Routine ultrasound in the second trimester

Historically, first attempts on fetal screening were held on Northern Europe in 70's. Ultrasonographic evaluation of the pregnancy has advanced rapidly in the past decades. However, the routine use of ultrasound in the second trimester of pregnancy was controversial. In addition, indications, timing and quality of machine were the main debates. In 80's and early 9()'s, routine use of the ultrasound was not recommended especially in western countries because of lack of evidence on the improvement of perinatal outcome. While there are still great differences on the detection of fetal anomalies because of the skill of the operator and quality of the machine, routine use of ultrasonography is now well-accepted as a standard obstetrical care in many centers around the world.
Not only verification of gestational age and viability, but also investigation for entire fetal anatomy should be done. Other main purposes of the ultrasound screening are to allow liming and transporting to referral center for delivery, alternative options, for antenatal and/or postnatal therapy.
Principles of investigation consist cardiac activity, number of fetuses and presentation, amniotic fluid volume, placental localization and structure, measurements of BPD, HC, AC and FL. examination of the myometrium, adnexa and cervical canal and finally fetal anatomy. Examination of fetal anatomy is not an option, but should be a standard. Absence of a normal system or organ, presence of an extra structure, herniation from a defect, dilation behind an obstruction, abnormal biometry, lack of fetal movements are the alarming signs. In addition, soft markers of aneuploidy should be investigated in the second trimester of pregnancy.

Finally, screening programs which are predictive and highly specific may reassure some parents falsely or make them anxious leading to invasive procedures. Such programs may also be subject of malpractice. Cost effectiveness and educational problems for these screening programs are still subjects of debate.