Ovarian Reserve: Understanding Its Role in Female Fertility"

 What is ovarian Reserve?

varian reserve refers to the quantity and quality of a woman’s eggs, which naturally decline with age. It is assessed through biomarkers such as Anti-Mullerian Hormone (AMH) levels, antral follicle count (AFC), and follicle-stimulating hormone (FSH) levels. A low ovarian reserve reduces fertility potential, making conception more difficult.

According to the American Society for Reproductive Medicine (ASRM), ovarian reserve reflects reproductive lifespan, with egg quantity decreasing progressively from birth and accelerating after the mid-30s.  

The World Health Organization (WHO) estimates that infertility affects 15 per cent of reproductive-age couples globally, with diminished ovarian reserve (DOR) being a significant contributing factor.

 Prof. Engin Oral, a leading expert in reproductive medicine, emphasised that ovarian reserve is crucial in reproductive planning, particularly for women with conditions like endometriosis and polycystic ovary syndrome (PCOS). Detecting a decline early allows for timely interventions such as egg freezing or assisted reproductive treatments.

 Natural aging, genetics, heavy smoking, early menopause, childhood ovarian issues, and reproductive conditions like ovarian endometriosis all have an impact on ovarian reserve. Surgical procedures like endometrioma surgery can also negatively impact ovarian reserve,” says Prof. Oral.

While ovarian reserve naturally declines with age, there is no medical tool to determine its quality, only its quantity. Moreover, once diminished, it cannot be increased. Oral advises women to measure their ovarian reserve early and pay attention to symptoms like heavy bleeding, menstrual pain, and irregular periods. Endometriosis, a chronic condition affecting millions of women worldwide, has long been linked to infertility. A critical factor emerging in research is its relationship with ovarian reserve, a key determinant of reproductive potential.

 Ovarian endometriosis, also known as an endometrioma or ‘chocolate cyst,’ occurs when endometrial-like tissue grows inside or on the ovaries. This can result in cysts filled with thick, dark brown fluid. According to the Journal of Ovarian Research, ovarian endometriosis accounts for 17–44 per cent of endometriosis cases, depending on the population studied and the diagnostic methods used.

 Endometriosis causes a chronic inflammatory environment in the pelvis, leading to oxidative stress that damages ovarian tissue and reduces the pool of healthy eggs. “Endometriosis contributes to ovarian damage in multiple ways, significantly impacting ovarian reserve,” Prof. Oral explained.

 Surgery, a common treatment for endometriomas, also poses risks. “If not performed carefully, surgical excision can remove healthy ovarian tissue along with the cyst, further reducing egg count,” he warned. The condition can also impair ovarian blood flow, accelerate ovarian decline and disrupt hormonal regulation, affecting ovulation and fertility.

 Dr Ezekiel Mecha, a lecturer at the Department of Biochemistry, University of Nairobi and an endometriosis expert, says, “Not all women with endometriosis experience diminished ovarian reserve. The risk is mainly in those with ovarian or bilateral endometriosis.” According to research, these two varieties have a direct effect on ovarian reserve, whereas other varieties may or may not affect egg quantity. A study in Fertility and Sterility found that women with ovarian endometriomas experience a 30–40 per cent decline in ovarian reserve, reinforcing the need for early diagnosis and treatment.

 Women with endometriosis often struggle with infertility, and a declining ovarian reserve exacerbates the problem. “Many women seek fertility treatments only after years of failed natural conception, often when their ovarian reserve is already critically low,” Prof. Oral stated.

 Endometriosis-related infertility arises from multiple factors, including painful menstruation and intercourse, which may indicate underlying complications. Adenomyosis, where endometrial tissue grows into the uterine wall, can disrupt implantation. Inflammation and scarring may cause tubal blockage, preventing egg and sperm from meeting. Deep endometriosis, which infiltrates beyond the pelvic lining, can severely affect reproductive organs, making natural conception more challenging.

Doctors assess ovarian reserve using various tests. The number of follicles in both ovaries is measured by sonographic antral follicle count, and hormone tests measuring FSH, luteinizing hormone (LH), oestradiol, and AMH provide additional insights into ovarian function. A lower-than-normal follicle count may indicate diminished ovarian reserve, while a higher count could signal PCOS.

 For women with diminished ovarian reserve, fertility treatment and preservation options exist. In vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI) improve pregnancy chances, while egg freezing allows women to preserve fertility for the future. “Early diagnosis and intervention empower women to take control of their reproductive future,” Prof. Oral said.

 For those trying to conceive, assisted reproductive technologies (ART) such as IVF offer a viable option. However, lower ovarian reserve means fewer eggs available for retrieval, affecting success rates. Prof. Oral recommended early intervention, including fertility preservation strategies for women diagnosed with endometriosis in their reproductive years.

 In Kenya, endometriosis is increasingly recognised as a leading cause of infertility. However, awareness remains low, leading to delayed diagnosis and limited access to specialised reproductive healthcare. To improve fertility outcomes, the Kenya Obstetrical and Gynecological Society (KOGS) emphasizes the need for improved diagnostic tools and early interventions. Although endometriosis can reduce the quantity and quality of eggs, IVF success rates remain comparable between women with and without the condition. A study in Human Reproduction found no significant differences in fertilisation rates or live birth outcomes between both groups. Prof. Oral confirmed that IVF remains an effective treatment option, with frozen embryo transfer showing slightly improved success rates for endometriosis patients.

 Dr Mecha emphasised that ovarian reserve tests are useful but not absolute predictors of fertility. AMH levels, for instance, can fluctuate due to individual health factors and laboratory conditions, making repeated testing necessary for accuracy. “A single test may not provide a complete picture,” he explained.

 Similarly, antral follicle count depends on high-quality ultrasound imaging and trained professionals, which may not always be accessible in resource-limited settings. While these tests offer valuable insights into ovarian reserve, they only measure egg quantity, not quality. “Ovarian reserve tests help estimate egg quantity but do not reveal egg quality, which is critical for successful conception,” Prof. Oral emphasised.

 Despite its impact, ovarian reserve decline often goes unnoticed until fertility problems arise. “By the time many women receive a diagnosis, their ovarian reserve may already be significantly diminished. We need to shift towards proactive fertility management,” Oral says.

 Women should monitor their ovarian reserve early and seek medical advice if they experience irregular cycles, painful periods or fertility concerns. They may be able to navigate their reproductive journey more effectively with the assistance of individualized treatment plans, regular screenings, and consultations with fertility specialists. The link between ovarian reserve, reproductive conditions like endometriosis, and infertility underscores the need for a proactive approach to reproductive health. With expert insights, women can make informed decisions about their fertility before time becomes a limiting factor. Early diagnosis, careful management, and timely intervention can make a significant difference in preserving fertility and improving the chances of conception for women affected by endometriosis.

Ovarian Reserve

The number and quality of a woman's eggs in her ovaries, which determines her fertility potential, is referred to as her ovarian reserve. According to the World Health Organization (WHO), women are born with about 1 to 2 million eggs, but this number declines over time, dropping to around 300,000 to 500,000 by puberty. The American College of Obstetricians and Gynecologists (ACOG) states that fertility starts decreasing significantly after the age of 35 due to a natural decline in egg quantity and quality. Throughout her reproductive years, only about 300 to 500 eggs will be ovulated, while the rest are lost naturally.

 Egg loss happens naturally through ovulation and atresia, a process where multiple eggs begin to develop each month, but only one matures and is released while the rest break down and are absorbed by the body. According to the Centers for Disease Control and Prevention (CDC), external factors such as ovarian surgery, chemotherapy, and smoking can accelerate this decline. Certain medical conditions like endometriosis, genetic disorders and autoimmune diseases can also reduce ovarian reserve more quickly.

 Although menstruation does not directly reduce ovarian reserve, the overall reproductive cycle does. Each month, about 10 to 20 eggs are recruited, but only one or two mature, while the rest are lost. This process continues until menopause, when fewer than 1,000 eggs remain, and menstruation stops. The natural breakdown and absorption of unused eggs occur throughout a woman’s life, even before puberty. Medical and external causes, such as exposure to toxins, ovarian removal, and certain genetic disorders, can also contribute to a faster decline in ovarian reserve.

 Currently, there is no proven way to increase ovarian reserve in terms of quantity, as women are born with a finite number of eggs. However, lifestyle changes like maintaining a healthy diet, avoiding smoking and managing stress may help preserve egg quality. Some fertility treatments, such as ovarian stimulation through hormone therapy, can temporarily enhance egg development for conception purposes, but they do not increase the total number of eggs available.