A mother's lifestyle also can increase her risk of a first-trimester miscarriage. Studies suggest that women who have two or more alcoholic drinks a day double their risk of miscarriage. Women who smoke cigarettes have a 20 to 80 percent greater risk of miscarriage than nonsmokers. Chromosomal abnormalities appear to cause up to 20 percent of second-trimester miscarriages. Certain immune system problems also can cause these losses.
Doctors usually perform no tests fol-lowing a first miscarriage that occurs in the first trimester.
The cause of these early losses is often unknown. Some doctors now recommend that the tissue be tested to confirm that a chromosomal abnormality caused the miscarriage. If a woman has a miscarriage in the second trimester, doctors often are able to determine the cause. Her doctor may recommend some tests, including blood tests, to discover the cause of the loss. While miscarriage is usually a one-time occurrence, up to one in twenty couples experience two miscarriages in a row, and one in one hundred have three or more.