The fetal heart rate will change during the second trimester, just as it changes throughout the various stages of pregnancy. In fact, the fetal heart rate can change on a moment-by-moment basis, in response to various stimuli or various conditions that can be affecting your baby. While your baby’s heart rate does tend to spike briefly around the age of ten weeks of pregnancy, by the time that the second trimester rolls around, your baby’s heart rate will not change much until after your baby is born.
The fetal heart rate can, typically, be heard at around eight to ten weeks of pregnancy, depending on the mother’s body size and the method used to find the fetal heart rate, whether a transvaginal ultrasound or a Doppler or some other method. At around the tenth week of pregnancy, roughly three weeks before the second trimester begins, the fetal heart rate will peak at around 175 beats per minute. By week fifteen, which is during the very early part of the second trimester, the fetal heart rate will have dropped down to around 140 beats per minute.
It was once thought that the fetal heart rate could predict your baby’s gender. It was thought that, if a baby’s heart rate was under 140 beats per minute that it would be a boy, and that if it was over 140 beats per minute it would be a girl. The theory behind this idea was that, because women usually have a higher metabolic rate than men, that unborn girls would have a slightly higher pulse rate than unborn boys. However, most research does seem to disprove this idea, and demonstrate that there is not necessarily a connection between the fetal heart rate and the gender of your baby.
If you have concerns about your fetal heart rate, you should speak with your health care provider. Your health care provider can help to interpret what a high or a low fetal heart rate might mean, as well as help to figure out if it indicates some sort of a problem that will need to be addressed.