When should recurrent miscarriage be investigated?

The current RCOG definition of recurrent miscarriage is three or more first-trimester miscarriages. They do not have to be consecutive, and healthy pregnancies in between do not erase the history.

But RCOG also specifically advises doctors to use clinical discretion and consider more extensive evaluation after two first-trimester miscarriages when there is reason to suspect a pathological rather than purely sporadic cause.

European guidance defines recurrent pregnancy loss as two or more pregnancy losses.

Earlier discussion may be sensible when there are other reasons for concern, for example:

• increasing maternal age, when time itself matters;
• two miscarriages with a concerning or similar pattern;
• a previous second-trimester miscarriage;
• known or suspected uterine abnormality;
• a medical or family history that raises concern;
• difficulty conceiving as well as repeated pregnancy loss.

This does not mean that every woman needs a large panel of tests after one miscarriage. It means the decision should be individual rather than simply determined by a number.

Depending on your history, assessment may include:

• a detailed pregnancy, medical and family history;
• pelvic ultrasound to assess the uterus and uterine cavity;
• blood tests for antiphospholipid syndrome (APS);
• thyroid function, including thyroid antibodies where appropriate;
• other blood tests when the medical history suggests a reason, such as diabetes or particular hormonal problems;
• genetic assessment in selected circumstances.

Not every test is needed for every woman.

APS is diagnosed using specific antiphospholipid antibody blood tests together with the appropriate clinical history. A single positive blood test is not enough to confirm APS. The tests need to be positive on two occasions at least 12 weeks apart, and testing after a miscarriage needs to be appropriately timed. If APS is confirmed, treatment in a future pregnancy may improve the chance of a successful outcome.

Routine broad screening for inherited thrombophilias is not recommended for every woman with recurrent early miscarriage. Likewise, many commercially offered immune, natural-killer-cell and other specialised tests have not been shown to be useful as routine investigations. A good recurrent-miscarriage assessment is not measured by the number of tubes of blood taken.

Chromosomal abnormalities in an embryo are a major cause of miscarriage. Testing pregnancy tissue may sometimes help explain an individual loss, particularly in the setting of recurrent miscarriage, but it is not routinely required in every case. Chromosome testing of both partners may be considered when the history or pregnancy-tissue result suggests it, rather than being automatic for everyone.

Many cases of recurrent miscarriage remain unexplained even after appropriate assessment. This can feel unsatisfactory, but a normal work-up is not the same as a hopeless prognosis. Your chance of a future successful pregnancy depends particularly on your age and previous pregnancy history, and many women with unexplained recurrent miscarriage will subsequently have a successful pregnancy. Support and access to early pregnancy care in a future pregnancy are also important.

If you have had three early miscarriages, investigation is clearly appropriate. If you have had two, it is reasonable to ask whether your particular history justifies starting earlier.

And after one miscarriage, you can still ask questions — especially if there was something unusual about the pregnancy or your medical history.

The useful question is not:

“Have I earned the right to be investigated yet?”

It is:

“Given my history, is there anything sensible we should look for now?”