A high proportion of pregnancies may fail to develop and end in miscarriage. The are several causes that might lead to a miscarriage and, depending on the cause, several prevention methods
A miscarriage is usually a traumatic experience, more so if the failed pregnancy is the product of an infertility treatment. The satisfaction of a positive pregnancy test is followed by frustration and sadness caused by the miscarriage. Fifteen to twenty per cent (15 – 20%) of all pregnancies, conceived naturally or by assisted reproduction techniques, end in miscarriage, 75% of which occur in the first 12 weeks of pregnancy.
Common miscarriage causes:
- Chromosomal abnormality: Abnormalities in the structure or number of the chromosomes of the embryo, very often end in miscarriage. A study showed that up to 70% of all miscarriages in the first trimester of pregnancy are caused by chromosome anomalies .
- Thrombophilia: Thrombophilia may affect all stages of pregnancy by causing clots in the placenta leading to intrauterine fetal death. Women with a history of one miscarriage or intrauterine death, or a family history of thrombphilia should get the suitable blood tests for thrombophilia screening.
- Hormonal level disorders: It is possible that disorders in the levels of hormones may cause miscarriage because the endometrium is not sufficiently developed to accept and successfully keep the fertilized egg. Women with thyroid and adrenal glands disorder, as well as women with diabetes face a greater risk of miscarriage. In addition, the elevated levels of prolactin may prohibit the normal development of the endometrium.
- Anatomical (structural) anomalies: Uterine anatomical anomalies may cause miscarriage, usually because the implantation of the fertilized egg is prevented by this anomaly. Uterine fibroids are benign tumours on the uterine wall. Fibroids may cause infertility if they block the openings of the tubes or if their positions prevent the endometrium to function normally.
- Cervical disorders: Another cause for miscarriage of the second trimester is the incompetence of the cervix to remain closed as it is pressed by the weight of the developing embryo.
- Infections: It is possible that infections like rubella, herpes, chlamydia, ureoplasma, cytomegalovirus may, in some cases, affect the development of the embryo and cause miscarriage.
- Environmental factors: Toxins carried by the air may also cause damage to the embryo or a miscarriage, especially if the mother is exposed to them often from the 20th week of the pregnancy and onwards. A few studies showed that the use of marijuana, tobacco, caffeine and alcohol might also affect the development of the embryo and lead to miscarriage. Women are advised to avoid or restrict these substances during pregnancy.
- Immunological factors: The antiphospholipidic antibodies may cause miscarriage. Blood tests may detect the presence of these antibodies. Anticoagulant medicines like heparin or aspirin may be used for the thinning of blood. Antipaternal antibodies are another cause of miscarriage. Treatment with paternal lymphocytes is believed to help considerably.
Some, but not all, women experience a few symptoms before the miscarriage, like a dark brown, light pink or red blood vaginal discharge, decrease of the breast tenderness or size, absence of embryo movement or his cardiac pulse. Pain and heavy vaginal bleeding indicate that a miscarriage is in progress. It is imperative that the doctor should be notified immediately. Examination of the miscarried tissue may aid in the determination of the cause(s) of the miscarriage.
1: Fritz B, Hallermann C, Olert J, Fuchs B, Bruns M, Aslan M, Schmidt S, Coerdt W, Müntefering H, Rehder H. 2001. Cytogenetic analyses of culture failures by comparative genomic hybridisation (CGH)-Re-evaluation of chromosome aberration rates in early spontaneous abortions. Eur J Hum Genet. 9(7): 539-547.