Recurrent pregnancy loss is a condition when a woman has two or more clinical pregnancy losses (miscarriages) before 20 weeks of gestation. A clinical pregnancy loss occurs after a pregnancy has been visualized on an ultrasound examination and can occur as early as 5-6 weeks’ gestation (1-2 weeks after a missed period). A “biochemical pregnancy” occurs when a urine or blood pregnancy test is found to be positive but declines and becomes negative before a clinical pregnancy can be seen on ultrasound. Biochemical losses are not usually included in making a recurrent pregnancy loss diagnosis.
There are a variety of reasons why women may have recurrent pregnancy loss:
Many early miscarriages (the ones that happen in the first 3 months of pregnancy) are due to genetic abnormalities in the embryo. There are 46 chromosomes in a normal embryo. When the embryo has an extra chromosome or one is missing, the pregnancy is likely to end in miscarriage. Chromosome abnormalities occur in up to 60% of first-trimester miscarriages. Such genetic abnormalities typically do not allow development into a healthy baby. The risk of miscarriage due to these genetic abnormalities increases from 10%-15% in women younger than 35 to more than 50% in women older than 40.
In about 5% of couples with recurrent pregnancy loss, one of the parents has a rearrangement (translocation) of their chromosomes. If one parent has a translocation, this can result in embryos with chromosome imbalances that are more likely to miscarry. The parents’ blood can be studied (karyotyped) to see if they have a translocation. If a chromosomal problem is found, the doctor might recommend genetic counseling. While many couples with translocations eventually conceive a healthy pregnancy naturally, your doctor might suggest fertility treatments, such as in vitro fertilization (IVF).
Abnormalities of the uterus may also be a cause of pregnancy loss. Some of these are congenital (the woman is born with it) such as a uterine septum. In such cases there is a fibrous septum extending down into the uterine cavity, which may adversely affect implantation or development of the embryo. Women born with a uterine septum may have more frequent miscarriages.
Fibroids (benign muscle tumors of the uterus) are very common and may lead to miscarriages if they grow into or near the uterine cavity.
Surgery can be performed in many cases of uterine abnormalities including removal of a septum, fibroid or scar tissue. Correcting the shape of the inside of the uterus can often lower the chance for miscarriage. The surgeon uses a tool with a camera (hysteroscope) passed through the vagina to repair the inside of the uterus. The patient goes home the same day and recovery time is a few days to a week.
Untreated medical conditions, such as thyroid disease or diabetes, can increase the risk for miscarriage. Treating medical conditions such as diabetes, thyroid dysfunction, or high prolactin levels can improve the chances of having a healthy, full-term pregnancy. Abnormalities of the immune system or blood-clotting system (thrombophilia) can also cause recurrent pregnancy loss. Women with autoimmune or clotting problems may be treated with low-dose aspirin and heparin. These medicines can be taken during pregnancy to lower the risk of miscarriage.
Stopping cigarette smoking and stopping illicit drug use will lower the risk for miscarriage. Limiting alcohol and caffeine intake may also be helpful. Obesity or being overweight has been linked with increased risk of miscarriage, so healthy weight loss might also help pregnancy outcomes. There is no clear scientific proof that stress, anxiety, or mild depression causes recurrent pregnancy loss. However, these are important problems that are common in women with recurrent pregnancy loss. Psychological support and counseling can help couples cope with the emotional pain of miscarriage and create a healthy environment for a pregnancy.
There is no proof that intravenous (IV) infusions of blood products (such as intravenous immunoglobulin [IVIG]) or medicines (such as soybean oil infusion) decrease the risk of miscarriage.
In over half of recurrent pregnancy loss cases, doctors cannot find the cause for losses. However, many of these may be due to genetic abnormalities. Even after having 3 miscarriages, a woman has a 60%-80% chance of conceiving and carrying a full-term pregnancy.