Help please: late heart rate deceleration on NST

[herenow2]

Yesterday I went in for an NST.  The hospital where I plan to deliver likes women over age 35 to get them from week 36, but after discussing with my OB, I waited until 38.  Everything has been perfectly healthy this pregnancy and I was shocked when they came in after my first 20 minute strip and told me that I needed to get to L & D for extended monitoring.  Apparently, there was a late decel after a minor contraction (seemed to me to be a braxton hicks at the time which I get several times a day) going from a baseline of 140s to 117.  It did not happen for the next hour, so they sent me home  to come bakc for NSTs twice a week, but I don't think I had any braxton hicks so I am worried that the same conditions that caused the late decel weren't repeated.  

At first I was mad at what I was feeling were highly interventionist decisions, but now that I have read about late decels, I am scared and wondering if my regular braxton hicks are going to hurt the baby.  Does any one know if there are ANY other explanations for late decels other than placental malfunction?   This is my third baby and I have always done things really naturally in a hospital and things always went perfectly so this is all scary to me and I guess I should trust the doctors but would love to hear if any one else has experience with this or any insight.

Thanks.

[JenRN]

In my experience (LDRP nurse), late decelerations happen after every contraction, but there are other "warning" signs going on - low variability, no accelerations, etc. This isn't always the case, of course, but if they monitored you for awhile and let you go home, I'm betting there were no other warning signs. It could have just been a fluke thing. I would get the weekly NSTs just to make sure, but trust me - they wouldn't have let you go home if things looked bad, especially if your doctor is "interventionist."

One other thought is that the "late" decel could have been a variable deceleration with late timing (variable determined by the shape, looks like a "V", suddenly drops down then quickly comes back up. Going from 140s to 117 sounds like a variable, normally late decelerations are more subtle in shape. By late timing, I just mean it happened after the peak of a contraction - early would be lined up perfectly with the contraction, variable being whenever). Variables are caused by cord compression, so maybe baby just wiggled onto its cord for a minute then moved away? They can be cause by certain positions, and while normally benign, most of the time will go away if you change positions.

There are doctors that I work with that can look at the same fetal heart rate tracing and one will call it a late decel and the other will call it a variable, so there is room for human error/judgment there.

[herenow2]

Thank you Jen!  I keep telling myself they wouldn't send me home at 38 weeks if they were worried, they'd just induce or c-section.  But then I google late decelerations and get paranoid again.  Your input makes me feel better.