fetal heartrate question

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nmpiche's picture
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fetal heartrate question

Hi All. When I went in for my u/s on Monday, baby was measuring 7w5d and heartrate was 162bpm. I was just looking up heart rates, and I found this article (link below). Basically, it says heartbeat increases 3bpm per day in the month after the 5th week. Since one week before the heartbeat was 124bpm by u/s, how could it have increased so much? First of all I am freaking myself out (because I am so worried about losing this pregnancy). Secondly, the article says sometimes they date the fetus by heartrate. I thought I was due Jan 16, but based on measurements, I am due Jan 26. What do you think? Am I driving myself crazy for nothing?

http://pregnancy.about.com/od/fetus/a/normal-fetal-heart-rate.htm

nmpiche's picture
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Now I found this formula: EMBRYONIC AGE in DAYS = EHR(0.3)+6
EHR is embryonic heart rate
This only works up to week 9 (after that HR drops a bit and that's normal).

That would put me at 7w6d. Well, I measured at 7w5d. Hmm, guess I should stop worrying. For you science/math geeks the R-squared value is 0.78 (not a bad correlation, hmm?).

This is from this reference:
http://www.obgyn.net/medical.asp?page=/english/pubs/features/dubose/ehr-age

turtnjay's picture
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Definitely step away from the equations! Lol

The heart rate can change because of activity or rest periods so when you fond it one time it may be super high and then later the same day much lower. if the baby was active or had just stopped an active period, it would easily account for any discrepancies.

I know how hard it is not to worry...I was a MESS yesterday and this morning waiting for my first scan but try to relax and know that you have a happy, healthy baby growing!

JuneorJulyBaby?'s picture
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Anything between 120-170 ( I think ) is normal so I wouldn't worry about it. If it is very early on then anything over 100 is good too. Like pp said, it really just depends if baby is in the "active" time or "sleepy" time and what you ate before the appointment. I would try not to over-analyze the fact that YOU SAW A HEARTBEAT!!!!

Science/math nerd alert: A correlation of 0.78 really isn't that good...it's only good in the social sciences that hope for some sort of relation. For truely quantitative results it should be in the mid-high 90's.

Jenn0113's picture
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"turtnjay" wrote:

Definitely step away from the equations! Lol

ROFL Please - these math equations are taking me back to HS algebra and I may just have a panic attack! LOL

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*lurker*
I wouldn't worry much about formulas and what heart rates SHOULD be
The first heart rate we saw with my son was 163 at not even 6 weeks! According to that formula, he should have had that rate at closer to 8 weeks