Routine First-Trimester Ultrasounds Are Proving Key to Earlier Detection of Serious Fetal Anomalies

A new nationwide study from England is offering strong evidence that routine first-trimester ultrasounds can detect major fetal anomalies weeks earlier than the standard second-trimester scan. The research, led by specialists at the University of Oxford, reviewed more than 1 million pregnancies and compared how different hospitals approach early pregnancy ultrasound imaging. The findings show a clear pattern: when hospitals use detailed first-trimester scanning protocols, they identify significantly more fetal anomalies before 16 weeks of pregnancy.

Across England, the typical prenatal care pathway includes a basic 12-week scan to determine gestational age and a 20-week scan designed specifically to identify congenital anomalies. These anomalies affect roughly 2–3% of all pregnancies, and traditionally, the second-trimester scan has been considered the main tool for spotting them. But improvements in imaging technology now make it possible to examine fetal structure far earlier, raising the question of whether early detection should become a consistent, national standard.

The study, which analyzed pregnancies from April 2017 to March 2019, found substantial variation in how hospitals perform first-trimester ultrasounds. Some offer no structured anatomical assessment at all, while others follow extended, highly detailed protocols. Researchers grouped hospitals into four categories: those with no anatomical protocol, those offering basic assessment, those using advanced assessment, and those following extended protocols.

After linking hospital scanning policies with national congenital anomaly data, the researchers found that the level of detail in the first-trimester scan directly influenced how early anomalies were detected. Hospitals with extended protocols identified about 40% of major anomalies before 16 weeks. In contrast, hospitals that performed no structured first-trimester anomaly assessment detected only about 28% early.

Not all anomalies behaved the same. Certain conditions, such as acrania, where the fetal skull fails to form, were typically caught early regardless of hospital policy because they are visually obvious even on less detailed scans. But more subtle and complex anomalies—like heart defects and limb abnormalities—were much more likely to be detected early only in hospitals using detailed early-pregnancy scanning.

Because the study used hospital-level policies rather than individual scan records, it could not confirm that every patient actually received the specific protocol used by their hospital. However, the large dataset clearly shows that hospitals prepared to conduct thorough early assessments achieve better early-detection outcomes overall. The researchers emphasized that the lack of consistent national guidelines has resulted in highly uneven care across England. In their view, requiring detailed first-trimester screening nationwide would create a more equitable and effective system for prenatal anomaly detection.

Several experts involved in the study stressed that earlier diagnosis gives families more time to understand their situation and consider clinical options, including specialized monitoring, early interventions in select cases, or preparing for neonatal care needs. They also pointed out that ongoing improvements in ultrasound technology mean modern equipment can reveal fetal structures in far greater detail than in the past.

Why Early Detection Matters

Fetal anomalies can range from minor correctable conditions to severe or life-limiting disorders. Detecting them earlier in pregnancy offers multiple benefits. Families get more time to process information, meet with specialists, and make decisions that feel right for them. Clinicians can prepare tailored monitoring plans or arrange appropriate delivery settings. In rare cases, early detection may even open the door to prenatal treatment or fetal surgery for certain conditions.

Research has consistently shown that combining first- and second-trimester scans significantly improves overall detection rates compared to relying only on the 20-week scan. Earlier studies reviewing millions of pregnancies found that first-trimester scans alone detect around one-third of structural anomalies on average, but performance varies by anomaly type. When combined with the detailed 20-week scan, the sensitivity increases dramatically. The new nationwide study from England strengthens this evidence at a real-world, population level.

Another important element is consistency. Without national guidelines, hospitals differ widely in their approach. Some have invested in training and equipment for detailed early assessment; others offer only basic early scans due to resource limitations or outdated policy frameworks. The new findings suggest that establishing a consistent national standard could significantly improve early-detection rates across the board.

What Types of Anomalies Can Be Detected Early

The ability to identify specific anomalies in the first trimester depends on their nature and how they develop. Conditions like acrania, exomphalos, and gastroschisis can often be seen early because they dramatically alter fetal anatomy. Meanwhile, complex anomalies—especially congenital heart defects, which require careful imaging of tiny cardiac structures—tend to require more skilled operators and more advanced equipment.

The study’s findings reinforce this: hospitals with detailed protocols detected far more of these subtle conditions early. This underscores how important sonographer training, technology quality, and standardized protocols are for achieving consistent results.

How Imaging Technology Has Improved

Modern ultrasound machines provide higher-resolution images, better depth penetration, and enhanced Doppler capabilities compared to older models. These advancements allow clinicians to visualize fetal anatomy sooner and with increased clarity. Some centers are also integrating AI-assisted tools that help flag unusual patterns, although these technologies are still developing and not yet standard practice.

As imaging continues to improve, the line between what is possible at 12 weeks and what once required a 20-week scan is shifting. This raises the importance of updating guidelines so they reflect current capabilities rather than outdated assumptions.

Challenges and Limitations to Keep in Mind

Despite the strong evidence supporting early screening, there are limitations and practical considerations. First-trimester ultrasounds are more technically demanding because the fetus is very small. This means detection rates can vary depending on operator expertise and equipment quality. The study itself did not include individual scan data, which means researchers could not account for differences within hospitals or evaluate the exact performance of specific sonographers.

Additionally, not every anomaly can reliably be detected early. Some develop later or become easier to visualize as the fetus grows. False positives are uncommon but still possible, and they can create anxiety for families. That said, the overall accuracy of early scans is high, and experienced centers typically combine early findings with follow-up tests for confirmation.

Why This Study Could Change Policy

The key contribution of this research is its scale and real-world relevance. Studying more than a million pregnancies across an entire country provides insight that smaller clinical trials cannot match. The authors argue that the data make a clear case for implementing organized first-trimester anomaly screening across the NHS.

If policymakers adopt this recommendation, early pregnancy care in England could undergo a meaningful transformation. Instead of a patchwork of practices, expectant families would receive a more uniform, evidence-based standard of care. Early detection could become the norm rather than a fortunate outcome reserved for hospitals with more advanced protocols.

At its core, the research highlights a simple idea: using the technology and knowledge we already have, clinicians can identify many serious fetal conditions earlier than ever before. Doing so consistently may help improve both clinical outcomes and the overall experience for families.

Research Reference

Impact of first-trimester ultrasound on early detection of major fetal anomalies: Nationwide population-based study of over 1 million pregnancies
https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1004709