Below is the research I found from babycenter.com about miscarriage which I think most of us as a women should know...
What is a miscarriage?
Miscarriage is the loss of a pregnancy in the first 20 weeks. About 15 to 20 percent of known pregnancies end in miscarriage, and more than 80 percent of these losses happen before 12 weeks. This doesn't include situations in which you lose a fertilized egg before you get a positive pregnancy test. Studies have found that 30 to 50 percent of fertilized eggs are lost before a woman finds out she's pregnant, because they happen so early that she goes on to get her period about on time. If you lose a baby after 20 weeks of pregnancy, it's called a stillbirth.
What causes a miscarriage?
Between 50 and 70 percent 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 healthcare practitioners won'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 of cases.When the fertilized egg has chromosomal problems, you may end up with what's sometimes called a blighted ovum (now usually referred to in medical circles as an early pregnancy failure). 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.
What kinds of things might put me at a higher risk for miscarriage?
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.
• A history of miscarriages: Women who have had two or more miscarriages in a row are more likely than other women to miscarry again.
• Certain chronic diseases or disorders: Poorly controlled diabetes, certain inherited blood clotting disorders, certain autoimmune disorders (such as antiphosphilipid syndrome or lupus), and certain hormonal disorders (such as polycystic ovary syndrome).
• Uterine or cervical problems: Having certain uterine abnormalities or a weak or abnormally short cervix (known as cervical insufficiency).
• A history of birth defects or genetic problems: Having had a child with a birth defect, or a family history (or a partner with 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 using 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 an association between drinking four or more cups of coffee a day and a higher risk of miscarriage.
• Taking certain medications: Some medications have been linked to increased risk of miscarriage, so it's important to ask your caregiver about the safety of any medications you're taking even while you're trying to conceive. This goes for prescription and over-the-counter drugs, including nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and aspirin.
• 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. Some studies have found a greater risk of miscarriage when the father has been exposed to mercury, lead, and some industrial chemicals and pesticides.Your risk of miscarriage also rises with each child you bear and if you get pregnant within three months after giving birth.
• 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.
• A history of miscarriages: Women who have had two or more miscarriages in a row are more likely than other women to miscarry again.
• Certain chronic diseases or disorders: Poorly controlled diabetes, certain inherited blood clotting disorders, certain autoimmune disorders (such as antiphosphilipid syndrome or lupus), and certain hormonal disorders (such as polycystic ovary syndrome).
• Uterine or cervical problems: Having certain uterine abnormalities or a weak or abnormally short cervix (known as cervical insufficiency).
• A history of birth defects or genetic problems: Having had a child with a birth defect, or a family history (or a partner with 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 using 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 an association between drinking four or more cups of coffee a day and a higher risk of miscarriage.
• Taking certain medications: Some medications have been linked to increased risk of miscarriage, so it's important to ask your caregiver about the safety of any medications you're taking even while you're trying to conceive. This goes for prescription and over-the-counter drugs, including nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and aspirin.
• 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. Some studies have found a greater risk of miscarriage when the father has been exposed to mercury, lead, and some industrial chemicals and pesticides.Your risk of miscarriage also rises with each child you bear and if you get pregnant within three months after giving birth.
There are more found from this link http://www.babycenter.com/0_understanding-miscarriage_252.bc?page=1&articleId=252
