ABSTRACT
The use of ultrasound in obstetrics and gynaecology was first described by Ian Donald in 1958,1 and subsequently the first demonstration of an early intrauterine pregnancy by means of transvaginal ultrasound was reported in 1967.2 Since then with the advent of high resolution ultrasound it has been possible to study normal human pregnancy development in vivo from as early as the 3rd week postimplantation onwards. Studies have shown that the transvaginal route is
superior to the transabdominal route at gestations less than 10 weeks in particular for women who are overweight. It also offers the benefit that it does not require a full bladder, so can be performed immediately and is advantageous in those women who are nil by mouth or vomiting.3-5 Importantly, transvaginal scans have been shown to give clearer images at an earlier gestation as the transvaginal probe is much closer to the organs of interest.4 There is still, however, a use for transabdominal scans in early pregnancy, particularly in women with fibroid uteri and ovarian cysts. Improvements in early pregnancy imaging led to
the evolution of the early pregnancy assessment unit,6
providing reassurance for those with normal pregnancies and earlier diagnosis and management for abnormal pregnancies. In order to successfully diagnose abnormal pregnancy development it is fundamental to first understand what is normal. In this chapter, we describe the first 14 weeks of
development of a normal early pregnancy dealing exclusively with singleton gestation and then compare the ultrasound features of normal pregnancy with abnormal early pregnancy development.
