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Clinical Review ABC of subfertility

Unexplained infertility, endometriosis, and fibroids

BMJ 2003; 327 doi: (Published 25 September 2003) Cite this as: BMJ 2003;327:721
  1. Roger Hart, UK subspecialist in reproductive medicine and senior lecturer in obstetrics and gynaecology, fellow of the Royal Australian and New Zealand College of Obstetricians and Gynaecologists
  1. university of Western Australia school of women's and infant's health, King Edward Memorial Hospital, Subiaco, Australia


    The presence of patent fallopian tubes, normal ovulation, and normal sperm parameters may still be associated with subfertility because of distortion of the uterine cavity or the presence of intraperitoneal endometriosis. Frustratingly, in some cases, no abnormality is found on routine investigation and the infertility is labelled “unexplained.”

    Unexplained subfertility

    A couple is usually referred for investigation of subfertility after trying unsuccessfully to conceive for a year. Although many may despair of ever conceiving, the chance of successful spontaneous conception during the subsequent year is about 50%. However, the chance is reduced if the woman has never been pregnant (primary subfertility) or is aged over 30, or the duration of subfertility is longer than three years.

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    Unexplained subfertility can be a frustrating diagnosis for any couple trying to conceive

    Diagnosis of unexplained subfertility

    Unexplained subfertility is a diagnosis of exclusion. Up to 25% of patients who present for investigation in a reproductive medicine clinic are diagnosed with unexplained fertility. The diagnosis is usually made after investigations show normal semen parameters, ovulatory concentrations of serum progesterone in the mid-luteal phase, tubal patency, and a normal uterine cavity.

    A frustrating diagnosis for patients

    It is important to emphasise to couples with a diagnosis of unexplained subfertility that they have only had essential, simple fertility tests that do not always assess function. For example, despite showing tubal patency, normal transport of eggs and sperm in tubes has not been evaluated as no test for this is available. Although a woman may have an ovulatory concentration of serum progesterone and this indicates formation of a corpus luteum, it does not necessarily mean that an egg has been released nor that an egg has been picked up in the fallopian tubes. Even for women who ovulate, there is no information about oocyte quality and consequent embryo quality after fertilisation. Despite normal semen parameters, the sperm may …

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