Known causes of Recurrent Miscarriage:

Antiphospholipid syndrome (APS)

  • This blood clotting problem is the most important treatable cause of recurrent miscarriage. It happens when your immune system makes abnormal antibodies that attack fats called phospholipids in your blood.
  • This makes the blood more ‘sticky’ and likely to clot, which is why APS is sometimes called ‘sticky blood syndrome’.
  • It is also known as ‘Hughes syndrome’ after the expert who named it. It is not clear why these antibodies cause miscarriage.
  • They may stop the pregnancy embedding properly in the uterus (womb); or they may interfere with blood flow to the placenta, which supports the baby. 
  • APS can also lead to problems in later pregnancy, including the baby not growing enough, pre-eclampsia or stillbirth.

Other blood clotting problems

Some inherited blood clotting disorders can cause recurrent miscarriage, particularly after 14 weeks. These include:

  • Factor V Leiden
  • Factor II (prothrombin)
  • Gene mutation
  • Protein S deficiency

Abnormal chromosomes

  •  The chromosomes in every cell of your body carry hereditary information in the form of genes.
  • Everyone has 23 pairs of chromosomes, and 22 of these are the same in men and women. The 23rd pair is different because they determine gender.
  • Men normally have one X and one Y chromosome and women two X chromosomes.
  • A baby inherits half its chromosomes from each parent.
  • About half of all miscarriages happen because the baby’s chromosomes are abnormal. This is not usually an inherited problem: it happens when the egg and sperm meet or soon after the egg is fertilised.
  • The older you are the more likely this is to happen. Much less commonly (in less than five in one hundred couples with recurrent miscarriage), one partner carries a chromosomal defect called a ‘balanced translocation’. This doesn’t cause a problem for the parent, but it can be passed on to the baby as an ‘unbalanced translocation’.
  • This means that some genetic information is duplicated and some is missing.

Cervical weakness

  • It is also known as ‘incompetent cervix’
  • Some women, probably less than one in a hundred, have a weakness in the cervix that allows it to dilate too early.
  • This is a known cause of late (second trimester) miscarriage.