Causes of infertility in women can vary, and in some cases a cause cannot be identified (known as unexplained infertility). Most common causes are explained in this article.
Damage to fallopian tubes (tubal infertility)
An egg released by the ovary during ovulation moves to the fallopian tube and remains there alive for about 24 hours. Fertilization happens when a single sperm meets the egg in the fallopian tube. The fertilised egg then slowly moves down the fallopian tubes and gets implanted to the lining of the uterus.
Blocked or damaged fallopian tube would prevent sperm from reaching an egg or it would block movement of fertilized egg to uterus, resulting in infertility. Main factors that can cause blocks or damages in fallopian tubes are: endometriosis, pelvic inflammatory disease, ectopic pregnancy (a condition in which a fertilized egg gets implanted to fallopian tube instead of uterus and starts growing there) and surgery in abdomen or pelvis.
Cervical blockage and cervical mucus defect
Cervix connects uterus to vagina. Cervical blockage, also referred to as cervical stenosis, is a condition in which cervical canal is partially or fully blocked. This could result in defective mucus production in cervix harmfully affecting sperm mobility. In worst cases, the blockage would even prevent sperm from entering the uterus.
Scarring in the uterus and presence of fibroids (benign non cancerous tumors) in or around uterus can block fallopian tubes or disrupt implantation of fertilized egg to uterus lining. Some women are born with uterine abnormalities that cause them problems in getting pregnant or remaining pregnant.
Ovulatory disorders are one of the most common causes of infertility in women. Two main types of ovulatory disorders are: Polycystic Ovarian Syndrome (PCOS) and Primary Ovarian Insufficiency (POI) also known as Primary Ovarian Failure.
Polycystic ovarian syndrome (PCOS) is a condition in which a woman’s sex hormones are out of balance. Ovaries in women produce a small amount of male sex hormone called androgen. PCOS occurs when ovaries produce higher levels of androgen causing a hormonal imbalance, interfering with the ability of ovary to produce mature eggs. Researchers think that family genetics and insulin resistance(insulin is a hormone which helps the body to convert sugar, starch and other forms of food to energy) are the main reasons of PCOS. Small ovarian cysts are formed in ovaries of those suffering from PCOS and hence the name.
Primary Ovarian Insufficiency (POI) is a condition in which ovaries stop producing eggs before a woman turns 40. POI is accompanied by high levels of Follicle Stimulating Hormone (FSH). Follicle Stimulating Hormone (FSH) is a hormone produced by the pituitary gland. A high level of FSH is an indication of poor egg quality and it is a signal that a woman’s egg supply is diminishing (also known as low ovarian reserve). POI and high FSH levels can be results of: aging (FSH levels start to rise naturally about 10 years before a woman enters menopause), hereditary factors, pituitary gland disorders, exposure to radiation or chemotherapy, Turner syndrome also known as fragile X chromosome, Graves disease, conditions affecting endocrine system such as Polycystic Ovarian Syndrome (PCOS), autoimmune disorders or genetic conditions such as Galactosemia.
Low Progesterone Levels
Low progesterone levels can cause infertility in women. Progesterone plays a crucial role in regulating the menstrual cycle and preparing the uterus for conception and pregnancy. Low progesterone level prevents implantation of fertilized egg to uterus lining or survival of the embryo, resulting in miscarriage.
Endometriosis occurs when tissues (made of endometrial cells) that normally grows inside the uterus start growing outside the uterus in locations such as ovaries, fallopian tubes and lining of the pelvic cavity. These malformed tissue implants break down and shed during menstruation resulting in bleeding. Since these tissues are outside uterus, blood cannot flow out of the body through vagina (as it happens in the case of menstrual blood). This could result in scarring and cyst formation, thereby making it difficult for ovary to release an egg or for a fertilized egg to get implanted into the womb.
Exact causes of endometriosis are unknown. Theories about causes of endometriosis can be found here.
Pelvic inflammatory disease (PID)
Pelvic inflammatory disease (PID) infects a woman’s reproductive organs such as fallopian tubes, uterus, ovaries or cervix. PID usually occurs as a complication of sexually transmitted diseases such as chlamydia or gonorrhea. PID can lead to inflammation, scarring and blockage of fallopian tubes, causing infertility.
Poor egg quality
Poor egg quality can prevent successful fertilization from happening. Egg quality declines with age. Other factors that can lead to poor egg quality are: smoking, exposure to radiations or chemotherapy, health problems and genetics.
Use of non-steroidal anti-inflammatory drugs (NSAIDS) can harmfully affect ability of women to conceive. NSAIDS can fail ovarian follicles from bursting and releasing eggs. Click list of NSAIDS for more information.
Other causes of infertility in women
Other factors that can cause infertility in women are: aging, infections of thyroid gland, autoimmune diseases, chemotherapy, use of anti psychotic medicines and illegal drugs such as marijuana or cocaine, being overweight or underweight, overly intense exercise, stress, excessive drinking, smoking, sexually transmitted diseases (STD), occupational and environmental factors such as exposure to harmful substances or temperature.