Among all clinically detected pregnancies, 15% end in spontaneous abortion. This rate may increase up to 40% in patients with the history of two or more abortions. Recurrent abortion is clasically defined as loss of three or more early pregnancies. However, two abortions of pregnancies obtained with treatment in infertile patients require diagnostic work-up. Prevalence of recurrent abortions is 0.5-1% in the population. Recurrent abortions may be due to anatomical, genetical, hormonal, environmental problem sor due to coagulation disorders. Congenital defects of the uterus, myoma uteri and polyps and intrauterine adhesions may also be responsible for recurrent abortions.
These defects may be diagnosed by ultrasonography or hysteroscopy and corrected surgically. In more than half of early pregnancy losses, the problem is genetical abnormalities. Most genetical problems are not herited from the parents but occur during the formation of the zygote. But, genetical problems account only for 2-4% of recurrent abortions.
Balanced translocations are the most common genetical problems followed by microdeletions, Robertsonian translocations and structural chromosomal defects. These defects are more common in pregnancies obtained in couples with male infertility. Genetical analysis of the abortus material can be useful for the diagnosis. PGD may be used before embryo transfer to eliminate these genetical problems but its efficacy has not been proved to make PGD a routine part of IVF.
There are some hormonal problems affecting implantation. Uncontrolled diabetes, thyroid disorders, elevated prolactin levels may result in recurrent pregnancy losses. Recuurrent pregnancy loss is a common finding in PCOS patients and this may be due to elevated androgen levels.
Paternal antigens of the embryo have been thought to be considered as strange by the maternal immune system and several immunologic adaptations take place in the mother during a pregnancy. For instance, trophoblasts may not produce MHC II antigens or paternal antigens may be covered by blocking antigens to prevent their recognition as strange by the maternal immune system. Some of these substancec are useful for the pregnancy Th2, Il-3, Il-4, Il-5, Il-10, Il-13) and some of them are harmful (Th1, TNF-alpha, TNF-beta, gamma-interferon, Il-2). Especially, Th1 cytokines are thought to have a direct deleterious effect on the placenta. Although “natural killer cell” concentration has been found in increased amounts among women with recurrent pregnancy losses, the net effect of this finding has not been proved. In brief, many alterations and adaptations in the immune system occur during early pregnancy and any role of the immune system in recurrent abortions is controversial. Lymphocyte vaccines and IVIG treatments are mostly experimental and their efficacies have not been proved. Their routine use is not recommended.
Coagulation and fibrinolysis are simultaneous events in the human body and they are balanced. This balance prevents thrombosis or bleeding. Thrombosis during pregnancy may affect the placenta and result in recurrent abortions. Among congenital defects are factor V Leiden mutation, prothrombin gene mutation and hyperhomocystinemia. Rarer defects are protein C, protein S and antithrombin III deficiencies.
Another hypercoagulation syndrome is antiphospholipid syndrome (APLs). APLs goes with recurrent abortions, intrauterine growth retardation and preterm birth. Once the diagnosis is established, treatment with heparin is required.
Infectious agents are very rare causes of recurrent abortions.
Too much weight or very few body weight may also be causative agents in recurrent abortions. Women whose body mass index is not within 19 – 25 kg/m2 should achieve a normal body weight via a balanced and folic acid supplemented diet and then get pregnant. Smoking, caffein and alcohol should be avoided.
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