Other causes include endometriosis (where tissue similar to the womb lining grows elsewhere, including the fallopian tubes or ovaries). This can distort the tubules and prevent the fimbriae (the tiny finger-like projections which ‘catch’ the released ovum and sweep it into the fallopian tube) from working properly.^5,10

Health conditions such as thyroid disorders (hyperthyroidism and hypothyroidism) can disturb menstrual patterns and ovulation. Adrenal abnormalities such as Cushing’s syndrome or congenital adrenal hyperplasia (with typically reduced cortisol and/or aldosterone levels, but excess androgens) can result in no egg being released during the menstrual cycle (anovulation).^5,11

In addition to problems caused by STIs, women with pelvic inflammatory disease (PID) may experience difficulties in conceiving. Chlamydia may spread to the womb, fallopian tubes or ovaries resulting in PID, increasing infertility risk, or making it harder to conceive. PID can also increase the risk of ectopic pregnancy, where the fertilised ovum implants into endometrial tissue not in the womb, most often in a fallopian tube, but very occasionally in an ovary, on the cervix, or in the abdomen.^5,12

Anovulation and amenorrhoea (the absence of menstrual periods) may also occur with long-term debilitating disease such as uncontrolled diabetes, cancer, end-stage kidney disease, or AIDS.⁵