It’s very unlikely you’ll ever know the actual cause of a one-off miscarriage, but most are due to the following issues:
• Abnormal fetus
The most common cause of miscarriage in the first few months is a one-off malformation of the fetus, often due to chromosomal abnormalities. “It’s not like the baby is fine one minute and suddenly dies the next,” says Professor James Walker, professor of obstetrics and gynecology at the University of Leeds.
“These pregnancies fail from the start and were never destined to succeed.” Most miscarriages like this occur after eight weeks, although bleeding may not start until three or four weeks later, which is important to consider in later pregnancies. “If a scan shows a healthy heartbeat at eight weeks, you have a 95 percent chance of a successful pregnancy,” says Professor Walker.
• HORMONAL FACTORS
A hormonal imbalance could cause an intermittent miscarriage and never be a problem again. However, a small number of women with long cycles and irregular periods may experience repeated miscarriages because the lining of the uterus is too thin, making implantation difficult.
Unfortunately, hormone treatment is not very successful.
‘There used to be a trend towards treatment with progesterone, but studies show that it really doesn’t work,’ warns Professor Walker. “There is some evidence that injections of HCG (human chorionic gonadotropin, a hormone released in early pregnancy) may help, but it’s not the answer for everyone.” Treatment must be started as soon as pregnancy is confirmed, around four or five weeks.
For women over 40, one in four women who become pregnant will have a miscarriage. [One in four women of all ages miscarry, but these figures include women who don’t know that they are pregnant. Of women who do know that they’re pregnant, the figure is one in six. Once you’re over 40, and know that you’re pregnant, the figure rises to one in four]
• AUTOIMMUNE BLOOD DISORDERS
About 20 percent of recurrent miscarriages are from lupus, or a similar autoimmune disease that causes blood clots to form in the developing placenta.
A simple blood test, which may need to be repeated several times, can reveal whether or not this is the problem. “A negative test does not mean a woman is doing well,” warns Mr Roy Farquharson, consultant gynecologist who runs an early pregnancy unit at Liverpool Women’s Hospital.
Pregnancy can often be a trigger for these disorders, so testing should be done as soon as possible,” he adds. But it can be easily treated with low-dose aspirin or heparin injections, which help thin the blood and prevent clots from forming — a recent study also showed that women do equally well on both. “We have a 70 percent live birth rate in women treated for these disorders,” says Dr. Farquharson, “which is excellent.”
• OTHER CAUSES
During abnormalities of the uterus, such as B. fibroids, can cause a miscarriage, many women have no problem carrying the pregnancy to term. An incompetent cervix can also lead to miscarriage after about 20 weeks.
While this can be treated with a special stitch in the cervix, studies suggest this isn’t particularly effective, although it can delay labor by a few weeks. Gene and chromosomal abnormalities, which can be detected by blood tests, can also cause recurrent miscarriages in a small number of couples.
A procedure known as preimplantation genetic testing can help. After in vitro fertilization (IVF), a single cell is removed from the developing embryo and examined for the genetic defect. Only healthy embryos are then replaced in the womb.
It’s an expensive and stressful procedure — and pregnancy rates are usually quite low — but for some, it’s preferable to repeated miscarriages or a genetically abnormal baby.