Although a probe is typically applied externally to the abdomen, in some cases an obstetric ultrasound may involve a transvaginal probe inserted several inches into the vagina to help an obstetric sonographer check for a fetal heart beat early in pregnancy, determine a more accurate due date or asses the mother’s uterus and ovaries among other uses. Although most consider ultrasound to be a safe procedure during pregnancy, medical consensus recommends that its use be restricted to medically necessary situations only.
Limitations of Obstetric Ultrasound
Despite its indispensable role in the field obstetrics, obstetric sonography is limited by the fact that it does not reveal all possible fetal abnormalities. Further tests such as amniocentesis or chorionic villus sampling may be necessary. In amniocentesis, a small sample of the fluid surrounding the fetus is extracted for testing, and, in chorionic villus sampling, the placental tissue is tested for abnormalities. In some cases, a pregnant woman may be referred to a high-risk pregnancy obstetrician who may order additional ultrasounds but with the understanding that they may be limited in what problems they can show.