Mahoney C J, Eisele S
J Med Primatol. 1976;5(5):284-95. doi: 10.1159/000459973.
Ultrasonic stethoscopy proved to be a reliable and convenient technique for determing fetal viability in Macaca mulatta. Examinations, begun at day 150 of gestation in 33 monkeys and between days 32 and 58 in four other animals, were repeated at intervals of one to seven days. The earliest time of detecting blood flow in the fetal placenta was 42 days of gestation, fetal heart sounds geing discerned later. Three types of fetal cardiac rhythms were recognized: (1) a constant rate during most of pregnancy, (2) fluctuations associated with uterine contractions during labor, and (3) sudden transient bradycardia during violent rotations of the cephalically presented fetus.
事实证明，超声听诊是一种可靠且便捷的技术，可用于确定猕猴胎儿的活力。对33只猴子在妊娠第150天开始进行检查，另外4只动物在妊娠第32至58天开始检查，检查间隔为1至7天。检测到胎儿胎盘血流的最早时间是妊娠42天，胎儿心音稍后可被辨别。识别出三种类型的胎儿心律：（1）在妊娠大部分时间内心率恒定；（2）分娩时与子宫收缩相关的波动；（3）头先露胎儿剧烈旋转时突然出现的短暂心动过缓。
