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J Ultrasound Med. 1989 Oct;8(10):561-3.

First trimester bradycardia. A sign of impending fetal loss.

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Department of Obstetrics and Gynecology, Brigham and Women's Hospital, Boston, Massachusetts.


Normal first trimester fetal heart rates rise from an average of 100 beats per minute (bpm) at 5 to 6 weeks to 140 bpm at 8 to 9 weeks. The heart rates of 65 consecutive first trimester fetuses between 5+ and 8+ weeks were measured to determine whether unusually slow first trimester fetal heartbeats are associated with a poor outcome. All five pregnancies in which heart rates were below 85 ended in spontaneous miscarriage. This study suggests that first trimester bradycardia may be associated with a poor prognosis for the pregnancy.

[Indexed for MEDLINE]

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