Heart beat on early ultrasound

[BG-MN]

I am 45˝, pregnant without fertility treatments (1st pregnancy). Weeks 4 and 5 HCG levels doubled appropriately. Last week I had a vaginal ultrasound at the RE clinic where I'd been evaluated previously. The RE is very nice, but doesn’t sugarcoat the statistics for women my age, so he began the appointment preparing us that the US results might not be good. But then the US showed a gestational sac and heartbeat; he then said the pregnancy looked “viable” and he was “cautiously optimistic.” The US was done at 6w5d (sure about date of lmp). The g. sac measured only 5w5d, and the fetus size was 6w1d. The RE didn’t seem concerned about the difference in dates, but said he would like to see the heart beating “a little faster.” He wants to see me again for another US at 9w before referring me to a MFSH. My husband thinks the repeat US is due solely to the risks associated with my age, not the actual US results. But I’m worrying both about the heart rate and the fact that the fetus seems a bit “behind” in its development. Why do you think he wants another ultrasound? And is there any danger to the fetus in repeating an ultrasound so soon? I've read that the presence of an early heart beat is a very good sign the pregnancy will continue, but is that not as true for women my age? In case it’s relevant, I’ve had a bit of mild cramping during the pregnancy, but no bleeding; I’ve been on vaginal progesterone since 4w5d, as initially my level was low-normal. Thank you!  

[Forum-M.D.-SP]

First of all, it is great news that you are pregnant! Big first step. Now for the statistics:

1) When someone your age gets pregnant, there is, unfortunately, a > 60% chance of the pregnancy ending in a miscarriage and < 40% chance of having a liveborn baby.

2) The presence of a heart beat is a good thing! It definitely means the odds of having an ongoing pregnancy are > 50%

3) Hard to comment on the slow heart rate. At only 6 weeks 1 day, the baby's heart rate will be slower than it will be at 9 weeks. As a rule of thumb, when the heart rate at 6w1d is 100 or more, the chances of an ongoing pregnancy (in younger women) is probably > 90%. If < 100 (in younger women) the chances are still pretty good but drop to around 60%. At 6.5-7.0 weeks and beyond, the cutoff number becomes 120 beats per minute.

4) I too am not worried about a 6w1d ultrasound at 6w5d. Ultrasound accurracy is +/- 5-7 days at this stage, and you may have ovulated a day or two late.

I know this is going to be a long wait for you, but you have already passed two huge hurdles: just getting pregnant in the first place, and seeing a heart beat on ultrasound. You are on progesterone. The rest is out of our hands at this point. Good luck!

[aimntrev]

Do you know what the heartbeat was? I know when I went in at 6 weeks 5 days her heartbeat was only 126 and 2 weeks later it was up to 170.  The heartbeat gets faster as the fetus grows.  At 6 weeks, it's heart just started beating and that's why it's slower.  My doctor did an ultrasound at 6 weeks 5 days and then again at 8 weeks 5 days. I think she mostly did it, because I was very sure of my lmp but the baby was a little behind (which is normal some babies grow faster in the beginning then others) but I ovulated late, and she just wanted to make sure the baby was growing on pace and to help keep me calm,since  I had a previous miscarriage.

[BG-MN]

Thanks for your comments.  We weren't told the heart rate, but It's good to know it can be slow to start out, and that there are normal variations in growth....