day as the egg retrieval procedure.
Step 5: Laboratory Techniques
After the eggs are retrieved, they are transferred to the embryology laboratory where they are placed in culture in special incubators that maintain conditions suitable for their survival. After a few hours the eggs are then inseminated with either a fresh or frozen sample of sperm.
Insemination may occur through either conventional IVF-ET by which 2 to 3 thousand mobile spermatozoa are brought into contact with each oocyte in a petri dish or through an ICSI technique by which one sperm cell is injected directly into the oocyte. The choice of insemination method used depends primarily on the quality of the seminal fluid (number, motility and morphology of the spermatozoa), but may also depend on other factors.
The percentage of fertilization is 75% with both methods however, once it has been obtained, the probability of embryonic development is high but not certain.
Step 6: Embryo Transfer
The embryos may be transferred between Day+2 and Day+5, during different stages of development.
The intrauterine transfer method is generally simple and painless. It does not require any form of anesthesia or sedation, and consists of introducing a very fine catheter through the cervical channel into the uterine cavity. This is a delicate maneuver because the embryos and the endometrium (mucous membrane that lines the uterine cavity) must not be stressed in any way.
Step 7: Pregnancy Test
A pregnancy test is taken after two weeks have passed following the embryo transfer. Although usual activities may be resumed during this 14 day waiting period, it is advisable not to do anything physically demanding or extremely tiring. It is also important to keep in contact with your gynecologist in case vaginal spotting or bleeding occurs.