What is considered the first sonographic sign of early pregnancy?

The first sonographic sign of early pregnancy is the visualization of the gestational sac. This structure typically becomes visible around 4 to 5 weeks of gestation and is crucial for confirming a pregnancy via ultrasound. The gestational sac appears as a fluid-filled structure within the uterus and serves as the initial indicator that the pregnancy is developing appropriately.

Thickened endometrium may indicate early pregnancy as well, but it is not a definitive sonographic marker. Instead, it signifies the uterine preparation for implantation and can be seen in various conditions, not just pregnancy. The detection of fetal heartbeat occurs later, typically around 6 weeks, after the gestational sac is already visible. Embryo development also follows the identification of the gestational sac, as it is dependent on it. Therefore, visualization of the gestational sac stands out as the earliest identifiable sign of pregnancy using ultrasound.