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This method developed by Cohen in 1990, is generally carried aiming at improving embryo implantation rate. The process consists of making a puncture in the embryo’s external wall (pellucid zone) thus favoring a better embryonic fixation to the womb’s wall. It’s usually done in embryos generated following IVF.
The procedure utilizes micromanipulation techniques. In these cases an acid solution (Tyrode’s) or a laser beam may be used to make small 30 micrometers cut in the embryo’s wall. Indications for this process vary according to older age, small ovarian reserve, too thick zona pellucida, failure in previous IVF attempts, increase in the embryonic fragmentation, and reduced embryonic cleavage. A 15% increase in the gestation rate was observed in relation to cases without assisted hatching.
This procedure is aimed at placing the sperm and egg together inside the patient tube. Like the IVF an ovarian hyperstimulation is carried out to obtain a good number of follicles and eggs. At the proper moment eggs are aspired from ovary and 3 or 4 are selected. They are then placed together in a sperm solution inside a culture tube for few minutes.
At the same time a laparoscopy is conducted to view and access one of the fallopian tubes. As the tube is fixed with pincers the egg/sperm solution is injected with a thin catheter. In this process fertilization does not take place in vitro but in its natural environment which is the fallopian tube. In 1995 some 1,300 GIFT’s cycles were performed in the US reaching a 27.8% gestation rate.
One drawback in this process as compared to classic uterine transfer IVFs is that one cannot be sure if the fertilization process effectively occurred and the need for two surgical procedures with anesthesia: one to collect the eggs and then one to perform laparoscopy to place the gametes in the tube. As the gestation rates are about the same in both methods a drop in GIFT performance is observed in the last five years.
This method, also referred to as pro-nucleus stage tube transfer (PROST) is almost identical to the steps of GIFT. The only difference lays on fact that instead of transferring to the tube an egg/sperm solution, the embryo is transferred in its first fertilization stage – the zygote or pro-nucleus stage. To do so eggs and sperms are incubated for 24 hours to expect fertilization.
After ensuring fertilization succeeded the zygotes are transferred to the tube through laparoscopy as described before. Like in GIFT this method also requires two surgeries with anesthesia and one laparoscopy to place embryos in the tube.
A variant to ZIFT, embryo intrafallopian transfer or Tubal Embryo Transfer utilizes embryos in their second day post-fertilization (2 to 8 cells). Procedure is carried via vagina, without anesthesia, with the use of a special catheter that penetrates the uterus and then guided inside the fallopian tube.
Procedure is ultrasound-monitored to better view the catheter with the embryos location. In 33 procedures carried out with an average of 2.9 embryos transferred a 33% gestation rate was reached.
This is the most employed method when the male partner is unable to produce spermatozoids. It’s carried through the intrauterine insemination method described with semen sample of an anonymous donor chosen from a catalogue available at the semen bank. At our clinic we use São Paulo’s Albert Einstein Hospital semen bank. At their discretion couples pick a donor who gathers physical characteristics similar to the male partner. Samples are safely sent to our clinic in dry ice or liquid nitrogen. The gestation rate after 10 years employing this method averages 65%.
This technique is generally employed to improve the fertilization chances in older patients. The procedure consists of partially removing, through micromanipulation, older patients’ egg’s cytoplasm and replace it with part of cytoplasm removed from a younger patient’s egg. This will strengthen the older patient egg and improve fertilization and gestation rates.
This procedure still raises concern and has been banned in many countries due to the fact that the cytoplasm injected into the mother’s egg bears a fraction of the younger donor’s DNA. The claim is that the resulting embryo bears the DNA from three persons: the father’s sperm, the mother’s egg nucleus and part of the younger donor’s cytoplasm.
It is also a polemic and controversial method banned in some countries. Procedures are as previously described. Through micromanipulation the older patient’s egg nucleus, with all its genetic data, is removed and introduced into a younger woman’s egg. Through this method we can benefit from the younger egg potentialities with the genetic characteristics of the mother. Like in the cytoplasmic transfer part of the donor’s DNA goes into the new embryo, which again would be formed with the DNAs from three persons.
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