The fetal heart rate is usually 110-160 beats per minute, and between this frequency is considered normal. During early pregnancy, the fetal heart is usually detected only with ultrasound. In early pregnancy, the heart rate may increase to 170 beats per minute. After 12 weeks of pregnancy, when the uterus enlarges and protrudes into the pelvic cavity, the fetal heart can be heard in the abdomen with a fetal heart monitor. Usually, after 14 weeks of pregnancy, the fetal heartbeat will be more stable at 110-160 beats/min. During every maternity checkup, the doctor will routinely listen to the fetal heart, mainly to see if the fetal heart is normal and within the normal range, and if the fetal heart is abnormal, to check if there are any factors that cause the fetal heart to drop or increase in speed. The fetal heart monitoring can reflect the situation of the baby in the uterus, so it is very important to do fetal heart monitoring in the second trimester.