| from
the book How to Have a Baby: Overcoming Infertility
by Dr. Aniruddha Malpani, MD and Dr. Anjali Malpani,
MD.
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Test Tube Babies - IVF & GIFT (Page 4)
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GIFT stands for gamete intrafallopian transfer and this
used to be a popular alternative to IVF in the past.
A gamete is a male or female sex cell - a sperm, or
an egg. During GIFT, sperm and eggs are mixed and injected
into one or both fallopian tubes. After the gametes
have been transferred, fertilization can take place
in the fallopian tube as it does in natural, unassisted
reproduction. Once fertilized, the embryo travels to
the uterus by natural processes.
As in IVF, a GIFT treatment cycle begins
with ovulation enhancement which is followed by egg
harvest, usually by means of laparoscopy. But the similarity
to IVF ends here. In IVF, an embryo is transferred.
In GIFT, gametes are transferred.
Only patients with at least one normal,
healthy fallopian tube are candidates for GIFT. These
include women who have unexplained infertility or mild
endometriosis and couples whose infertility results
from male, cervical, or immunological factors. Some
doctors recommend that couples with male factor infertility
proceed with GIFT only if it has been proven that the
man's sperm can fertilize the woman's egg either by
in vitro fertilization or by past pregnancies.
The basic steps of GIFT are superovulation , egg harvest,
insemination, and gamete transfer. The eggs are usually
harvested during laparoscopy. During this same laparoscopy
procedure, which takes about an hour , eggs are mixed
with sperm and the gametes are transferred.
Insemination
The harvested eggs are examined under the microscope
and graded for maturity. The selected eggs are placed
in individual dishes and combined with sperm (insemination).
The sperm are prepared in advance in the same manner
as for IVF. Some doctors prefer to allow the dishes
to sit for about 10 minutes before the transfer, since
during this period the sperm adhere to the zona pellucida
of each egg. Many programs load eggs and sperm individually
into a catheter and inject them into one or both of
the fallopian tubes.
Gamete Transfer
The sperm egg mixture is loaded into a specially designed
catheter . This is then directed into the fallopian
tube(s) through their fimbrial opening while looking
through the laparoscopy. Up to four eggs and sperm may
be injected into one or both tubes. Gametes will be
transferred only if the fallopian tubes appear healthy.
If the surgeon determines that the tubes are unhealthy,
IVF should be attempted instead. For this reason, GIFT
should be undertaken only at facilities that have the
capability to do IVF.
Specialists generally agree that pregnancy rates are
higher for GIFT than for IVF- in fact, GIFT is about
twice as successful as IVF. In part, this may be due
to the type of patient accepted into GIFT programs.
It may also be because the in vivo tubal environment
is more "physiologic " for the gametes and embryo than
the in vitro environment.
The advantages of this technique are
:
- the fallopian tube acts as the laboratory
- the embryo will reach the uterus
at a later stage in its development, as with normal
conception.
- the procedure is considered morally
acceptable to some religious groups which object to
IVF, as conception occurs within the human body.
- the endometrium will also be more
receptive to the embryo because of the greater time
the embryo takes to reach the uterus.
There are several differences between GIFT and IVF.
The most important one is that GIFT requires at least
one healthy fallopian tube, whereas IVF is appropriate
treatment for women with tubal disease or even no fallopian
tubes at all. At present, GIFT requires laparoscopy
for transfer, while an IVF treatment cycle can be completed
without laparoscopy. This is one of the reasons many
IVF clinics no longer offer GIFT , even though it offers
a higher pregnancy rate - because they do not have easy
access to an operation theatre. Ideally, you should
opt for treatment in a clinic which offers all the procedures,
so that the doctor can select the one which is best
for you, depending upon your individual circumstances.
In the case of GIFT, fertilization occurs
unobserved inside the body. With IVF, fertilization
takes place in a laboratory dish and can be confirmed
visually with a microscope. Visual confirmation of fertilization
is especially important in cases of male factor or unexplained
infertility. To obtain visual confirmation and still
have the greater chance of pregnancy afforded by GIFT,
one of the variations of GIFT described later (ZIFT,
PROST or TET) may be used, to give the patient the benefit
of combining the advantages of both the procedures.
A major disadvantage with conventional GIFT is that
a surgical procedure - laparoscopy - is needed to transfer
the eggs and sperm into the fallopian tube. Recently,
a non-surgical method has been described by Dr. Jansen
and Anderson from Sydney IVF, Australia, in which the
gametes can be transferred into the fallopian tubes
through the vagina and cervix under ultrasound guidance.
This requires a special set of catheters which allow
the doctor to enter the uterine ends of the fallopian
tubes through the cervix. Once the catheters have been
accurately positioned - and ultrasound can help in this
- the gametes are injected into the tubes. Since this
does not involve surgery, the benefits to the patient
are obvious - less expense, no hospitalization, no scar
and no anesthesia. However, the technique does require
much more technical expertise and is still being investigated
more thoroughly. Also, the pregnancy rates with the
method are less than with conventional laparoscopic
GIFT.
Variations of GIFT include procedures with names like
ZIFT ( ZIFT
Video ) , PROST, TET - an alphabetic potpourri !
ZIFT, zygote intrafallopian transfer,
is also called PROST, which stands for pronuclear stage
transfer. When a sperm penetrates an egg, the sperm
introduces its nuclear material into the egg. Approximately
14 hours after penetration, two distinct pronuclei,
one from the sperm and one from the egg, are visible
under the microscope. Pronuclei are taken as indicators
that fertilization has occurred. A zygote is a fertilized
egg before cell division begins. For ZIFT ( ZIFT Video ) , eggs
are removed by transvaginal aspiration and fertilized
in a laboratory dish. The next day, when the fertilized
eggs have reached the pronuclear stage, the embryos
are transferred to the fallopian tubes during laparoscopy.
Approximately 24 hours after a fertilized
egg reaches the pronuclear stage, it divides for the
first time and becomes a two cell embryo. This cell
division is called cleavage. It is at this stage or
later that TET, tubal embryo transfer, may be attempted.
The fertilized and dividing egg (early cleavage stage
embryo) is transferred to the fallopian tube during
laparoscopy.
PROST, ZIFT, and TET differ from GIFT
in that fertilization takes place in a laboratory dish
instead of the fallopian tube. Moreover, they differ
from IVF in that the fertilized egg is transferred to
the fallopian tube instead of to the uterus. They offer
the best of both IVF and GIFT - documentation of fertilization
in vitro; and higher pregnancy rates because of tubal
transfer. However, the cost of ZIFT, PROST, or TET is
usually greater than IVF or GIFT
continued
. . .
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Tube Babies - IVF & GIFT (Page 6)
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Test Tube Babies - IVF & GIFT (Page 4)
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