Prenatal ultrasonography is a common procedure in many countries [1-4]. It is an accurate technique for determining gestational age, number of fetuses, fetal cardiac activity, and placental location. In addition, many congenital structural anomalies and significant abnormalities in fetal growth can be identified. However, whether all obstetrical patients should undergo ultrasound screening and whether such screening improves pregnancy outcome is controversial.
Many countries have developed local guidelines for the practice of prenatal ultrasonography and most offer at least one mid-trimester ultrasound examination as part of standard prenatal care, although worldwide obstetric practice varies . In the United States, the American College of Obstetricians and Gynecologists (ACOG) supports the use of ultrasound when there is a specific medical indication and advises against nonmedical use of prenatal ultrasonography (eg, to accommodate parental curiosity about fetal sex or parental desire to view and/or obtain an image of the fetus) [6,7]. ACOG also stated that the benefits and limitations of ultrasonography should be discussed with all patients, and performance of the procedure is reasonable in patients who request it. In addition, a 2006 workshop organized by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) reached a consensus that “all fetuses should have a screening ultrasonogram for the detection of fetal anomalies and pregnancy complications” .
An evidence-based discussion of the application of ultrasound to an unselected obstetric population as a screening tool will be presented here. The use of prenatal ultrasonography for specific obstetrical indications is reviewed separately. (See "Ultrasound examination in obstetrics and gynecology".)
CRITERIA FOR A GOOD SCREENING TEST
In general, a good screening test should be safe, have high sensitivity and specificity, ideally take only a few minutes to perform, require minimum preparation by the patient, and be inexpensive. It should identify individuals with an important disease or condition and be cost-effective, allowing for control of health care costs by identifying disease early and treating before the consequences of the disease are overwhelming. (See "Evidence-based approach to prevention", section on 'Methodologic issues in evaluating screening programs'.)
RATIONALE FOR ROUTINE SCREENING PRENATAL ULTRASOUND
It is hypothesized that routine use of ultrasound in all pregnancies will prove beneficial since adverse outcomes may occur in pregnancies without risk factors and clinical conditions that place the fetus at high risk may not be detected by clinical examination. The primary objective is to obtain information that will enable delivery of optimal antenatal care and thus the best possible outcomes for mother and fetus . However, the benefit of such prenatal sonographic screening on neonatal outcomes remains unproven.