Early pregnancy ultrasound and hCG dynamics

The probe is in, the uterus is empty, and the registrar beside you says "her hCG is 2400, so it must be ectopic." That sentence has ended wanted pregnancies. This topic exists so that you can say, out loud and with the data behind you, why the number never locates the pregnancy — and what does.^[6][16]

Overview and definition

Two instruments, one question: where is this pregnancy, and is it alive? Ultrasound answers where. Serial hCG answers how the trophoblast is behaving. Neither answers the other's question, and almost every error in early pregnancy comes from asking one of them to.^[12][15]

Connolly measured both in the same population. Levels at which structures were predicted to be seen 99% of the time were 3510 mIU/mL for a gestational sac, 17 716 for a yolk sac and 47 685 for a fetal pole — far above the values currently used in practice. The threshold values, the lowest at which each was ever seen, were 390, 1094 and 1394 mIU/mL.^[6]

References20ShowHide

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