Women's fertility: All you need to know about egg freezing

CHENNAI: Cryopreservation (freezing) of embryos, oocytes, sperms and gonadal tissue is the process of freezing and depositing them in liquid nitrogen at -196 degrees Celsius, for storage and use at a later date after a procedure known as thawing.

A widely known yet less aware and acknowledged fact is the age-related decline in fertility.

A woman’s fertility is ideal in her early 20 to 30 years of age and is inversely proportional to age, with a rapid decline in fertility after 35 years of age.

A girl baby has around 1 to 2 million oocytes at birth and rapidly decreases to 3 to 4 lakhs at puberty. In each menstrual cycle, only one oocyte or egg matures, sufficient for a woman's reproductive years.

Doctors say that the advantage of egg freezing is fertility preservation in women with a cancer diagnosis who need to undergo gonadotoxic chemotherapy, in women susceptible to premature menopause and for women who choose to delay marriage and conception, with cryosurvival rate of oocyte being high 80 to 90 per cent, fertilisation rates of 60 to 70 per cent comparable to fresh oocytes. There can be procedure-related disadvantages but they can be treated.

Dr S Gayathri Devi, Consultant Obstetrics and Gynaecology, Rela Hospital says that Cryoperservation of embryos has enabled embryo transfer at a later date, thereby saving a woman from a rare but life-threatening complication of controlled ovarian hyperstimulation in an IVF cycle, improves pregnancy success rates and giving time for preimplantation genetic diagnosis when medically indicated".

She explains that the process of egg freezing starts with controlled ovarian hyperstimulation of the ovaries which means you will get daily hormone injections for 11 to 14 days, to stimulate the ovaries to form more eggs in a single menstrual cycle, an electively scheduled minor procedure under anaesthesia called oocyte to pick up.

Dr Gayathri explains that follicular fluid from the formed oocytes is retrieved vaginally under ultrasound guidance to isolate mature oocytes from the follicular fluid in the embryology lab and vitrify the oocytes and store the oocytes in a straw labelled with your name, date, number of eggs being stored and hospital ID number, in liquid nitrogen.

There are two methods of freezing – slow cooling and vitrification, the latter is preferred for its added advantage. Vitrification of oocytes involves mobilisation of water out of the cell and diffusion of added cryoprotectants into the cell, ultra-rapid cooling through the use of liquid nitrogen, which transforms oocytes into a clear, glass-like structure. Oocyte storage for up to 10 years is allowed as per the new ART law in India, beyond which permission is mandatory from the National ART Board.