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How Long Before You Know If You Are Having Twins or a Single Pregnancy?

If you have a family history of twins, you may be anxious to learn whether you’re carrying on the tradition. Dr. Hal Danzer, a reproductive endocrinologist and co-founder of Southern California Reproductive Center, says an ultrasound can detect twins at about six to eight weeks into gestation with about 90 percent accuracy. “At that point, you can get some indication of whether the twins are fraternal or identical by looking at the proximity of the gestational sac,” he explains. By 10 weeks into gestation, he states, you can know for certain if twins are identical or fraternal.

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