Fetal heart tones can be heard with Doppler ultrasound at 10 to 12 weeks and with a normal stethoscope at 16 to 20 weeks. At 12 weeks of gestation, the uterus enters the abdomen and is palpable at the symphysis pubis; at roughly 20 weeks, it reaches the umbilicus. Uterine size is evaluated by measuring the distance from the symphysis pubis to the top of the fundus in centimeters. At roughly 20 to 35 weeks, the measurement in centimeters should equal the number of weeks of gestation. A discrepancy greater than 2 to 3 cm is called a size/date discrepancy. Ultrasound should be done for further evaluation (e.g., intrauterine growth retardation, multiple gestations). More test answers on https://studyhippo.com/usmle-step-2-secrets-ob/