Ovarian reserve refers to the total number of eggs present in the ovaries of a female at a given time. A low ovarian reserve means a situation in which there is a decrease in the number of eggs to such an extent that it interferes with a pregnancy.
Most of the time, a low ovarian reserve is a result of the normal process of aging but other reasons may also be present. It is possible to have a low ovarian reserve with an intact ovarian function.
Where do all the Eggs Go?
When a female is born, her ovaries already have developed millions of eggs. However, the number of these eggs reduce to a great extent before they are even required for reproduction purposes.
In utero, a speedy multiplication of the germ cells begins at up to eight weeks. As a female fetus acquires the age of 16 to 20 weeks, her ovaries have about seven million eggs. This number decreases to nearly two million eggs as the female is born.
Till the time a girl hits her puberty, the total number of eggs present in her body has fallen down to merely 25,000. This further decrease to only a thousand eggs at menopause.
There are three different types of eggs present in an ovary; immature eggs, eggs out of which a few eggs are recruited and prepared for ovulation in a certain cycle, and lastly the dead or atrophic eggs.
These eggs are encapsulated by follicles that nourish them till the time they mature. However, most of the eggs never make it to maturity. Every month, a specific number of immature eggs are recruited for maturation. Only one if these eggs further ovulate whereas the rest of them are regressed and reabsorbed by the ovary.
The total number of eggs selected by the ovaries depends on the number of immature cells present in the pool.
What are the Causes of a Low Ovarian Reserve?
Low ovarian reserve refers to a decrease in the total number of eggs prematurely. It can be caused by certain chromosomal anomalies such as Turner Syndrome or certain genetic problems like Fragile X.
Moreover, any harm to ovarian tissue due to any trauma or torsion, or the surgical removal of any part of it can lead to a low ovarian reserve.
In some cases, endometriosis, ovarian tumors and cysts, chemotherapy, radiotherapy, and pelvic adhesions are some of the reasons why you may be suffering from a low ovarian reserve.
Low Ovarian Reserve and IVF
The low ovarian reserve is a problem when it starts making it difficult for you to get pregnant. Most of the women suffer from this condition in their 30’s or 40’s when they have already had children so, it does not bother them much.
In vitro fertilization is a way of managing low ovarian reserve and the success of this treatment plan depends on the number of eggs that a doctor can collect at the egg retrieval.
A woman in which only three of lesser mature follicles form in the ovaries after ovarian stimulation is said to be a poor responder. The chances of getting pregnant reduce by three folds if the doctor obtains less than four eggs from a woman.
Fewer eggs indicate that there are fewer embryos to choose for an embryo transfer. In some cases, poorly responding women are older in age so their egg quality is also poor. This further decreases the chances of getting pregnant and increases the risk of miscarriages.
The response of a patient to ovarian stimulation is proportional to their total ovarian reserve.
How to Identify a Poor Responder
There are a number of baseline tests used to check if a woman is a poor responder. These include checking:
- Inhibin B
- Follicle-stimulating hormone (FSH)
- Antral follicle count
- Anti-Mullerian hormone
Some dynamic tests such as the Clomiphene Citrate Challenge Test and the exogenous follicle stimulating hormone reserve test also exist to identify the potential patients.
Once a diagnosis has been established, the next step is to determine the most suitable stimulation protocol in a patient.
The most important factor is to recruit as many eggs as possible. There is no such thing as a perfect protocol. This is because a vast variability of responses exists between the poor responders towards the same protocol.
There is no such procedure that fits all the patients and most of the time, it is better to try different protocols and settle for the best one.
Some examples of different stimulation protocol include:
- Estrogen in the luteal phase of the last menstrual cycle
- A low dose of HMG/FSH stimulation
- Letrozole an HMG/FSH
Growth hormone can also help as an adjunct to the stimulation, however, GHRF (growth hormone releasing factor, oral L-arginine, DHEA, transdermal testosterone, and acupuncture cannot seem to do this.
How to Decide the Treatment and Stimulation Protocol?
One of the most important factors to be considered while deciding whether or not a woman must be treated is her age. The implications of this treatment are different for a 35-year-old female who produces one or two eggs than a 45-year-old female who produces a similar number of eggs.
Unfortunately, age does not only affect the number of eggs in a female but also its quality.
The doctor is required to lower the FSH levels at day 2 in case it is more than that recorded at day 15. Generally speaking, if the level of FSH recorded at day 2 is higher than that recorded at ay 15, the chances of having more than 2 eggs are extremely less.
This is caused due to two important phenomena that tend to occur with time:
- A decrease in the total number of eggs present in the ovaries
- A decrease in the quality of eggs present in the ovaries
It is also a usual practice to check the Antral Follicle Count at the first day of a planned stimulation. If the count comes out to be one or two, the chances of having more than 2 eggs are very less irrespective of the drugs given to the patient.
An evaluation test is performed to assess the anti-mullerian hormone (AMH) and the antral follicle count (AFC) to investigate if stimulating the ovaries is of any use. The levels of AMH tells about the total number of eggs in the ovaries. A higher number of AMH indicates a larger number of eggs.
If your ovarian reserve is low, you are not likely to get more than one or two follicles. In such cases, a doctor may suggest an IVF cycle to you. It is extremely important to be realistic regarding the chances of success so that the couple can opt for an appropriate treatment decision.
A poor ovarian response means having lesser than expected number of egg in the ovaries, usually less than three. It is important for a doctor to know this as the total number of eggs produced during ovarian stimulation decides the success rate of a particular treatment, mostly IVF.
If there is a patient who is likely to be a poor responder, her ovarian stimulation protocol must be adjusted in order to increase the total number of eggs formed inside her ovaries.
It is possible to treat a reduced ovarian reserve but requires the use of right treatment protocols.