A short segment on US in suspected pregnancy has been added to the Pregnancy page. Of particular note is the suggestion that using a high frequency linear probe may detect significantly more IUPs than a curvilinear transabdominal probe.
Tabbut, M, Harper, D, Gramer, D, et al. High-frequency linear transducer improves detection of an intrauterine pregnancy in first-trimester ultrasonography. The American Journal of Emergency Medicine http://dx.doi.org/10.1016/j.ajem.2015.11.001.