Recurrent miscarriage is probably one of the most frustrating events for a couple undergoing fertility treatment.

The overall percentage of pregnancies that end in miscarriage lies around 15% being one of the most common complications in pregnant women.

Recurrent miscarriage is defined as two or more consecutive spontaneous pregnancy losses. Even if the miscarriages can just be bad luck it is strongly recommended to conduct a number of test on both partners as chances are high that there is something causing it.

After several consecutive miscarriages it is very likely that there is something wrong and therefore the risk of a pregnancy loss happening again is high.

Recurrent miscarriage investigations on the couple should include a hysterosalpingogram, hysteroscopy in some cases, karyotype on both partners, meiosis study on the male (on the sperm or by means of a testicular biopsy), endometrial biopsy, blood test to check hormonal levels, infectious disease screening and antiphospholipid antibodies investigations.

There are several causes of recurrent miscarriage:

Chromosomal abnormalities
Around 60% of spontaneous miscarriages occurring during the first three months of pregnancy have chromosomal abnormalities.
Generally the sooner it happens, the likeliest it is that embryos are chromosomally abnormal.

There are basically two situations that can result in abnormal embryos:

• One of the partners is carrier of a balanced chromosomal abnormality (e.g. a translocation). This condition can be detected with a karyotype.
• The chromosomal pattern of cells is normal but the gamete development (eggs or sperm) is irregular. This condition can only be detected on the male. 

Both situations will result in chromosomally abnormal gametes and therefore abnormal embryos.

Uterine anatomical abnormalities
Cervical incompotence and congenital abnormalities such as a uterine septum are often associated with recurrent miscarriages. Other problems that may adversely affect the pregnancy are adhesions in the uterine cavity, fibroids and endometrial polyps.  

Hormonal factors
In some cases recurrent miscarriages can be caused by hormonal problems including luteal phase insufficiency, polycystic ovarian syndrome, elevated levels of prolactin, diabetes mellitus and severe thyroid disorders.

Infections
There is controversy about the role of infectious agents in relation to recurrent miscarriages. These agents could be identified in the embryo or in the fetus, in placenta tissue or in the endometrium.

Immunological factors
In some cases there is an autoimmune factor involved in the miscarriages due to the presence of antiphospholipid antibodies.

Clotting factors
The tendency to form blood clots too easily due to reduced antithrombine levels (clotting agents that prevent blood clots) may cause recurrent miscarriages.

Environmental factors

The toxicity of heavy metals or the exposure to radiations has been associated with pregnancy loss. Smoking and drinking may also increase the risk of miscarriage.

There are multiple causes responsible for recurrent abortion.

There is controversy surrounding the participation of infectious agents as possible factors causing recurrent abortion.