How to locate where the fetal heart signal is,
The simplest way to learn how to find the fetal heart signal is to bring along your fetal doppler scanner to your next pre-natal check-up and ask the obstetrician to teach you. However, understandably, they are very busy. The more practical apporach is to observe how they find the position. And try to practice more when you are back home.
Since the fetus can move quite freely inside the womb, the location of its heart will change every second. Having said that, there are tricks on how we can identify its location,
A. Use the conduction media (be it hand cream or baby oil) liberally. Please be reminded one should avoid shaking the conduction media before use as the subsequent small but copious air bubbles will reflect rather than helping the ultrasound transmission
B. The probe should be relocated closely (1 cm) in each occasion. However, you should take chance on pointing the probe to different directions (area) when the probe is station in the same site on your tummy. Do not hurry! The more you reposition the probe, the less likely you will find the signal
C. Before the 24th week of gestation onward, the fetal heart is more likely to be central (between the belly button and the pubic bone). The more earlier the pregnancy, the more central the location will be.
D. The more advance the pregnancy, the position will be higher (closer to the chest). However, in the 36th week of pregnancy onward, the fetal heart will be between the belly button and the xiphoid process of the sternum. Also, it will be more likely to be in the sides rather than staying central.
E. Fetal heart signal is more clearly heard at the back. Since preceivable fetal movement is mainly due to his limbs, the side that you do not feel the fetal motion will be more likely you will find the fetal heart signal.
F. In the late stage of pregnancy, when the fetus has assumed an inverted position, the fetal heart will be below the belly button. Conversely, if he is still in a sitting postion, you should expect the signal be much higher up.
How to differentiate different types of sound?
There are lots of different sounds you will hear with the Sonotech Express fetal doppler. For example, the kicking sound of your baby, his hiccup, and the movement of your bowel. Each of them has a different pitch and character, with time and practice, you will be more confident in differentiate them. And it will be much more fun on using the fetal doppler.
In general, we describe the sound as following：
Baby kicking：A solid thrust
Baby hiccup：Two rapid and soft percussion
Your bowel：Quick hizzing
Fetal heart：A rapid gallop
Your heart: soft gallop
Baby kicking on a background of mother heart signal
Interference of the ultrasound or the probe is not stationary: alike incorrect tuning of the radio
Baby heart rate is much higher than that of the mother. The FHR ranges from 120 to 160bpm, while the heart rate of the mother is only at the range of 60 to 100bpm. If you are not sure, by feeling the pulse at your wrist, the difference will be lot more obvious.
What is the best timing listening to the fetal heart?
Using a fetal doppler scanner with 2MHz probe can allow picking up the fetal heart signal as early as 8th week of pregnancy. At this moment of time, the fetus is very small, at the size of few centimeter. The heart sound of it will, understandably, subtle. Furthermore, it might well be obscured by your heart sound and your bowel sound. As such, you have to be very careful and patient before you can master the technique of finding where the signal is.
When you just have your breakfast or any food, your bowel will be much more active (hence it will well cover the signal of the fetus). In such regards, the best timing of listening to the fetal heart is the time before you have any food (but not too hungry, of course), or 3 to 4 hours after you have your meal. Relax! That will slow down your heart rate and make life easier.
By the time the baby grows bigger (and hopefully you will have more experience with the fetal doppler machine), you will be able to locate the fetal heart signal quicker. At the same time, you will also be able to differentiate different kind of sounds as mentioned earlier in this page.
Have fun!