Assessment of ovarian reserve prior to IVF

In the female fetus oocyte numbers peak by 16 weeks of gestation, reaching up to 7 million. They decrease progressively and at the time of birth a female will have about 2 million eggs. As she approaches menarche the woman will have about 500,000. This primordial follicular disappearance continues throughout reproductive life and accelerates approximately 10 years prior to the menopause, by which time the number of eggs have fallen to a few hundred. If a woman ovulates one egg per month she will release 12 eggs per annum. Throughout her reproductive career (approximately 40 years, from the age of 10 to the age of 50) she will produce 480 eggs yet nature has given her 480,000 eggs to work with. At all stages of the menstrual cycle there are a number of small antral follicles present. This number changes with age, being at its highest in younger women. As the level of FSH rises at the beginning of the menstrual cycle more follicles are recruited and some are then selected for further development. One follicle, however, will be at the right condition for development and this “chosen” follicle will continue to develop till mid cycle when it ovulates. The quality of the released oocyte is related to both the age of the woman and the number of primordial follicles available in the ovary. Statistically speaking it is more likely for an egg to be of better quality if it is randomly “chosen”, for example, out of 100 competing primordial follicles than if it was randomly “chosen” out 10 competing primordial follicles. Follicle stimulating hormone (FSH) is crucial for follicular development as it is the hormone that controls the process of recruitment, selection and finally the full development of the maturing follicle. The number of primordial follicles available in the ovary influences the level of FSH. As the follicles are recruited, however, they secrete both estrogen and inhibin, which in turn keeps the level of FSH low. As women age, the number of recruited follicles decrease. Consequently the suppression of the FSH level decreases and, as a result, the level of FSH increases with age in an attempt to continue to recruit the ever-decreasing number of eggs within the ovary. The level of FSH provides a biological marker for ovarian reserve. The higher the level, the less the ovarian reserve. Consequently fewer primordial follicles will be recruited and the situation takes place as described above, with the “chosen” follicle sought from only a few competing ones. Oocyte quality is established early during fetal life. The first produced oocytes (less susceptible to non-disjunction) ovulate first and ‘poorer’ oocytes ovulate later. There is also evidence to suggest that there is age dependent damage in oocytes due to gradual increase in intracellular oxidative stress that also leads to increased frequency of nondisjunction. It is well documented that there is an age related reduction in fecundity due to reduction in pregnancy rate and rise in miscarriage rate. This is associated with an age related increase in aneuploidy due to non-disjunction. Age therefore results in reduction of both quality and quantity of oocytes. As discussed, the number of eggs available in the ovary is certainly reduced and the level of FSH is elevated as women age. The question here is: ‘If a woman at the age of 30 years, for example, has a Middle East Fertility Society Journal Vol. 12, No. 1, 2007 Copyright © Middle East Fertility Society