| Seven
steps for IVF |
- Preliminary
testing
- Development
of Oocytes (eggs)
- Oocyte
(egg) Retrieval
- Sperm
Collection and Insemination
- Incubation
and Fertilization of Eggs
- Formation
and cleavage of embryos
- Embryo
transfer
- Cropreservation
(freezing) programme
|
| Introduction
: |
|
In vitro fertilisation1 (IVF) is a technique
in which egg cells are fertilised outside the woman's body.
IVF is a major treatment in infertility where other methods
of achieving conception have failed.
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|
The process involves hormonally controlling the ovulatory process, removing ova (eggs) from the woman's ovaries and letting sperm fertilise them in a fluid medium. The fertilised egg (zygote) is then transferred to the patient's uterus with the intent to establish a successful pregnancy. "In vitro" is Latin for "in glass", referring to the test tubes, however neither glass nor test tubes are being used; the term is used generically for laboratory procedures. |
| Indications
: |
|
Initially
IVF was developed to overcome infertility due to problems
of the fallopian tube, but it turned out that it was successful
in most other infertility situations as well. The introduction
of intracytoplasmic sperm injection addresses the problem
of male infertility to a large extent.
Thus,
for IVF to be successful it may be easier to say that it requires
healthy ova, sperm that can fertilise, and a uterus that can
maintain a pregnancy. Cost considerations generally place
IVF as a treatment when other less expensive options have
failed. |
| Oocyte
retrieval |
|
When
follicular maturation is judged to be adequate, human chorionic
gonadotropin (ß-hCG) is given. This agent, which acts
as an analogue of luteinising hormone, would cause ovulation
about 42 hours after injection, but a retrieval procedure
takes place just prior to that, in order to recover the egg
cells from the ovary. The eggs are retrieved from the patient using a transvaginal |
|
technique involving an ultrasound-guided needle piercing the vaginal wall to reach the ovaries. Through this needle follicles can be aspirated, and the follicular fluid is handed to the IVF laboratory to identify ova. The retrieval procedure takes about 20 minutes and is usually done under conscious sedation or general anaesthesia. |
|
| IVF
laboratory |
|
In
the laboratory, the identified eggs are stripped of surrounding
cells and prepared for fertilisation. In the meantime, semen
provided by the male partner is prepared for fertilisation
by removing inactive cells and seminal fluid. The sperm and
the egg are incubated together (at a ratio of about 75,000:1) in the culture media for |
|
about 18 hours. By that time fertilisation should have taken place and the fertilised egg would show two pronuclei. In situations where the sperm count is low a single sperm is injected directly into the egg using intracytoplasmic sperm injection (ICSI). The fertilised egg is passed to a special growth medium and left for about 48 hours until the egg has reached the 6-8 cell stage. |
| Embryo
transfer |
The
embryos judged to be the "best" are transferred
to the patient's uterus through a thin, plastic catheter,
which passes through her vagina and cervix. Often, several
embryos are passed into the uterus to mprove chances of implantation
and pregnancy. |
|
| Post
- Transfer |
The
patient has to wait two weeks before she returns to the clinic
for the pregnancy test. During this time she may receive progesterone—a
hormone that keeps the uterus lining thickened and suitable
for implantation. This hormone is secreted from the pituirity
gland and also is known as the hypophysis. Many IVF programmes provide
additional medications as part of their protocol. |
| Pregnancy |
|
The
chance of a successful pregnancy is approximately 25-35% for
each IVF cycle. Although selected clinics are now able to
quote rates up to 50% per cycle. There are many factors that
determine success rates
including the age of the patient, the quality of the eggs
and sperm, the duration of the infertility, the health of
the uterus, and the medical expertise. It is a common practice
for IVF programmes to boost the pregnancy rate by placing
multiple embryos during embryo transfer.
A flip side of this practice is a higher risk of multiple
pregnancy, itself associated with obstetric complications.IVF
programmes generally publish their pregnancy rates, however
comparisons between clinics are difficult as many variables
determine outcome. Furthermore, these statistics depend strongly
on the type of patients selected.
|
| Complications |
|
The
major complication of IVF is the development of multiple births.
This is directly related to the practice of placing multiple
embryos at embryo transfer. Multiple births are related to
increased pregnancy loss,
premature labour, obstetrical complications, prematurity,
and neonatal morbidity with the potential for long term damage.
Strict embryo transfer policies have been enacted to reduce
this problem, but are not niversally followed or accepted.
Spontaneous splitting of embryos in the womb
after transfer does occur, but is rare (1%) and would
lead to identical twins. Recent evidence suggest that singleton
offspring after IVF is at higher risk for lower birth weight
for unknown reasons.Another
major complication, related to the use of ovarian stimulation
is the evelopment of the ovarian hyperstimulation syndrome.
If
the underlying infertility is related to abnormalities in
spermatogenesis, it is plausible, but too early to examine
that male offspring is at higher risk for sperm abnormalities. |
| Developments |
|
Intracytoplasmic
sperm injection (ICSI) is a more recent development associated
with IVF which allows the sperm to be directly injected in
to the egg using micromanipulation. This is used for sperm
that have difficulty penetrating the egg and when sperm numbers
are very low. ICSI results in success rates equal to IVF fertilisation.
Preimplantation
genetic diagnosis (PGD) can be performed on embryos prior
to the embryo transfer. |
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