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SONOGRAPHY IN OBSTETRICSe. . . . . . . . . . . . . . . . . . .. 182
TECHNOLOGY AND SAFETYe. . . . . . . . . . . . . . . . . . . . . . 182
GESTATIONAL AGE ASSESSMENT . . . . . . . . . . . . . . . .. 183
FIRST-TRIMESTER SONOGRAPHY ....e.....e...e...... 185
SECOND-AND THIRD-TRIMESTER SONOGRAPHY .... 186
CERVICAL LENGTH ASSESSMENT. . . . . . . . . . . . . . . .. 189
NORMAL AND ABNORMAL FETAL ANATOMY. ....... 191
DOPPLER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
MAGNETIC RESONANCE IMAGING ....e...e.......... 215
After discovey of the Roentgen ray and the demonstration of the various uses to which it might be put, it was thought possible that it might also aord a valuable method ofinvestigating the shape and size of the pelvis.
-]. Whitridge Williams (1903)
X-ray techniques were just on the horizon when the first edition of this textbook was published. he first application focused on the maternal pelvis without attention to the fetus. hus, congenital abnormalities were routinely not discovered until birth. Subsequent radiographic eforts to evaluate the fetus were later replaced by ultrasonography and more recently by magnetic resonance (MR) imaging, techniques which have become increasingly sophisticated. he subspecialty of fetal medicine has developed only because of these advances, and today's practitioner can hardly imagine obstetrical care without them.
Prenatal sonography can be used to accurately assess gestational age, fetal number, viability, and placental location, and it can aid diagnosis of many fetal abnormalities. With improvements in resolution and image display, anomalies are increasingly detected in the irst trimester, and Doppler is used to manage pregnancies complicated by growth impairment or anemia. he American College of Obstetricians and Gynecologists (2016) recommends that prenatal sonography be performed in all pregnancies and considers it an important part of obstetrical care in the United States.