Understanding Embryonic Heart Rate: What's Normal?

Question
Hi,

I'm 37 years old and am pregnant with my fifth child.  I have 3 living children and lost our last child at 22weeks due to chromosome abnormality (T21)

I had my second sonogram today at 6w6d and ERH was recorded at 117bpm.  The sonographer told me they considered that to be a normal rate for gestational age but my last pregnancy the EHR was 152bpm at 7w5d.  I'm just worried that the rate recorded today is truly on the low end and after having such a heartbreaking loss last I'm paranoid.

Is 117bpm truly good for this gestational age?  Embryos crown rump length measure 7.0 weeks..

Thanks,
Abby

Answer
Dear Abby,

Normal fetal heart rate at 6 weeks is 90-113 bpm and at 9 weeks is 144-170 bpm. In a recent study, singleton pregnancies with an embryonic heart rate measured on a 6.0-7.0-week US scan were identified. "The heart rate was classified as slow if it was fewer than 90 beats per minute prior to 6.3 weeks or fewer than 110 beats/min at 6.3-7.0 weeks, normal if it was 100 or more beats/min at less than 6.3 weeks or 120 or more beats/min at 6.3-7.0 weeks, or borderline if it was 90-99 beats/min prior to 6.3 weeks or 110-119 beats/min at 6.3-7.0 weeks."

Your results of 117 bpm are ok. It is nothing that I would be alarmed about at this point. In fact, the 152 at 7 weeks for the last pregnancy would have been slightly higher than we'd normally see for that gestational age. EHR's increase steadily every day before tapering off at about the 9th week. In fact, today your average EHR will probably be up to about 124 bpm!

I know it's hard after a loss, but try not to worry. Enjoy each moment that you can!  :-)

I hope this has helped you and answered your question. I wish you well.

Brenda