In Vitro Fertilisation: To experience the joys of parenthood
In vitro fertilization (IVF) is a method of assisted reproduction that involves combining an egg with sperm in a laboratory dish. If the egg fertilizes and begins cell division, the resulting embryo is transferred into the woman’s uterus where it will hopefully implant in the uterine lining and further develop. IVF bypasses the fallopian tubes and is usually the treatment choice for women who have badly damaged or absent tubes.
For traditional conception to occur, the man must ejaculate his semen, the fluid containing the sperm, into the woman’s vagina around the time of ovulation, when her ovary releases an egg.
Following ovulation, the egg is picked up by one of the fallopian tubes. Since fertilization usually takes place inside the fallopian tube, the man’s sperm must be capable of swimming through the vagina and cervical mucus, up the cervical canal into the uterus, and up into the fallopian tube, where it must penetrate the egg in order to fertilize it. The fertilized egg continues travelling to the uterus and implants in the uterine lining, where it continues to develop.
In Vitro Fertilization (IVF) / Intracytoplasmic Sperm Injection (ISCI)
There are many factors that can prevent the union of sperm and egg. Fortunately, assisted reproductive technologies such as IVF/ICSI can help. IVF/ICSI is a method of assisted reproduction in which a man’s sperm and a woman’s eggs are combined outside of the body in a laboratory dish. One or more fertilized eggs (embryos) may be transferred into the woman’s uterus, where they may implant in the uterine lining and develop.
Excess embryos may be cryopreserved (frozen) for future use. Initially, IVF was used to treat women with blocked, damaged, or absent fallopian tubes. Today, IVF is used to treat many causes of infertility, such as endometriosis and male factor, or when a couple’s infertility is unexplained. ICSI is used to treat male factor infertility i.e. husbands with low sperm count, low motility, zero count & abnormal sperms will benefit from ICSI.
The basic steps in an IVF treatment cycle are ovarian stimulation, egg retrieval, fertilization, embryo culture, and embryo transfer. These are discussed in the following sections.
During ovarian stimulation, also known as ovulation induction, medications or “fertility drugs,” are used to stimulate multiple eggs to grow in the ovaries rather than the single egg that normally develops each month (Table 1). Multiple eggs are stimulated because some eggs will not fertilize or develop normally after fertilization.
|Medications for Ovarian Stimulation||• human menopausal gonadotropin (hMG)
• follicle stimulating hormone (FSH)
• luteinizing hormone (LH) (used in conjunction with FSH)
• human chorionic gonadotropin (hCG)
• clomiphene citrate
|Medications to Prevent Premature Ovulation||• Gonadatropin releasing hormone (GnRH) agonists
• GnRH antagonists
Clomiphene citrate is administered orally while the other medications listed are given by injection. These oral medications are less potent than injectable medications and are not as commonly used in ART cycles. There is no evidence that one injectable medication is superior to any other.
Timing is crucial in an IVF cycle. The ovaries are evaluated during treatment with vaginal ultrasound examinations to monitor the development of ovarian follicles.
Using ultrasound examinations and blood testing, the physician can determine when the follicles are ready for egg retrieval. Generally, eight to 14 days of stimulation is required. When the follicles are ready, hCG or other medications are given. The hCG replaces the woman’s natural LH surge and causes the final stage of egg maturation so the eggs are capable of being fertilized. The eggs are retrieved before ovulation occurs, usually 34 to 36 hours after the hCG injection is given.
Up to 20% of cycles may be cancelled prior to egg retrieval. IVF cycles may be cancelled for a variety of reasons, usually due to an inadequate number of follicles developing. Cancellation rates due to low response to the ovulation drugs increase with a woman’s age, especially after age 35.
When cycles are cancelled due to a poor response, alternate drug strategies may be helpful to promote a better response in a future attempt. Occasionally, a cycle may be cancelled to reduce the risk of ovarian hyperstimulation syndrome (OHSS). Treatment with a GnRH agonist or antagonist reduces the possibility of premature LH surges from the pituitary gland, and thereby reduces the risk of premature ovulation.
However, LH surges and ovulation occur prematurely in a small percentage of ART cycles despite the use of these drugs. When this occurs, since it is unknown when the LH surges began and eggs will mature, the cycle is usually cancelled. Collection of eggs from the peritoneal cavity after ovulation is not efficient.
Egg retrieval is usually accomplished by transvaginal ultrasound aspiration, a minor surgical procedure that can be performed under short general anesthesia. Some form of pain medication is generally administered. An ultrasound probe is inserted into the vagina to identify the follicles, and a needle is guided through the vagina and into the follicles. The eggs are aspirated (removed) from the follicles through the needle connected to a suction device.
Removal of multiple eggs can usually be completed in 15-20 mins. Some women experience cramping on the day of the retrieval, but this sensation usually subsides by the next day. Feelings of fullness and/or pressure may last for several weeks following the procedure because the ovaries remain enlarged. In some circumstances, one or both ovaries may not be accessible by transvaginal ultrasound. Laparoscopy may then be used to retrieve the eggs using a small telescope placed in the umbilicus especially patients with cancer.
Fertilization and embryo culture
After the eggs are retrieved, they are examined in the laboratory for maturity and quality. Mature eggs are placed in an IVF culture medium and transferred to an incubator to await fertilization by the sperm.
Sperm is separated from semen usually obtained by masturbation or in a special condom used during intercourse. Alternatively, sperm may be obtained from the testicle, epididymis, or vas deferens from men whose semen is void of sperm either due to an obstruction or lack of production.
IVF – Fertilization may be accomplished by insemination, where motile sperm are placed together with the oocytes and incubated overnight. ICSI in intracytoplasmic sperm injection (ICSI), where a single sperm is directly injected into each mature egg using a machine called the micromanipulator. ICSI is usually performed when there is a likelihood of reduced fertilization, e.g., poor semen quality, history of failed fertilization in a prior IVF cycle. In the United States, ICSI is performed in approximately 60% of ART cycles. Overall, pregnancy and delivery rates with ICSI are similar to the rates seen with traditional IVF. Genetic counseling is advisable before ICSI if inherited abnormalities are identified that may be passed from father to son.
IMSI (intracytoplasmic morphologically selected sperm injection) is a modified form of the ICSI (intracytoplasmic sperm injection) technique, however the only difference is that it carefully identifies the best quality sperm by magnifying 6000 times more than the conventional ICSI method.
Patients with severe oligoasthenoteratozoospermia (low sperm count) can benefit from IMSI. Where IMSI differs from ICSI, however, is that during IMSI, the embryologist carrying out the procedure uses an extremely high-powered microscope to select the sperm cells with the best morphological quality to be injected into the eggs. IMSI improves on the successes of ICSI men who have tried and failed to become fathers through at least two previous IVF/icsi attempts were twice as likely to succeed through IMSI than through another round of conventional fertility treatment.
Visualization of two pronuclei the following day confirms fertilization of the egg. One pronucleus is derived from the egg and one from the sperm. Usually 65% to 75% of mature eggs will fertilize after insemination or ICSI. Lower rates may occur if the sperm and/or egg quality are poor. Occasionally, fertilization does not occur at all, even if ICSI was used. Two days after the egg retrieval, the fertilized egg has divided to become a 2- to 4-cell embryo.
By the third day, a normally developing embryo will contain approximately 6 to 10 cells. By the fifth day, a fluid cavity forms in the embryo, and the placenta and fetal tissues begin to separate. An embryo at this stage is called a blastocyst. Embryos may be transferred to the uterus at any time between one and six days after the egg retrieval. If successful development continues in the uterus, the embryo hatches from the surrounding zona pellucida and implants into the lining of the uterus approximately 6 to 10 days after the egg retrieval.
Assisted hatching (AH) is a micromanipulation procedure in which a hole is made in the zona pellucida just prior to embryo transfer to facilitate hatching of the embryo. Although AH has not been demonstrated definitively to improve live birth rates, AH may be used for older women or couples who have had unsuccessful prior IVF attempts. There is no clear benefit of AH to improve pregnancy or live birth rates in other groups of IVF patients.
The next step in the IVF/ICSI process is the embryo transfer. No anesthesia is necessary, although some women may wish to have a mild sedative. The physician identifies the cervix using a vaginal speculum. One or more embryos suspended in a drop of culture medium are drawn into a transfer catheter, a long, thin sterile tube with a syringe on one end.
The physician gently guides the tip of the transfer catheter through the cervix and places the fluid containing the embryos into the uterine cavity. The procedure is usually painless, although some women experience mild cramping.
The number of embryos transferred is based on the patient’s age and other individual patient and embryo characteristics.
Extra embryos remaining after the embryo transfer may be cryopreserved (frozen) for future transfer.
Cryopreservation makes future ART cycles simpler, less expensive, and less invasive than the initial IVF cycle, since the woman does not require ovarian stimulation or egg retrieval. Once frozen, embryos may be stored for prolonged periods, and live births have been reported using embryos that have been frozen for almost 20 years. However, not all embryos survive the freezing and thawing process. There are two methods used to cryopreserve embryos: conventional (slow) freezing and “vitrification” or fast freezing. ART centers are cryopreserving oocytes (eggs) prior to fertilization.
This is done most commonly in young women who are about to undergo treatments or procedures that may affect their future fertility, such as chemotherapy for cancer.
Finally, it should be noted that although there are theoretical risks, freezing of sperm, eggs, and embryos is very safe. There have been no documented cases of infectious disease transmission, nor do the risks or birth defects, chromosomal anomalies, or pregnancy complications appear to be increased compared with using fresh sperm, eggs, or embryos.
Pregnancy rates, and more importantly live birth rates, are influenced by a number of factors, especially the woman’s age, number of embryos and cause of the infertility. But overall average success rates of IVF are around 30-50% per attempt.
Donor sperm, eggs, and embryos
IVF may be performed with a couple’s own eggs and sperm or with donor eggs, sperm, or both. A couple may choose to use a donor if there is a problem with their own sperm or eggs, or if they have a genetic disease that could be passed on to a child. Donors may be known or anonymous.
In most cases, donor sperm is obtained from a sperm bank. Both sperm and egg donors undergo extensive medical and genetic screening, as well as testing for infectious diseases.
Donor sperm is frozen and quarantined for six months, the donor is re-tested for infectious diseases including the AIDS virus, and sperm are only released for use if all tests are negative. Donor sperm may be used for insemination or in an ART cycle. Unlike intrauterine insemination (IUI) cycles, the use of frozen sperm in IVF cycles does not lower the chance of pregnancy.
Donor eggs are an option for women with a uterus who are unlikely or unable to conceive with their own eggs. Egg donors undergo much the same medical and genetic screening as sperm donors. Until recently, it has not been possible to freeze and quarantine eggs like sperm. Recent advances in oocyte freezing, though, have made this a possibility.
In some cases, when both the man and woman are infertile, both donor sperm and eggs have been used. Donor embryos may also be used in these cases.
A pregnancy may be carried by another woman who has no genetic relationship to the baby (gestational carrier). If the embryo is created by either IVF/ICSI technology using the infertile woman’s eggs & her husband’s sperm. This embryo is than transferred into the gestational uterus.
The gestational carrier will not be genetically related to the child. All parties benefit from psychological and legal counseling before pursuing surrogacy or a gestational carrier.
The decision to seek treatment for infertility is a viable one due to the assisted reproductive technologies available today. With patience, a positive attitude, and the appropriate treatment, most treatment, most infertile couples will eventually experience the joys of parenthood.
Dr Nandita Palshetkar
The author is a leading obstetrician and gynaecologist. Dr Palshetkar established assisted laser hatching in India in 1998. She also pioneered the IMSI and the spindle view technology.