First-trimester anomaly scan: Balancing benefits and harms in a national screening program

There is increasing evidence that a significant proportion of fetal anomalies identified during the second-trimester anomaly scan can already be detected earlier in pregnancy. The first-trimester anomaly scan (FTAS) was introduced into the Dutch prenatal screening program in September 2021, aiming to detect major congenital anomalies earlier in pregnancy. The nationwide “Implementation of first Trimester Anomaly Scan” (IMITAS) study was conducted to evaluate its introduction. This thesis examined whether the FTAS is a valuable addition to the Dutch prenatal screening program and, if so, how it should be implemented in the future.
The findings show that the FTAS improves the early detection of severe fetal anomalies, including anomalies such as spina bifida and complex heart defects. Earlier detection provides parents with more time for additional testing and decision-making. For some parents, it also makes it possible to choose pregnancy termination at an earlier stage. Our results showed that earlier pregnancy termination is generally associated with a lower psychological impact than later pregnancy termination, although the emotional consequences remain substantial in both groups.
On the harms side, the first year of the FTAS showed a substantial proportion of cases where anomalies suspected at 13 weeks were not confirmed or resolved. This can result in additional tests, prolonged uncertainty, and increased anxiety for parents. Balancing the benefits of earlier detection with the risk of unnecessary worry remains an important challenge.
Overall, the findings suggest that the benefits-to-harms ratio of the FTAS is favourable, although this strongly depends on the perspective taken and how different outcomes are weighted. For pregnant women with a normal result, the FTAS can provide earlier reassurance, while potential disadvantages include the possible longer-term consequences of false-positive findings, as well as the associated costs and increased pressure on healthcare services. In addition, there is still room for improvement of the screening process, including the natural learning curve of healthcare professionals.
All results of the IMITAS study have been submitted to the Dutch Health Council, which is expected to publish its recommendation in September 2026 on whether the FTAS should be continued and how it should be implemented. The final decision will be made by the Dutch Ministry of Health, Welfare and Sport.