OMAHA, Neb. -- Studies find 20 percent of pregnancies end in miscarriage, and although the number may seem high, some doctors say it is a sign of the times.

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One reason for the high number of reported miscarriages could be over-the-counter pregnancy tests. Women are finding out earlier than ever they are pregnant -- many times before eight to 10 weeks into pregnancy, reported television station KETV in Omaha.

Dr. Teresa Berg, of the Nebraska Medical Center in Omaha, said it is not uncommon for a positive pregnancy test to occur before the fertilization process is complete.

"There is a perception that there are more miscarriages now than there were 20 to 30 years ago, but likely there's probably not a greater number, just that early detection," Berg said.

Most times it's not anyone's fault that a miscarriage happened, Berg said, but women are more likely to miscarry if they smoke, drink more than four cups of coffee a day, take anti-inflammatory painkillers such as aspirin or ibuprofen, or are over 40.

Physicians also recommend that women take a daily prenatal vitamin containing folic acid if they are trying to get pregnant.