MEDICINE FOR ALL

Approaches of oocyte recovery

In the early days of IVF experimentation, abdominal laporatomy was performed to collect oocytes during tubal ligation procedures. Surgery would be scheduled immediately prior to expected ovulation, timed by basal body temperatures. Follicles were extracted by needle aspiration or ovarian wedge resection. Techniques described for follicle aspiration involved puncturing follicles over 5 mm in diameter with a 20-gauge needle. The aspiration needle was connected to tubing and emptied into a test tube through a metal inlet with a rubber stopper sealing the tube. A second needle was introduced through the stopper and connected to surgical suction tubing via a three-way plastic connector. Aspiration was achieved by covering the free opening in the three-way connector to create suction to 200 mmHg. Each follicle was aspirated into individual tubes. The techniques described for wedge resection involved incising follicles with a scalpel under microscopy subsequently releasing the oocytes into the culture medium for further observation. Using these techiques, these reported oocyte recovery rate was 30.2% for aspiration  and 93.3% for wedge resection. Although these techniques are a viable option  to obtain oocytes, laparotomies carry surgical risks to include bleeding, infection, increased pain, potential injury to surrounding pelvic and abdominal organs, and longer recovery times. The risks of laparotomy to retrieve oocytes for IVF encouraged the pursuit of alternative surgical options.

Approaches of oocyte recovery 

Oocyte recovery aims to maximise the number of oocytes extracted from the ovarian follicles while minimizing the surgical risk to the patient. Optimizing this balance has driven the evolution of oocyte recovery techniques.

In the nearly 40 years since the first successful human birth, ART has undergone continuous improvement. Significant advances have been made in oocyte fertilization and embryo culture , resulting in ever-increased treatment success. Often overlooked, however, have been the developments in oocyte recovery and embryo transfer techniques that have led to increased safety and success of ART treatment. This document sets out to review the history oocyte recovery and embryo transfer techniques, and to provide recommendations for current best practices.

The history of assisted reproductive technology (ART) dates  back more than a century when Walter Heape, a professor at the University of Cambridge, reported the first case of embryo transfer in Rabbits in 1890s. Several decades later, Aldous Huxley conceptualized the technique of in vitro fertilization (IVF) in his science fiction novel Brave New World (c.1932). After successful mammalian experiments, attempts at human IVF began in 1940s when Miriam Menken and John Rock exposed human oocytes recovered via laparotomy to spermatozoa in vitro. Three decades later, Louise Brown was born after successful IVF.

Oocyte  retrieval is most safely accomplished with conscious sedation via a transvaginal approach under ultrasound guidance with low-pressure aspiration. Follicle flushing has not been shown to improve outcomes. As the final step in embryo transfer is essential. Based on current findings, the recommended embryo transfer technique includes the use of an ultrasound-guided transcervical approach with a full bladder using a soft catheter. The transfer depth of the embryo  should be in the mid portion of the uterus with a quick steady insertion followed by pressure on the syringe during withdrawal  of the catheter. It is acceptable to encourage immediate ambulation after embryo transfer.

Decisions

• Embryo freezing

Unless you have ethical objections, they recommend you request to freeze any good quality ‘spare’ embryos. They culture spare embryos to day 5 so that only embryos that have demostrated their ability to keep developing are frozen.

Decisions

• At what stage to transfer embryos?

Embryos are usually transferred on day 3 or day 5 after egg collection. If there are several embryos of similar quality on day 3, then culturing to day 5 gives better information on which is the best embryo to transfer.

Decisions

• How many embryos to transfer?

The important facts to keep in mind are:

1. Up to and including the age of  40, the chance of twins with two embryos back is around 25-30%
2. Between the ages of 41 and 44, the chance of twins with two embryos is around 10-15%
3. Even with one embryo back, 2% of pregnancies are identical twins, and even identical triplets have been reported
4. With modern embryo freezing methods, 90-95% of embryos survive freezing and thawing. When the embryo survives freezing and thawing, its chance of pregnancy is very similar to that of a fresh embryo. 

Decisions

• How many embryos to transfer?

A woman’s body is designed to carry one baby at a time. As we mentioned before, twins are associated with 2-3 times more risk for both the mother and child for a broad range  of adverse outcomes, from maternal death, still-birth to cerebral palsy.

Transfer of one embryo is now standard for women 40 years and younger , and strongly recommended for women 41 and older. Single embryo transfer is required for almost all publicly funded treatment.

Decisions

You and your doctor will need to make several decisions about your in vitro fertilization cycle before you start treatment. There are recorded in the doctor’s management plan, and those with an ethical aspect are also recorded in your consent form.

• How many eggs to add sperm to?

On average 75% of mature eggs fertilize normally in in vitro fertilization and ICSI. Unless you have an ethical objection to discarding ‘poor quality’ embryos or to freezing  ‘spare’ embryos.