Oocyte cryopreservation for the modern woman
Recent birth statistics show an increased delay in childbirth until much later . This trend is largely due to women pursuing PG degrees and higher level of professional achievements that demand time and effort.
It is a well known fact that fertility rates drop after 35 years and when they finally decide to conceive , it might sometimes be too late.
The number of oocytes a woman can have keeps dropping from birth . Oocytes are about 7 million during 20 weeks inside the womb , about two million at birth and 200,000 at the onset of puberty after which they reduce in accelerated rates .The average age of menopause is 51, at which time there are approximately 1000 oocytes remaining.
Other factor to consider is that the quality of oocytes also declines and eventually reaches a critical threshold below which pregnancy is no longer possible.
The silver lining in all this is the ability of the uterus to successfully host a pregnancy is maintained much after her reproductive years.This is the only reason why embryo cryopreservation is such a sought after treatment option for women looking at delaying pregnancy.
Embryo cryopreservation is a proven method of fertility preservation ever since the first cryopreserved embryo resulted in a live birth in 1983.
There is no known time limit for the duration of embryo storage; a live birth was achieved following transfer of embryos that had been cryopreserved nearly for 20 years.
Live birth rates from frozen embryos/eggs depends mostly on the age of the woman during egg retrieval.
The process of oocyte freezing inclines blood tests , hyper stimulation of ovaries followed by oocyte retrieval and then cryopreservation.
The common investigation include ovarian reserve testing , infectious disease screening along with pre-operative testing.
Injectable medications are prescribed to cause a hyper stimulation of the ovaries to produce more follicles.
Egg retrieval is done under anaesthesia using a trans-vaginal ultrasound probe where all the follicles are retrieved using a suction device.
The common dictum is lesser the age of the woman during retrieval , more are the chances of getting good number of follicles.Shortly after the eggs are harvested, they’re cooled to subzero temperatures to preserve them for future use.This process is called vitrification.
Available data comparing births resulting from previously frozen oocytes with those from fresh oocytes have not shown an increased risk of congenital anomalies. More long-term data, however, will be needed to further assess these risks.
Ideal candidates for oocyte freezing
- Women with cancer requiring chemotherapy
- Surgery that may damage the ovaries
- Risk of premature ovarian failure
- Ovarian disease which may damage follicles
- Fertility preservation for social or personal reasons to delay childbearing.