Female anatomical reasons for infertility

Infertility statistics

Infertility is a serious and heartbreaking issue for many around the globe. About 48.5 million couples experience infertility worldwide, and in the United States nearly 1 in 7 couples are affected — meaning they’ve been unable to conceive after at least a year of frequent, unprotected intercourse. Although society often looks first to the woman, it’s just as important to look at the male partner. In developed countries, an estimated 37% of couples’ infertility is attributed to the female only, 8% to the male only, and 35% to both partners.¹

This is the first article in a two-part series on the causes of infertility and what can be done about them; here we focus solely on female anatomical reasons. Its companion covers the anatomical causes of male infertility.

Signs of female infertility

Aside from an inability to conceive, a few signs suggest infertility may be a potential issue. They may include:

• Irregular periods
• Painful or heavy periods
• No periods
• Hormone-fluctuation symptoms — facial hair growth, reduced libido, skin issues, weight gain
• Pain during intercourse

There are a number of anatomical issues that cause infertility among women, accounting for about 40% of the reasons women in developed countries are infertile. When addressing infertility, anatomical reasons should always be explored and ruled out or addressed first. We describe five of the most common below.

1. Tubal abnormalities

Tubal abnormalities — also called tubal factor infertility — refer to a blockage or adhesion in the fallopian tubes. The tubes can be completely blocked, have just one blocked side, or carry scarring that narrows them.² Clear fallopian tubes matter for pregnancy because they transport the egg from the ovary to the uterus each month, allow sperm to pass through, and carry a fertilized egg back to the uterus for implantation.

Between 25–30% of women who have an infertility evaluation have tubal abnormalities. The biggest cause is pelvic inflammatory disease (PID), which can travel from the cervix to the uterus to the tubes. A previous ectopic pregnancy may also cause them, as can infections such as chlamydia and gonorrhea, other diseases like endometriosis and tuberculosis, and abdominal surgery or a burst appendix.²

2. Endometriosis

Endometriosis occurs when tissue that normally lines the uterus grows in places outside of it — including the ovaries, fallopian tubes, or intestines. It’s a very common condition that causes both pain and infertility, though 20–25% of women who have it are asymptomatic.³ Roughly 6–10% of women have endometriosis, 30–50% of women who have it are infertile, and among women diagnosed as infertile, 25–50% have endometriosis.⁴ A variety of immunological, genetic, and environmental factors are thought to be at play.³

Proposed causes

• Retrograde menstruation — menstrual blood containing endometrial cells flows back through the fallopian tubes into the pelvic cavity, where the cells stick and thicken.
• Transformation of peritoneal cells (“induction theory”) — cells lining the abdomen transform into endometrial-like cells due to hormones or immune factors.
• Embryonic cell transformation — estrogen or other hormones transform embryonic cells into endometrial-like implants during puberty.
• Surgical scar implantation — after surgery, endometrial cells attach to a surgical incision.
• Endometrial cell transport — blood vessels or tissue fluid carry endometrial cells to other parts of the body.
• Immune system disorder — a dysregulated immune system fails to recognize and destroy endometrial-like tissue growing outside the uterus.
• Hormone imbalance of estrogen and progesterone — with endometriosis, progesterone and estrogen signaling are disrupted, resulting in low progesterone and estrogen dominance, which drives inflammation, pelvic pain, and reduced implantation. Endometrial cells thrive on estrogen and make their own; high estrogen is a marker of endometriosis.

Symptoms

• Painful periods
• Painful intercourse
• Pain with urination or bowel movements
• Excessive bleeding — heavy periods, bleeding between periods, or both
• Fatigue, diarrhea, constipation, nausea, or bloating — especially during menstruation

Many women who have endometriosis also have irritable bowel syndrome (IBS) and multiple food intolerances — such as gluten, soy, caffeine, legumes, and dairy — and these digestive issues often become worse during menstruation.

Treatment may include hormones or surgery (both electrosurgery and laparoscopic surgery). Hormones may reduce symptoms, but there’s less evidence they improve pregnancy outcomes; surgical removal of endometriotic implants appears to offer better chances of a successful pregnancy. If pregnancy doesn’t follow surgery, in vitro fertilization and embryo transfer (IVF-ET) has been a successful next step for many women.⁶ Diet may also play a role: increasing omega-3s, vitamin D, and antioxidants while avoiding inflammatory foods like gluten and trans fats may reduce pelvic pain and could potentially support a positive pregnancy outcome, particularly alongside surgery.⁷

3. Uterine myomas (fibroids)

Uterine myomas — better known as fibroids — can distort the uterine cavity, reduce the surface area for implantation, and cause inflammation. They affect 20–50% of women of reproductive age. Symptoms can include heavy or prolonged periods and pelvic pain, though in some cases there are none. Fibroids affect fertility by distorting the cervix and uterus, impeding egg movement, or blocking the fallopian tubes.⁸ The exact cause is hard to pinpoint, but hormones, growth factors (such as insulin-like growth factor), and genetic changes within fibroids are believed to play a role.⁹

Treatment options

• Myomectomy — surgical removal of fibroids. You may need to wait 3 months before trying to conceive, and it may increase the chance of cesarean delivery.
• Myolysis — uses a laser, radio-frequency energy beam, or electric current to shrink the blood vessels feeding the fibroids.
• Hormonal birth control pills — may ease symptoms but can increase fibroid size, and prevent pregnancy while used.
• Intrauterine device (IUD) — may ease symptoms but won’t reduce fibroids, and prevents pregnancy.
• Gn-RH agonists — shrink fibroids, but block the hormones needed for ovulation and menstruation, so conception isn’t possible while on the medication.

4. Pelvic adhesions

Pelvic adhesions occur when scar tissue causes internal organs to stick to one another — the uterus, ovaries, fallopian tubes, bladder, and intestines. They can bind different organs together (such as the uterus to the ovaries) or bond within an organ (such as one part of the uterine wall to the opposite side).¹² They’re often caused by pelvic surgery or infection: PID frequently leads to adhesions in the fallopian tubes, and severe endometriosis may also cause them.¹²

5. Congenital uterine anomalies

During development in utero, a female baby’s uterus forms as two separate halves that fuse together before birth. In fewer than 5% of women the uterus forms abnormally, which is when congenital uterine anomalies occur. Anomalies may include the two halves remaining separate (didelphys), only one half developing (unicornuate), a normal surface with a slight indentation into the cavity (arcuate), an indented surface with two endometrial cavities (bicornuate), or a normal surface with two endometrial cavities (septate).¹³ Though they affect fewer than 5% of women, they’ve been noticed in up to 25% of women who have miscarriages or premature births and can also increase the risk of infertility.¹⁴