Ultrasound scans, fetal heart monitors and other devices can't get precise readings of the fetus if the mother carries a lot of additional weight.
如果母亲过度肥胖，超声波检查，胎儿心脏监测器和其他设备都不能得到胎儿的准确读数。
2
Fetal oxygen machines are designed to be used with traditional electronic monitors, which track heart rate to determine whether the fetus is experiencing stress or lacking oxygen.