Pearls and pitfalls of early obstetric ultrasound in the acute setting.

First trimester ultrasound is commonly performed to establish dates or evaluate early pregnancy complications. With improvement in ultrasound technology, visualization of fetal structures has improved. While the emergent evaluation does not typically focus on detailed fetal anatomic evaluation (since this is typically performed at 18-20 weeks), various fetal structural abnormalities can now be visualized, especially during the late first trimester and early second trimester. We present a pictorial review of potential pitfalls encountered in early obstetric ultrasound with an emphasis on fetal structural abnormalities as well as normal fetal anatomy that can be confused with developmental abnormalities.