An ultrasound test at the end of pregnancy detects at-risk babies and prevents severe complications

A multicenter study, published in The Lancet and involving the Institut de Recerca Sant Joan de Déu, has shown that adding a Doppler study of fetal circulation in the last ultrasound can reduce by half the complications requiring admission to the neonatal intensive care unit (ICU) for full-term babies.

Determining the blood flow in the fetal brain and placenta using Doppler in routine third-trimester ultrasound allows for the detection of babies at risk of postpartum complications that may require admission to ICU. Inducing delivery at term in these high-risk cases could potentially reduce the neonatal ICU admission rate by up to half. This is demonstrated by an international multicenter study, named RATIO37, published in The Lancet.

The study led by Eduard Gratacos, research coordinator of the Foetal Medicine and Surgery at the IRSJD, and Francesc Figueras, Head of the Fetal Medicine Service at the Hospital Clínic de Barcelona (IDIBAPS), and supported by "la Caixa" Foundation, CEREBRA Foundation

Less than 1% of babies in low-risk pregnancies experience complications in the last 2-3 weeks of pregnancy or at birth that require admission to the ICU. Severe complications in babies from normal pregnancies are very rare, but when they occur, they are extremely traumatic for families.

A very common cause within this 1% is due to placenta malfunctions towards the end of pregnancy. This situation is known as placental insufficiency and can lead to oxygen deficiency in the baby when uterine contractions occur in late pregnancy and during labor. Detecting cases at risk of placental insufficiency is crucial because it allows for assessing the possibility of ending the pregnancy at full term (37 weeks) and significantly reducing or even avoiding serious complications.

A Doppler ultrasound test measuring blood flow in the umbilical cord and brain, called the cerebroplacental ratio (CPR), can detect placental insufficiency. Thus far, this test was only conducted in pregnancies with complications and in very specific cases.

The research considered the possibility of extending the study of placental function with CPR to the third-trimester ultrasound of all fetuses, regardless of the estimated fetal weight.

In the RATIO37 study, more than 11,500 women with low-risk pregnancies have participated for six years. At the 36-week ultrasound, CPR was measured in all women, but the participants were randomly divided into two groups. In one group, the test was used to change the management of the pregnancy and if the results were abnormal, early induction of labor was proposed when reaching full term. In the other group, the test results were not communicated, and the pregnancy was managed according to existing protocols. The study compared the number of infant deaths and the occurrence of severe neonatal complications (including, among others, neurological, intestinal, cardiac, renal, or respiratory problems requiring ICU stay for 10 or more days) in each group.

The results demonstrated that there were severe neonatal complications in 0.38% of pregnancies when CPR was measured and 0.73% when it was not measured. It took a study of this magnitude to show a seemingly small difference, but it represents a reduction of 3.5 cases of severe complications per 1000 pregnancies classified as "low risk." If these figures are extrapolated to the total number of births in Spain in 2022 (330,000), it could prevent 1,150 severe neonatal complications.

"The results are highly relevant; they provide compelling data that will be fundamental in a scientific debate spanning over 10 years and make progress in the development of better ways to refine the detection of high-risk pregnancies and prevent serious neonatal complications. Over the next few years, these results will generate discussions in societies and conferences. The application of these findings in each context will need to be evaluated. However, they will undoubtedly motivate changes in the recommendations of many professional pregnancy control guidelines worldwide," explains Dr. Gratacós, Director of BCNatal (comprising Hospital Sant Joan de Déu - IRSJD and Hospital Clínic - IDIBAPS.

This study demonstrates that it is possible to identify much more selectively, specifically 5% of pregnancies that truly benefit from a measure like labor induction, representing an advance towards personalized and minimally invasive maternal-fetal medicine.

Reference paper

Marta Rial-Crestelo, et al. Term planned delivery based on fetal growth assessment with or without the cerebroplacental ratio in low-risk pregnancies (RATIO37): an international, multicentre, openlabel, randomised controlled trial. The Lancet. January 11, 2024. DOI:

BCNatal is the author of the photo · From left to right, Francesc Figueres, Marta Rial-Crestelo and Eduard Gratacós.

These results enhance the current ability to identify high-risk cases and implement solutions that can prevent severe complications for the baby.