No scientific evidence has been identified to study the efficacy and the safety of ultrasound as a form of pregnancy control in primary health care. Even so, there is sufficient scientific evidence to conclude that routine or screening ultrasound versus selective ultrasound does not improve perinatal mortality, although it does improve determination of foetal age and detects multiple pregnancy earlier, as well as unsuspected foetal malformations.
There is sufficient scientific evidence to conclude that routine ultrasound is harmless. However, it should not be forgotten that a different aspect of the harmlessness of the technique is the safety of the obstetrical ultrasound attributable to false positive and negative. A false negative result may lead to a lack of medical care for a foetus that really needs it. On the other hand, a false positive result may give rise to unnecessary psychological anxiety in the parents, an exposure to the invasiveness of the prenatal confirmation diagnostic test and the greater economic cost involved in unnecessary testing.
The adoption of a new technology such as the ultrasound in primary health care may bring consequences that must be assessed in the decision-making processes associated to health planning - affecting quality of the health care process, supply and demand for tests of this kind and fair provision.
The revision of clinical practice guidelines and protocols on the clinical applicability of ultrasound screening have shown the existence of discrepancy depending on authors. Thus, while some recommend that three ultrasounds be conducted, others question this strategy on the grounds that there is no scientific evidence to justify such an approach. Therefore, the number of ultrasounds to be conducted in pregnancy, as well as the indication, might not be determined by clinical criteria.