Miscarriage is the loss of a pregnancy in the first twenty weeks. About 15 to 20 per cent of known pregnancies end in miscarriage, and more than 80 per cent of these losses happen before twelve weeks.

The Causes

Between 50 and 70 per cent of first trimester miscarriages are thought to be random events caused by chromosomal abnormalities in the fertilized egg. Most often, this means that the egg or sperm had the wrong number of chromosomes, and as a result, the fertilized egg can’t develop normally.

In other cases, a miscarriage is caused by problems that occur during the delicate process of early development – for example, when an egg doesn’t implant properly in the uterus or an embryo has structural defects that don’t allow it to continue developing. Since most doctors don’t do a full-scale workup after a single miscarriage, it’s usually impossible to tell why the pregnancy was lost. And even when a detailed evaluation is performed – say after you’ve had two or three consecutive miscarriages – the cause still remains unknown in about half the cases.

When the fertilized egg has chromosomal problems, you may end up with what’s sometimes called a blighted ovum. In this case, the fertilized egg implants in the uterus and the placenta and gestational sac begin to develop, but the resulting embryo either stops developing very early or doesn’t form at all. Because the placenta begins to secrete hormones, you’ll get a positive pregnancy test and may have early pregnancy symptoms, but an ultrasound will show an empty gestational sac. In other cases, the embryo does develop for a little while but has abnormalities that make survival impossible, and development stops before the heart starts beating.

Once your baby has a heartbeat – usually visible on ultrasound at around 6 weeks – your odds of having a miscarriage drop significantly.

The Symptoms

Vaginal spotting or bleeding is usually the first sign of miscarriage. Keep in mind, though, that up to 1 in 4 pregnant women have some bleeding or spotting (finding spots of blood on your underpants) in early pregnancy, and half of these pregnancies don’t end in miscarriage.

You may also have abdominal pain, which usually begins after you first have some bleeding. It may feel crampy or persistent, mild or sharp, or may feel more like low back pain or pelvic pressure. If you have both bleeding and pain, the chances of your pregnancy continuing are much lower.

It’s very important to be aware that vaginal bleeding, spotting, or pain in early pregnancy can also signal an ectopic or a molar pregnancy. If you have any of these symptoms, call your doctor right away to determine whether you have a potential problem that needs to be dealt immediately.

Also, if your blood is Rh-negative, you may need a shot of Rh immune globulin within two or three days after you first notice bleeding, unless the baby’s father is Rh-negative as well.

Some miscarriages are first suspected during a routine prenatal visit, when the doctor can’t hear the baby’s heartbeat or notice that your uterus isn’t growing as it should be (Often the embryo or fetus stops developing a few weeks before you have symptoms, like bleeding or cramping). If your practitioner suspects that you’ve had a miscarriage, she’ll order an ultrasound to see what’s going on in your uterus and possibly do a blood test.

Miscarriage – The Risk Factors

Though any woman can miscarry, some are more likely to miscarry than others. Here are the most common risk factors:

• Age: Older women are more likely to conceive babies with chromosomal abnormalities, and to miscarry them as a result. In fact, 40-year-olds are about twice as likely to miscarry as 20-year-olds.
• History of miscarriages:Women who have had two or more miscarriages in a row are more likely than other women to miscarry again
• Chronic diseases or disorders:Poorly controlled diabetes, certain inherited blood clotting disorders, certain autoimmune disorders and certain hormonal disorders
• Uterine or cervical problems:Having certain uterine abnormalities or a weak or abnormally short cervix known as cervical insufficiency.
• History of birth defects or genetic problems:Having had a child with a birth defect, or a family history of genetic problems.
• Certain infections:Research has shown a somewhat higher risk for miscarriage if you have listeria, mumps, rubella, measles, cytomegalovirus, parvovirus, gonorrhea, HIV, and certain other infections
• Smoking, drinking, and drugs:Smoking a lot, drinking too much alcohol, and using drugs like cocaine and ecstasy during pregnancy can all increase your risk for miscarriage. And some studies show that drinking four or more cups of coffee a day and a higher can trigger a miscarriage.
• Taking certain medications:Some medications have been linked to increased risk of miscarriage. It’s important to ask your doctor about the safety of any medications you’re taking even while you’re trying to conceive.
• Exposure to environmental toxins:Environmental factors that might increase your risk include lead; arsenic; some chemicals, like formaldehyde, benzene and ethylene oxide; and large doses of radiation or anesthetic gases.
• Paternal factors:Little is known about how the father’s condition may contribute to a couple’s risk for miscarriage, though the risk increases with the father’s age. Researchers are studying the extent to which sperm could be damaged by environmental toxins but still manage to fertilize an egg.

Your risk of miscarriage also increases with each child you bear and if you get pregnant within three months after giving birth.