This is a condition when a woman has 2 or more clinical pregnancy losses (miscarriages) before the pregnancies reach 20 weeks. Losses are classified by when they occur. Loss of a “clinical pregnancy” is diagnosed by a health-care provider using ultrasound. In most cases, a pregnancy can be seen with ultrasound as early as 5-6 weeks’ gestational age (or 1-2 weeks after a missed period). A “biochemical pregnancy” loss is one that has been detected only by urine or blood hormone testing before disappearing.
There are a variety of reasons why women may have more than one miscarriage:
Many early miscarriages (the ones that happen in the first 3 months of pregnancy) are due to genetic abnormalities in the embryo or fetus. Normally, there are 46 chromosomes that contain the genes for normal development. Many early miscarriages happen because the fetus has an extra chromosome or one is missing. For example, babies with Down syndrome have 47 chromosomes. Chromosome abnormalities occur for no known reason in up to 60% of first-trimester miscarriages. Genetic abnormalities typically do not allow development into a healthy baby. As women age, the miscarriage risk due to these genetic abnormalities increases — from 10%-15% in women younger than 35 years old to more than 50% in women over 40 years old.
A problem with the shape of the uterus might be a cause for pregnancy loss. Having a band of tissue inside the uterus, called a septum, can make the inside of the uterus too small. Women born with a septum may have more frequent miscarriages. Fibroids, benign muscle tumors of the uterus, are common. These can lead to miscarriages if they grow into or near the uterine cavity. Intrauterine adhesions can also cause miscarriages.
Smoking increases the risk for RPL. Using certain recreational drugs, such as cocaine, can also lead to miscarriage. Being overweight has been linked with RPL as well as other pregnancy complications. Excessive alcohol or caffeine intake might be linked with RPL.
Untreated medical conditions, such as thyroid disease or diabetes, can increase the risk for miscarriage. Abnormalities of the immune system or blood-clotting system (thrombophilia) can also cause RPL.
In over half of RPL cases, doctors cannot find the cause for losses. However, many of these may be due to genetic abnormalities.
Blood tests can show if a woman has certain medical, immune, or blood-clotting conditions that might cause RPL. The chromosomes of women and their male partners can be studied using a special blood test called a “karyotype.” Some healthy people have differences in the way their chromosomes are arranged. This can increase their risk for genetically imbalanced pregnancy losses. A special x-ray (hysterosalpingogram) or ultrasound (sonohysterogram) can show if a woman has a problem with the shape of her uterus. If available, the tissue from a miscarriage can be tested for genetic abnormalities.
With certain conditions, medical or surgical treatment can lower a woman’s risk for future miscarriage.
Surgery can fix some problems in the uterus, like extra tissue that divides the uterus (septum), some fibroids, or scar tissue. Correcting the shape of the inside of the uterus can often lower the chance for miscarriage. This can be done through hysteroscopy.
Women with autoimmune or clotting (thrombophilia) problems may be treated with low-dose aspirin and heparin. These medicines can be taken during pregnancy to lower the risk of miscarriage.
Recurrent pregnancy loss may be related to some medical problems. These include abnormal blood sugar levels, an over- or underactive thyroid gland, or high levels of the hormone prolactin. Treating medical conditions such as diabetes, thyroid dysfunction, or high prolactin levels can improve the chances of having a healthy, full-term pregnancy.
In about 5% of couples with RPL, one of the parents has a rearrangement (translocation) of their chromosomes. If one parent has a translocation, this can cause fetuses 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, it is recommended genetic counseling, IVF, and preimplantation genetic screening. This allows embryos without translocations to be chosen to increase the chance of a healthy pregnancy.
In general, whatever is healthy for a woman improves the chance of a healthy pregnancy. Stopping cigarette smoking and stopping illicit drug use (such as cocaine) will lower the risk for miscarriage. Limiting alcohol and caffeine intake may also help. Being overweight has been linked with increased risk of miscarriage, so healthy weight loss might also help pregnancy outcomes. There is no proof that stress, anxiety, or mild depression causes RPL.
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.
Even after having 3 miscarriages, a woman has a 60%-80% chance of conceiving and carrying a full- term pregnancy.
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