Egg Maturation in the Lab

In vitro fertilization has helped hundreds of thousands of couples to achieve pregnancy and live births. Although initial efforts at in vitro fertilization in the 1960s attempted to mature eggs in the laboratory, these techniques were largely unsuccessful. The first live birth from in vitro fertilization obtained a single egg that was matured inside the ovary. No fertility medications were used. This “natural cycle” in vitro fertilization was gradually replaced by stimulated in vitro fertilization using various fertility medications since it was shown that when a larger number of eggs were retrieved, a larger number of embryos could be created. This allowed for selection of the best embryos for transfer into the uterus and as a result pregnancy rates improved.

However, the use of fertility medications for ovarian stimulation has become extremely expensive. In addition, some women are extremely sensitive to the effects of these medications and, as a result, can develop a potentially life-threatening condition known as ovarian hyperstimulation syndrome (OHSS). Finally, there are some women who have cancers that are hormonally responsive and therefore must avoid the high hormone levels that result from ovarian stimulation.

Clearly, there is a great need to develop better techniques to perform in vitro fertilization without the use of fertility medications. In 1991, physicians in Korea reported the first pregnancy from eggs that were obtained from an ovary at the time of a cesarean section and then matured in the laboratory. In 1994, another pregnancy was established using immature eggs that were obtained from women with polycystic ovary syndrome.

Recent improvements in culture conditions and techniques have led to a great improvement in the likelihood for in vitro matured eggs to produce viable embryos.

The technique involved for in vitro maturation begins with a woman having a transvaginal ultrasound performed between day 3 and 5 of her menstrual cycle. If she does not have evidence for regular menstrual cycles and natural ovulation, she would be a candidate for in vitro maturation alone. If she has regular ovulatory cycles, then she is a candidate for natural cycle in vitro fertilization combined with in vitro maturation.

An injection of hCG is given and the eggs are retrieved 36 hours later. The immature eggs are placed in a petri dish containing specialized media to help the eggs mature. Once the eggs are matured, they are injected with sperm - this is a fertilization technique known as ICSI . The injected aggs are now cultured for several additional days to allow the embryos to develop. This is the same technique that is used in standard in vitro fertilization. 

During this time, the female is given hormones to prepare the uterine lining. Both estrogen and progesterone are given after the ggs have been retrieved.  A few embryos are then selected and an embryo transfer is performed. 

In vitro maturation results 

Women who had ovulatory cycles are first monitored until they are though to be at a point just before ovulation. This enables the physician to potentially obtain one or two mature eggs in addition to the immature eggs. Using this technique, a similar live birth rate was obtained by the same Canadian group.

As with all fertility treatment, success rates are lower for older women. Using in vitro maturation, the pregnancy rates for women above age 35 were very low. Thus these women are not good candidates for this technique.