Ultrasound examination at the first trimester

The purpose of performing an ultrasound examination in the early stage of pregnancy is to confirm the gestational weeks of pregnancy, expected delivery date, diagnoses for abnormal pregnancies such as miscarriages, ectopic pregnancy, hydatidiform moles, etc., the presence of relatively large fetal morphological abnormalities, chorionicity diagnoses in the case of multiple pregnancies, and searching for the presence of gynecologic diseases complicating the pregnancy such as uterine myoma, ovarian tumors, etc. In recent years, the evaluation risk for fetal chromosomal abnormalities including the anechoic area of the posterior region of the neck (nuchal translucency, hereinafter referred to as NT) has been added to the abovementioned items. Investigations other than NT do not have any particular ethical issues and the doctor making the diagnosis is required to provide patients with the investigation results; however, NT is regarded as a so-called prenatal diagnosis, meaning there is a great impact on the investigation results. Furthermore, a consistent technique is required for the measurement of NT. Accordingly, a tester carrying out the investigation must be skilled in this technique and, along with the evaluation results, it is desirable to counsel pregnant women in advance regarding the nature of the investigation with regard to the potential that some things may be found and others not found upon undergoing this investigation; therefore, it should be carried out only for those who are interested in self-determination. In this paper, an overview is provided regarding the procedures and method of performing an ultrasound examination in the early stage of pregnancy, along with the safety of ultrasound examinations in the early stage of pregnancy.