I'm not a Doctor, however, I can say this DID happen to me. It turned out that there was a 2nd fetus, which turned out to be (eventually) non viable too. If it hadn't happened t me...I wouldn't have believed it! Sometimes they continue to rise because the cells continue to divide even though there is no viable fetus. This happened to me. It basically means the gestational sac keeps growing, but there's no fetus in it.
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