When a biochemical pregnancy does not lead to a viable pregnancy, the woman often feels a failure. If more than one miscarriage occurs it can be a huge disappointment, especially if there are no obvious causes.

Even though the focus is usually on the woman, it is far from always that the cause can be found there.
The man may have normal sperm quality, but one likely cause is a problem with the sperm DNA fragmentation.

Causes in the woman

The first weeks of pregnancy are a critical phase where many things need to fall into place for the foetus to develop normally. Changes in the fetus may mean that it is not viable. Chromosomal errors are a frequent cause.
In the woman, changes in the uterus, blood coagulation, infection or disturbances in metabolism may result in a miscarriage. In 10 to 30% of the normal pregnancies, the woman develops antibodies against the part of the fetus which originates from the father. Such antibodies may result in a miscarriage. One of the more recent explanations which now is the microbiome in the intestine, the vagina and the uterus.
Several couples experience 3 or more miscarriages. This is called ‘repeated pregnancy loss’.

Causes in the male

The semen quality is usually fairly normal, when a couple is able to conceive naturally. Up to recently, the man has not been suspected in cases of a miscarriage or repeated pregnancy loss. But this is now changed as normal semen quality does not exclude that the sperm DNA may be fragile or damaged. In addition, several scientific studies the past couple of decades have showed that the man may play a very important role.

A large study of data from couples who had experienced one or several miscarriages showed that both increasing age of the woman and of the man increased the risk. In the woman, it is well known that the risk of chromosomal errors (aneuploidy) increases as the woman gets older. However, chromosomal errors in sperm are very rare.

Sperm DNA fragmentation is a frequent cause
Research in the men now shows that poor sperm DNA integrity is a very common cause of miscarriages. The fragile DNA becomes fragmented before the fertilization of the oocyte is completed. Incomplete repair of the DNA in the oocyte results in spelling errors (mutations) which means that the embryo/fetus is not viable. Data obtained with the SDI®-test for 263 couples with repeated miscarriages show that 37.3% had a DFI above 15.

Investigation of miscarriage/repeated pregnancy loss

Sperm DNA fragmentation was already recognized as an important factor for miscarriage in 2017. As a result of this, the European Society for Human Reproduction and Embryology (ESHRE) recommended that testing of sperm DNA integrity was included in the investigation of miscarriage or repeated pregnancy loss.