生殖補助医療(ART)
For many couples trying to conceive unsuccessfully, there are a range of advanced fertility treatments known as Assisted Reproductive Technologies, including in vitro fertilization (IVF ). With many factors affecting the source of your difficulties, you may be advised to follow one of these.
In Vitro Fertilization (IVF)
Hormonal injections are given to stimulate the production and release of eggs. The eggs and sperm are united in a laboratory dish, from which the process takes its name. In Vitro is Latin for in glass. If the eggs fertilize, a pre-determined number of embryos will be transferred into the woman’s uterus. Hopefully, one will implant and begin to develop.
Generally IVF can be described in five steps:
Step One: Ovarian stimulation
The goal is to help ripen several mature egg cells by stimulating the ovaries with injected hormones for several days. This is necessary because not every egg cell is fertilized and not every embryo develops or implants in the uterus. Regular ultrasounds and blood tests allow the doctor to observe the number and size of follicles maturing and the thickness of the uterus lining. When ultrasound monitoring indicates that the egg cells inside the follicles are close to ripening, another hormone is injected to induce final follicle maturation and ovulation.
Step Two: Egg retrieval
Egg cells must be retrieved within 36 to 38 hours of the follicle maturation induction. Otherwise, the egg cells will disappear and become inaccessible to complete the treatment. Egg retrieval is usually carried out via the vagina under ultrasound guidance, using a long hollow needle.
Step Three: Fertilization
The same day of egg retrieval, a fresh semen sample is provided by masturbation and refined in the laboratory to optimise sperm capabilities. The egg and sperm cells are then united in a Petri dish (or with ICSI procedure) and cultivated in an incubator for 24 hours. If fusion takes place, the fertilized eggs are left to mature for another 2-3 days for embryo transfer, or 5-6 days for blastocyst transfer.
Step Four: Embryo transfer
One or more embryos are transferred back into the uterus using a soft fine tube attached to a blunt syringe loaded with the embryo(s). The procedure, performed in the clinic, is relatively simple and painless.
Step Five: Luteal phase support
After embryo transfer the woman is given hormones, which the body normally produces during the second half of the menstrual cycle. This thickens the lining of the uterus to prepare it to accept implantation of a fertilized egg.
A pregnancy test is performed about 14 days after embryo transfer and, if positive, an ultrasound scan is performed two weeks later.
| Up to 30% of patients undergoing ovarian stimulation have a mild case of ovarian hyperstimulation syndrome (OHSS).1 In moderate OHSS, patients may develop or accumulate fluid within the abdominal cavity, experience pains in the abdomen, nausea and gastrointestinal symptoms. If you experience these symptoms, notify your doctor at once. Typically mild OHSS can be managed with over-the-counter painkillers and a reduction in activity.1 Severe over-stimulation may require admission to hospital. However, regular monitoring reduces the risk of side effects to 2%1 or less. |
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Intracyto-plasmic Sperm Injection (ICSI )
This laboratory procedure is often used in conjunction with in vitro fertilisation if the male partner has very low sperm count, low sperm motility or poor-quality sperm.
Using microscopic guidance, a laboratory technician injects a single sperm directly into an egg cell. If fusion takes place, the embryo is transferred into the uterus for implantation.
Other treatments
Gamete Intra-Fallopian Transfer (GIFT)
This treatment follows the same procedures as IVF except that fertilization occurs in the body (in vivo, within the fallopian tubes). GIFT can only be practised if the fallopian tubes are healthy.
| Fertilization cannot be immediately verified since GIFT takes place in vivo. |
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Zygote Intra-Fallopian Transfer (ZIFT)
This treatment follows the same procedures as IVF except that the fertilized eggs are placed in the fallopian tube at a specific early stage of embryo development.
| ZIFT can only be conducted if the fallopian tubes are healthy. |
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Testicular Sperm Extraction (TESE) and Microsurgical Epididymal Sperm Aspiration (MESA)
In some cases, for example where the sperm ducts are blocked, there are no sperm at all in the ejaculate. It may still be possible however, to obtain sperm directly from the testicles (TESE ) or from the epididymis (MESA ). A minor surgical procedure is carried out to remove tissue samples, which may contain sperm. These procedures require local anaesthesia and are not usually painful. The sperm is then used in ICSI treatment.
| Usually enough sperm can be retrieved from one procedure to be frozen for later use if required. |
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Assisted hatching
Prior to implanting in the uterus, the embryo must emerge from its covering in a process called hatching. In some women, the membrane seems to harden with age, interfering with the hatching process.
In such cases, piercing the embryo membrane with a dilute acidic solution or laser prior to embryo transfer may assist hatching. This procedure is performed to embryos in the laboratory when needed. Older women or those who have not achieved pregnancy after several IVF cycles are often helped by this treatment.
| Prepare yourself to undergo multiple treatment cycles. Pregnancy is a result of a complex combination of factors and events. Even if doctors are able to identify the barriers preventing pregnancy, conception still takes a degree of luck. Many couples go through multiple cycles to conceive. |
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Egg and embryo freezing
Cryopreservation, also known as freezing, involves storing eggs or embryos at a very low temperature so they can be used later. It allows for a further treatment cycle without having to repeat the process of hormonal stimulation and egg cell retrieval.
| The risk of multiple pregnancies with infertility treatments is higher than usual but can be minimized. Currently on average 21% of pregnancies resulting from IVF and ICSI are twins and 1% are triplets.2 This is primarily due to the practice of transferring several embryos into the uterus to increase chances for success. Discuss with your doctor ways to minimize the risk of multiple pregnancies. |
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Egg donation
Egg donation involves another woman donating her eggs so that a recipient,who is unable to use her own eggs, may conceive. In egg donation, IVF is performed in the usual manner, except that the donor receives the medication to stimulate egg production.
At the same time, the recipient also receives medication so that her cycle mirrors that of the donor and her body is prepared to receive the embryo. The eggs are then fertilized in a laboratory using the recipient partner’s sperm and the embryos are transferred into the recipient’s uterus.
| Fertility treatment is time-consuming and at times, extremely stressful. Couples go through a range of intense emotions. Moods can swing from hope to fear, from joy to disappointment. Talk about your feelings and find out how to support your partner. |
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Preimplantation Genetic Diagnosis (PGD)
PGD is a technique that can be used during IVF to test embryos for a variety of genetic disorders. Testing is done in the laboratory before the embryo is transferred to the uterus. This decreases the risk of having a child with a serious inherited disorder. Screening can detect a range of disorders, including Down’s syndrome, cystic fibrosis, haemophilia A, Tay-Sachs disease, and Turner syndrome. PGD is indicated only in some well defined conditions.
| There’s no absolute success rate for fertility treatments and averages may be misleading. It depends on many factors, including your age, the cause of your difficulties in conceiving and the expertise of doctors. |
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1. Assisted Reproductive Technologies. A Guide for Patients. ASRM 2008; http://www.asrm.org/Patients/patientbooklets/ART.pdf 2. ESHRE. The European IVF monitoring programme (EIM), for the European Society of Human Reproduction and Embryology (ESHRE). Assisted reproductive technology in Europe, 2005. Results generated from European Registers by ESHRE. Hum Reprod 2009; 24:1267-1287.
