Any couple who has suffered a miscarriage may have a definable and treatable cause for pregnancy loss. However, studies have shown that pregnancy loss does occur in up to 15 percent of all pregnancies. The vast majority are related to the quality and genetic composition of the egg. Perhaps in 10 percent, the sperm is the causing factor.
Usually infertility testing for pregnancy loss is started after two to three pregnancy losses.The decision to pursue an evaluation should be based on the couple’s age, the number of miscarriages they have had, if they have a family history of recurrent miscarriages, or known risk factor for recurrent pregnancy loss.
Causes of pregnancy loss are divided into the categories of anatomic, chromosomal, immunologic, infectious, and unknown.
The anatomic causes of pregnancy loss include abnormalities of the uterus and cervix. If the uterus contains a septum (or wall) within its cavity, there may be a risk particularly for late miscarriage. In addition, uterine fibroids or scarring can also cause pregnancy loss. This condition is amenable to surgical correction with a dramatic increase in the likelihood of carrying a pregnancy.
In patients with anatomic causes for pregnancy loss, surgical correction offers a vastly improved prognosis. For example, if a patient has a uterine septum, her chances of having a miscarriage without therapy is 70 percent. Once her septum is corrected, however, her chance of miscarriage returns to that of the unaffected population.
If one or both of the prospective parents carry a chromosomal abnormality, this may be passed on to a developing fetus and cause pregnancy loss. These abnormalities will not show up in the parents and are only diagnosed by blood examination with a chromosome analysis (karyotype). While not correctable, finding any chromosome abnormalities in one or both prospective parents will allow for genetic counseling and accurate assessment of the chances of having a successful pregnancy. Through IVF, healthy embryos can then be selected.
Immunologic causes of pregnancy loss include the presence of certain antibodies. Some of the most important of these and other abnormalities are involved in abnormal clotting of the blood vessels to the pregnancy. These are classed as thrombophilias. The antibodies are shared with rheumatologic disease such as lupus and rheumatoid arthritis. The role of these factors in pregnancy loss is unclear in some cases and at times controversial.
There is evidence that treatment with low-dose aspirin and heparin may improve pregnancy outcomes in women with these antibodies. Heparin, aspirin, and steroid therapy for autoimmune factors have approximately 60 percent likelihood in successful pregnancy outcome.
Certain cervical and uterine infections may increase the likelihood of pregnancy loss. These are easily diagnosed with a cervical culture and easily treated with oral antibiotics.
Unknown pregnancy loss – miscarriage with no identifiable cause – accounts for approximately 50 percent of couples who have a history of two or more pregnancy losses. If no cause can be found, then none should be treated.
Research on pregnancy loss would support this as patients in this group have approximately a 60- to 70-percent likelihood of a successful next pregnancy. In other words, a failure to find a pregnancy loss cause does not imply a hopeless situation. In fact, patients without a known cause of pregnancy loss have overall an excellent outcome.