It is estimated that about 90% of primordial follicles are lost by the age of 30. This suggests that most women start trying to get pregnant in a condition of depleted ovarian reserve. Consequently, this can lead to infertility and childlessness. Therefore, availability of fertility preservation services is becoming a major health necessity for some women. Thanks to recent advances in oocyte vitrification, long before women made reproductive decisions, it became possible to preserve fertility effectively. However, due to a number of factors that include lack of public consent, insufficient awareness of patients and clinicians, economic costs and organizational problems, fertility preservation services are not always available.
In principle, the way to care for cryopreservation of oocytes can be divided into 4 major stages: a) preliminary evaluation, b) controlled ovarian stimulation, c) oocyte retrieval and cryopreservation, and d) post-treatment counseling. Preliminary assessment is vital, given that the effectiveness of subsequent management steps is determined largely by this assessment. In addition, pre-treatment counseling provides an excellent opportunity to develop an understanding with the patient, which can be invaluable in the treatment of patients undergoing potentially stressful treatment.
Interventions for pre-assessment to oocyte cryopreservation were discussed below, reflecting the reader’s journey in the real clinical settings. The merit of each intervention was evaluated, considering its effectiveness.
A thorough preliminary assessment should include the following steps: a) history taking, b) physical examination, c) pelvic ultrasound scan, d) the ovarian reserve evaluation, e) genetic testing, and f) pre-treatment counseling.
The choice of treatment interventions can vary depending on the patient’s characteristics and expectations. Thus, the reason for requesting the cryopreservation of oocytes and the outcome patient expect from treatment should be established. For example, the pathway for treating a young patient who wants to preserve fertility before reaching career goals may be different from the pathway in someone with a family history of premature ovarian insufficiency (POI). Therefore, it is important to understand the reasons for the need for cryopreservation of oocytes.
A general health history should be created to assess the safety of ovarian stimulation and oocyte retrieval procedures, as well as the consequences of a future pregnancy on the health of the patient. Reproductive history includes age in menarche, duration of menstrual cycles, date of last menstrual cycle, use of contraceptives, previous gynecological pathologies, and previous obstetric history. In the context of social history, clinicians can look for whether the patient is in stable relationships, the patient’s plans for future fertility, or if there are any social problems that could affect the plans for creating a family.
It is important to note that risk factors for the loss of the ovarian reserve should be established. The assembly of the primordial follicles determines the ovarian reserve during the embryonic and fetal period, as well as the subsequent rate of loss of oocytes, which appear to be influenced largely by genetic, ecological, lifestyle, and medical factors. There is a significant relationship between maternal age in menopause and the ovarian reserve of a woman. Therefore, the establishment of this, and the reproductive history of the patient’s mother and sisters gives important information about the genetic predisposition of the patient to the POI.
The influence of environmental factors on the ovarian reserve has not been fully studied. However, there is strong evidence that some agents, such as radiation and gonadotoxic chemicals, have harmful effects. Similarly, some lifestyle factors, such as smoking, affect the ovarian reserve in the patient, as well as the reproductive function in general. The role of certain medical factors on the ovarian reserve can be divided largely into 3 broad medical modalities: a) radiation therapy, b) chemotherapy, and c) surgical intervention on the ovaries. Although all these interventions appear to have a negative effect on the ovarian reserve, there is a significant difference between the effects of individual treatments. For example, some chemotherapeutic agents exhibit a strong gonadotoxic effect, while others may lead to a moderate and temporary cessation of the patient’s reproductive function.
Similarly, the duration, as well as the dose of chemotherapeutic agents, are also recognized determinants of the subsequent ovarian reserve. Thus, obtaining a detailed history of the impact of genetic, environmental, vital and medical factors on the accelerated loss of the ovarian reserve provides important information about the current and future fertility of the patient, which plays a vital role in advising an individual patient about preserving their fertility.
The basic anthropometric measurements, such as height, weight and body mass index (BMI) allow to assess the overall well-being of the patient. However, the role of BMI in understanding of individual patient’s ovarian reserve is less clear. While some believe that a higher BMI is associated with lower AMH, others have found that obese women have significantly higher levels of Anti-Müllerian Hormone (AMH), antral follicle count (AFC), and lower levels of follicle-stimulating hormone (FSH) that indicates a direct correlation between weight and the ovarian reserve.
Pelvic pathology can have a significant impact on both oocyte cryopreservation cycle and future fertility treatment. Therefore, the presence of pathology of the uterus, tubes and ovaries should be excluded prior to oocyte cryopreservation treatment cycle. Therefore, ultrasound scanning should be used as a screening tool. In addition, ultrasound scanning offers one of the best tools for assessing the ovarian reserve, which has a number of advantages over other markers of the ovarian reserve.
The Ovarian Reserve Evaluation
The biological ovarian reserve is defined as the number of primordial and growing follicles left in the ovary at any given time, and therefore the establishment of a true biological ovarian reserve is clearly impractical in clinical settings. However, the ovarian reserve can be assessed using various biomarkers, such as the chronological age, FSH, AMH, and AFC. Although these markers provide the best available representation of patient’s ovarian reserve, it is important to assess the strengths and limitations of these markers so that they are interpreted in the context of the overall characteristics of the tests, rather than in absolute numbers.
The Ovarian Reserve
The ovarian reserve is determined by the size of the oocyte pool at birth and the decrease in the number of oocytes thereafter. Both these processes are largely influenced by genetic factors, although the role of environmental and life-style factors appear to play a role. Folliculogenesis in women of reproductive age consists of two stages: a) the initial non-cyclic set of primordial follicles leading to the formation of primary and pre-antral follicles, and b) the cyclic development of antral follicles followed by the selection of a single dominant follicle.
While the mechanism of initial oocyte recruitment was not well understood, AMH appears to be the main regulator of the size of the primordial pool of follicles by its inhibitory effect on the recruitment of primordial follicles. The cyclic phase of oocyte development is characterized by the transformation of secondary follicles into antral follicles and the subsequent growth of antral follicles into pre-ovulatory stages. In general, the process of cyclical recruitment begins from puberty under the influence of increasing levels of pituitary FSH.
AMH also inhibits the development of growing follicles and it appears that AMH inhibits the growth of follicles caused by FSH, by reducing the sensitivity of growing follicles to FSH. Thus, AMH and FSH play a vital role in recruiting and growing follicles, which is supported by the state of the ovarian reserve, given time that is largely determined by the age of the woman. Therefore, the measurement of these parameters, namely AMH, FSH, AFC, and age, provides a window into the state of ovarian activity, as well as the total ovarian reserve in women.
Because of the biological age-related decline in the number and possibly the quality of the oocytes, the chronological age can be used as a marker of the ovarian reserve. The ovarian reserve, natural fertility and the results of ART are significantly reduced from the age of 35, when it is believed that the ovarian reserve is subject to accelerated decline. Although there is a strong link between chronological age and fertility decline, it is obvious that there is a significant variation in the age-related ovarian reserve, indicating that a chronological age alone may not be sufficient to estimate reliably the ovarian reserve in each woman.
Basal FSH was one of the first endocrine markers to be introduced into the fertility assessment and is still used in many IVF clinics, although in combination with other markers that are considered more reliable. FSH secretion is determined largely by the effect of negative feedback of steroid hormones, especially estradiol, and inhibins, which are expressed in granulosa cells of growing ovarian follicles. Therefore, decreased or diminished recruitment of ovarian follicles is associated with an increase in serum FSH and high, especially very high basal FSH reading, is considered a good marker of very low or reduced ovarian reserve.
However, unlike some other markers, FSH measurements do not appear to have the discriminatory capacity to categorize patients in different bands of the ovarian reserve.
Antral Follicle Count
Evaluation of the basal antral follicle involves ultrasound evaluation of the ovaries between the 2nd and 4th days of the menstrual cycle and the counting of “follicles”, which corresponds to the antral stage of folliculogenesis. The test provides a direct quantitative assessment of the growth of follicles and is known as one of the most reliable markers of the ovarian reserve. It is reported that AFC measurement has similar sensitivity and specificity to AMH in predicting poor and excessive ovarian response in IVF cycles. Given that the AFC measurement is available instantly and allows patients to be immediately assigned, the test eliminates the need for additional patient visits prior to the IVF cycle.
However, AFC is usually performed only in the early follicular phase of the menstrual cycle. The variability of AFC during the menstrual cycle is small, especially when counting follicles 2-6 mm and therefore evaluating the AFC without regard to the menstrual cycle day can be feasible.
Like other markers of the ovarian reserve, the AFC appears to demonstrate significant variability between measurements in the same patient.
In female, AMH produced by granulosa cells of pre-antral and early antral ovarian follicles, regulates the recruitment of oocytes and folliculogenesis. It can assess the ovarian reserve and guide gonadotropin stimulation in ART cycle. AMH is also used as a tumor marker for granulosa cells, a tool for assessing the ovarian reserve after chemotherapy, and to predict age at menopause.
Both the formation and the reduction of the ovarian reserve are largely determined genetically, and therefore the extremes of low ovarian reserve, such as POI and early menopause, are of genetic origin. POI can be present as a sign of certain genetic syndromes that can be diagnosed by their non-ovarian phenotype. However, chromosomal abnormalities, mosaic of sex chromosomal abnormalities, pre-mutation alleles of FMR1, and other rare mutations, are associated with primary premature ovarian failure without other phenotypic traits. When POI is suspected, it is recommended to conduct appropriate genetic testing, including referral to clinical genetics.
Patients who are concerned about their risk of POI should be referred for genetic counseling. Pre-symptomatic or carrier genetic testing will depend on the family history, the patient’s medical history and their desire for genetic testing.
The most relevant studies are karyotyping and allele size in the FMR1 gene. Analysis of repeats in the FMR1 gene is recommended as a biased or prenatal screening of carriers in women with a family history of X-fragile, undiagnosed mental retardation, developmental delay, autism or ovarian insufficiency.
In addition, extended screening of carriers can be considered, including the analysis of frequent mutations in genetic conditions. Thus, genetic testing in patients suffering from fertility preservation for ovarian aging is determined by the family history of POI, the symptoms of genetic signs associated with premature loss of the ovarian reserve, and the results of the assessment of the ovarian reserve.
After a complete assessment, the patient should be able to consult individually before treatment. This should include a discussion of the clinical effectiveness, cost, constraints and logistics of oocyte preservation. Patients should be provided with information leaflets written in plain language in a format accessible to patients.