How Early Can Fetal Heart Pulsations Be Detected Reliably Using Modern Ultrasound Equipment?

摘要

Background: Current national guidelines for the use of ultrasound in early pregnancy state that the embryonic heartbeat should be identified when the embryo measures 6 mm in length (RCOG/RCR 1995). Failure to visualise heart pulsations in embryos measuring 6 mm or less requires patients to wait 7 days for a repeat scan. Anecdotally, there is evidence to suggest that it is usually possible to see embryonic heart pulsation much earlier using modern ultrasound equipment. The aim of this study was to identify the smallest length of embryo when it is possible to always visualise heart pulsations during an ultrasound examination.nnMethod: This was a prospective observational study of women attending the early pregnancy unit of a large teaching hospital. Women were invited to participate when a clinically indicated ultrasound examination revealed an intrauterine pregnancy with an embryo measuring 6 mm or less. All women were symptomatic, i.e. they presented with pain and/or bleeding in early pregnancy. The presence or absence of discernible embryonic cardiac activity was recorded at the initial ultrasound examination, and any follow-up ultrasound examination, along with the crown rump length (CRL) of the embryo.nnResults: The study sample consisted of 95 embryos with CRL range 1˙2-6 mm. Visible heart pulsations were seen in 80 (84%) embryos at the initial examination. In 15 embryos, no discernible heart pulsation was noted; in all 15 cases, these pregnancies went on to miscarry: this was confirmed at a follow-up examination 7 days later.nnConclusion: In early pregnancy ultrasound, cardiac activity should be visualized in all live embryos as soon as the embryo can be identified reliably. The absence of heart pulsations in very small embryos is indicative of pregnancy demise, regardless of the actual size of the embryo.