Now I want to talk more about the heart tones because the only thing we've mentioned so far
is when you can't first hear them, but there are some other things to think about. The first
thing is the rate. If you ever have an opportunity to hear fetal heart tones, they are very
fast. So the rate for a normal fetus is somewhere between 110 and 160 beats per minute.
Try to count it, it's really tricky. So for an adult, that would be tachycardia but very normal
for a fetus. So when should we hear that? Exactly, 10 weeks. Now the other thing we want to
think about is where to listen because there is a lot of abdominal space and only certain
places where we will be able to hear the heart rate. So at around 10 weeks, the fetus is really
just beginning to grow, the uterus is coming right above the level of the symphysis pubis
around 12 weeks or so, so we're going to be listening right over the symphysis pubis. That
one's not too hard. But as the uterus grows and the baby gets bigger, we have to really
know what the position of the fetus is. Because the best place to auscultate fetal heart tones
is on the upper back and in order to auscultate over the upper back, you have to know where
that is. Okay? We're going to use a measurement called Leopold's that we'll talk about in
just a second.