A multiple pregnancy is defined by the March of Dimes as carrying more than one baby at the same time. Most pregnancies in the United States are singletons, with only one baby in utero. Approximately 3 percent of American births are multiple pregnancies; most are in twins with just a fraction resulting in higher order multiples. Past generations of women may not have been able to tell that they were carrying more than one baby. Technology has played a role in diagnosing a multiple pregnancy.
Belly Size
One sign of a multiple pregnancy is that the mother-to-be grows more quickly than is expected with a singleton pregnancy. The uterus expands earlier to accommodate two babies and may at first cause a woman to rethink the dates of her last menstrual period and possible conception date. She might notice that she is gaining a significant amount of weight during the first trimester, in order to support two babies, explains the American Pregnancy Association.
Hormone Levels
Hormone levels may point to the fact that a multiple pregnancy is underway. Human chorionic gonadotropin (hCG) is a hormone produced by the body from very early on in pregnancy. In the first few days and weeks after conception, hCG levels rise exponentially. When two or more babies share the uterus, the hormones levels increase even more than in a normal singleton gestation. HCG is measured through a blood test and may be used as to help diagnose a multiple pregnancy.
Heightened Symptoms
Breast tenderness, nausea and mood swings are all symptoms that some women experience when they are pregnant. Carrying more than one baby can make these symptoms intensify. Severe morning sickness is not unusual but may be more likely in a woman who is pregnant with twins, triplets or higher order multiples.
Double Vital Signs
Seeing two occupied sacs on an ultrasound or hearing two distinct heartbeats during an examination is a sign of a multiple pregnancy. Some multiples may be noticed very early on in the pregnancy before an ultrasound is performed. Doctors who suspect that a woman may be carrying multiples due to size discrepancies, an increase of nausea or the use of fertility drugs will order an ultrasound. Imaging technology can provide a definitive answer about the numbers of babies in the womb.
False Positive Screening Results
Around the sixteenth week of pregnancy, women can elect to have testing done to identify the risk of possible birth defects. Testing includes amniocentesis, chorionic villus sampling and alpha-fetoprotein. Abnormal results of any of these tests may occur when, in fact, there are no problems with the developing child. Sometimes these results, referred to as false positives, can indicate a multiple pregnancy.
