yolk sac, fetal heart, in the first trimester

To establish exact data about the ultrasound image of early pregnancy and the detection rate of relevant structures, the vaginosonographic examinations of 259 normal intrauterine singleton pregnancies with reliable dates between 4 and 13 complete weeks menstrual age were analysed. The chorionic cavity as the first specific structure of pregnancy, was imaged in all cases. The chorion frondosum could be differentiated from the chorion laeve at 6/7 weeks. The yolk sac was reliably seen at 5 weeks. The embryo and its heart activity proving viability of pregnancy, were regularly found at 6 weeks...