市塚 清健, 長谷川 潤一, 松岡 隆, 仲村 将光, 関沢 明彦

Kiyotake ICHIZUKA, Junichi HASEGAWA, Ryu MATSUOKA, Masamitsu NAKAMURA, Akihiko SEKIZAWA

昭和大学医学部産婦人科学講座

Department of Obstetrics and Gynecology, Showa University School of Medicine

キーワード : first trimester, fetal biometry, chorionicity, risk assessment for chromosomal abnormality, safety of ultrasound

妊娠初期における超音波検査の役割は，妊娠週数・出産予定日の確認，流産，異所性妊娠，胞状奇胎など異常妊娠の診断，比較的大きな胎児形態異常の有無，多胎妊娠の場合の膜性診断，子宮筋腫，卵巣腫瘍など婦人科疾患合併の有無などの検索である．最近では，それらに加え後頸部無エコー領域（nuchal translucency: NT）をはじめとした胎児染色体異常のリスク評価も加わってきた．NT以外の検査項目は，特に倫理的な問題は含んでおらず，基本的には診断した医師は患者に検査結果を伝える必要があるが，NTに関してはいわゆる出生前診断の一部と捉えられるため，検査結果のインパクトが大きい．さらに，その計測には一定の技術が求められる．したがって，検査を行う際には習熟したものが検者である必要があり，さらに検査結果はもとより，検査前に妊婦に本検査を受けてわかること，わからないことなど検査の本質をカウンセリングし，自己決定による希望者のみに行うことが望ましい．本稿では妊娠初期に行う超音波検査の進め方，方法さらに妊娠初期の超音波検査の安全性についても概説する．

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.