CausesBy Mayo Clinic staff
In order for you to become pregnant, each of these factors is essential:
- You need to ovulate. Achieving pregnancy requires that you're having regular menstrual cycles during which an egg is released, a process known as ovulation. Your doctor can help evaluate your menstrual cycles and confirm ovulation.
- Your partner needs sperm. For most couples, this isn't a problem unless your partner has a history of illness or surgery. Your doctor can run some simple tests to evaluate the health of your partner's sperm.
- You need to have regular intercourse. You need to have regular sexual intercourse during your fertile time. Your doctor may be able to help you better understand when you're most fertile during your cycle.
For pregnancy to occur, every part of the complex human reproduction process — from the ovary's release of a mature egg to the fertilization of the egg to the fertilized egg's implantation and growth in the uterus — has to take place just right. In women, a number of factors can disrupt this process at any stage. Female infertility is caused by one or more of these factors.
Ovulation disorders account for infertility in 25 percent of infertile couples. These can be caused by flaws in the regulation of reproductive hormones by the hypothalamus or the pituitary gland, or by problems in the ovary itself. You have an ovulation disorder if you ovulate infrequently or not at all.
- Abnormal FSH and LH secretion. The two hormones responsible for stimulating ovulation each month — follicle-stimulating hormone (FSH) and luteinizing hormone (LH) — are produced by the pituitary gland in a specific pattern during the menstrual cycle. Excess physical or emotional stress, a very high or very low body weight, or a recent substantial weight gain or loss — for instance, 10 percent of your body weight — can disrupt this pattern and affect ovulation. The main sign of this problem is irregular or absent periods. Much less commonly, specific diseases of the pituitary, usually associated with other hormone deficiencies or with excess production of prolactin, may be the cause.
- Polycystic ovary syndrome (PCOS). In PCOS, complex changes occur in the hypothalamus, pituitary and ovary, resulting in overproduction of male hormones (androgens), which affects ovulation. PCOS can also be associated with insulin resistance and obesity.
- Luteal phase defect. Luteal phase defect happens when your ovary doesn't produce enough of the hormone progesterone after ovulation. Progesterone is vital in preparing the uterine lining for a fertilized egg.
- Premature ovarian failure. This disorder is usually caused by an autoimmune response, where your body mistakenly attacks ovarian tissues. It results in the loss of the eggs in the ovary, as well as in decreased estrogen production.
Damage to fallopian tubes (tubal infertility)
When fallopian tubes become damaged or blocked, they keep sperm from getting to the egg or close off the passage of the fertilized egg into the uterus. Causes of fallopian tube damage or blockage can include:
- Inflammation of the fallopian tubes (salpingitis) due to chlamydia or gonorrhea
- Previous ectopic pregnancy, in which a fertilized egg becomes implanted and starts to develop in a fallopian tube instead of in the uterus
- Previous surgery in the abdomen or pelvis
Endometriosis occurs when tissue that normally grows in the uterus implants and grows in other locations. This extra tissue growth — and the surgical removal of it — can cause scarring, which impairs fertility. Researchers think that the excess tissue may also produce substances that interfere with conception.
Cervical narrowing or blockage
Also called cervical stenosis, this can be caused by an inherited malformation or damage to the cervix. The result is that the cervix can't produce the best type of mucus for sperm mobility and fertilization. In addition, the cervical opening may be closed, preventing any sperm from reaching the egg.
Benign polyps or tumors (fibroids or myomas) in the uterus, common in women in their 30s, can impair fertility by blocking the fallopian tubes or by disrupting implantation. However, many women who have fibroids can become pregnant. Scarring within the uterus also can disrupt implantation, and some women born with uterine abnormalities, such as an abnormally shaped (bicornuate) uterus, can have problems becoming or remaining pregnant.
In some instances, a cause for infertility is never found. It's possible that combinations of minor factors in both partners underlie these unexplained fertility problems. The good news is that couples with unexplained infertility have the highest rates of spontaneous pregnancy of all infertile couples.
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