Monday, 24 March 2014

Things you need to know about Ovarian Reserve

Ovarian reserve

The proportionality of age and female fertility depends on the capacity of ovary to produce enough eggs capable of fertility and ovarian reserve is the term used to define the above. Biologically, women are born with a defined number of eggs that deplete with age. With every passing month, the number of eggs decreases (with best eggs ovulated first) and the incidence of eggs with abnormal chromosomes (aneuploidy) increases. As a result, the older women have lower fertility and greater risk for miscarriage than younger women. “Ovarian reserve” generally describes the size, quality, and developmental potential of the remaining eggs in the ovary.

Low Ovarian Reserve

Ovulation cycle of a woman starts in early, with development of millions of eggs. Majority of these eggs before a woman decides to enter reproduction cycle. At birth, a female has around one to two million eggs at birth, which falls to 250,000 to 500,000 eggs at puberty. At 37 years of age, a woman will only have estimated 25,000 eggs and at menopause less than 1000.

Causes of Low Ovarian Reserve

Basic two reasons that leads to the decrease in number of eggs can be, chromosomal anomalies such as Turner Syndrome, where there the woman does not have two X chromosomes, or gene abnormalities such as Fragile X. Second, if the ovarian tissue is destroyed through torsion, surgical removal of part or the entire ovary, ovarian cysts caused by endometriosis, benign or malignant ovarian tumors, radiation or chemotherapy, immunological conditions, pelvic adhesions, or a high body mass index.

Problems in IVF due to low ovarian reserve

Low ovarian reserve can result in problems in conceiving and even miscarriage. The rate of IVF success depends on number of eggs the doctor can obtain at the egg retrieval. Women, who respond poorly to the stimulation, produce fewer mature follicles resulting in three times less chance of pregnancy. Old women produce less number of eggs and most of them are of poor quality. And, embryos formed from such eggs either decreases the chances pregnancy or increases the chances of miscarriages.

Tests to determine Ovarian Reserve

There are certain tests to determine the remaining egg supply in a women, Basal AntralFollicle Count test is one such test, in which, a transvaginal ultrasound test is performed to determine woman’s ovarian reserve. The female ovarian reserve determines the fertility potential. Females are born with a lifetime limited number of eggs in their ovaries in the time of birth. Puberty is the inception of egg release and by the time a woman reaches menopause, her egg supply (and potential fertility) is exhausted.

An antral follicle is a small, fluid-filled sac that contains an immature egg. The follicles can be seen, measured and counted on Cycle Days 2, 3, and 5 by using ultrasound. The number of eggs retrieved correlates directly with IVF success rates. When an average to high number of antral follicles (eight or more) are visible on the ultrasound, the good number of eggs are retrieved for IVF. If few antral follicles appear, a poor response is expected and the IVF cycle might be delayed or withheld.

Another test for testing ovarian reserve is Anti Mullerian Hormone (AMH) test. The test can be performed on any day of a woman’s cycle. AMH is a hormone produced by granulosa cells in ovarian follicles. Women with higher AMH values will tend to have better response to ovarian stimulation for IVF.  Women with lower AMH have lower antral follicular counts and produce a lower number of oocytes (eggs).

AMH test level do not determine the quality of egg. Having more eggs at the IVF egg retrieval provides an opportunity for a greater number of eggs to fertilize and develop into embryos.  More eggs do not always mean more embryos.  Egg quality is an important aspect of fertilization and development of embryos.  So, both the above tests are performed before IVF to determine the ovarian reserve.

Dr Neeraj Pahlajani

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