How are multiple pregnancies diagnosed?
Although previous generations often were surprised by a multiple birth, today most parents-to-be learn the news fairly early. A routine first-trimester ultrasound can detect most multiples.
(Sometimes a twin pregnancy that is identified very early is later found to have only one fetus. This is called "vanishing twin syndrome," and its cause is not well understood. The surviving twin generally is not harmed.)
Other factors can alert a health care provider that a woman may be expecting twins or more. These include:
- Rapid weight gain during the first trimester
- The uterus being larger than expected
- Severe pregnancy-related nausea and vomiting (morning sickness)
- More than one heartbeat heard by a provider using a hand-held ultrasound device (Doppler)
- More fetal movement than the woman experienced in a previous singleton pregnancy
- Abnormal results on maternal blood screening done around 16 weeks of pregnancy to screen for certain birth defects
A health care provider who suspects a multiple pregnancy most likely recommends that the woman have an ultrasound to find out for sure.
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