Last reviewed 01/2018

In around 50% of recurrent miscarriages a cause cannot be identified and is termed as idiopathic (1). Other p ossible causes of recurrent abortion include:

  • chromosome abnormalities in either parent (seen in around 3–5% of couples with recurrent miscarriage) (2)

  • uterine abnormalities

  • infection – bacterial vaginosis has been widely regarded as a cause (Rubella, Toxoplasmosis, Listeria and Parvovirus do not cause recurrent miscarriages) (3)
  • serious chronic disease e.g. syphilis, renal disease, diabetes, and hypothyroidism

  • antiphospholipid syndrome - up to 20% of cases of recurrent miscarriage have this syndrome (1)

  • cervical incompetence

  • mistaken diagnosis - for example delayed periods in a woman trying to become pregnant

  • polycystic ovarian syndrome: 58 % of patients with recurrent miscarriages have ultrasound diagnosed PCOD. Raised LH before conception may therefore indicate an increased risk of miscarriage.

  • smoking - increases miscarriage rates

  • idiopathic - the majority of cases, a cause is found only in a few percent

Although the main cause of sporadic miscarriage is foetal chromosomal abnormality, patients with repeated losses tend to miscarry foetuses that are chromosomally normal. Balanced chromosomal translocations occur in no more than 1 in 10 couples.