Yi Ying Ong, Nicholas Beng Hui Ng and Yung Seng Lee
Imagine two babies born at full term. Baby A had a normal growth rate in the womb but is born naturally small, while Baby B is born small after their growth in the womb slowed down. Baby B’s “fetal growth deceleration” may have been caused by placental issues or other conditions limiting the baby’s nutrient and oxygen supply, potentially affecting their brain development. Research studies have often lumped Baby A and Baby B together under the categories of “low birthweight” or “small for gestational age”, but these conditions are different from slowed fetal growth. As such, it remains unclear how fetal growth deceleration affects children’s cognitive abilities.
Now, let’s look at what happens after birth — some believe that if Baby B’s growth catches up, it might compensate for the earlier growth problems and support better brain development. But is this true?
In our study recently published in IJE, we used data on babies in the Growing Up in Singapore Towards Healthy Outcomes (GUSTO) cohort to try to answer this question. We looked at how fetal and postnatal growth are associated with intelligence. As the link between premature birth and poorer brain development is already well-established, we instead focused on children who were born at term to see if any of them were also at risk.
We tracked fetal growth using ultrasounds at regular intervals and defined fetal growth deceleration based on changes in the baby’s abdominal circumference from the second to the third trimester. Abdominal circumference reflects nutritionally sensitive areas, like the liver and abdominal fat, which are affected by poor conditions in the uterus. After birth, we assessed the children’s intelligence using standardized tests when they were preschool age (4–4.5 years) and school age (7 years). Although not a perfect measure of intelligence, these tests allowed us to compare results between children and at different ages.
Nearly a quarter of term-born infants in our study experienced fetal growth deceleration, and this was linked to slightly lower intelligence quotient (IQ) scores (by about 4 points) at preschool age. However, there was no such association by the time the children were school age. This might be due to a natural catch-up in growth and development over time. Indeed, children in our cohort with fetal growth deceleration did show a gradual catch-up in weight, height and body mass index by age 7, even overtaking children without growth deceleration beyond this age. Further research would need to use detailed measurements like MRI to find out if this physical catch-up is matched by brain development. Another study similarly found that infants born small for gestational age at term who had a gradual catch-up in weight by age 7 didn’t have lower IQ scores.
Importantly, children with fetal growth deceleration who gained excessive weight between birth and the age of 7 years did show an association with lower IQ scores at school age. Other studies have found that greater gains in fat mass from infancy to preschool age were associated with lower IQ scores, and that there may be complex associations between adiposity and cognitive function involving changes in brain structure. This has important clinical implications — although paediatricians have long encouraged catch-up growth for infants who had poor fetal growth, it’s crucial to monitor the extent of this growth. We had already found that excessive catch-up growth after poor fetal growth is associated with higher blood pressure and insulin resistance in children, indicating a risk of cardiometabolic disease, so we now need to be aware of a possible link to lower intelligence as well.
Our study is unique in that we looked at changes in fetal abdominal circumference, which reflects the early or “pre-clinical” phase of fetal growth restriction. This novel approach might detect fetuses who are at risk but wouldn’t be detected using other measures, like head size measurements. Other studies have also reported slowing growth in fetal abdominal circumference as an indicator of fetal development, being associated with an increased risk of neonatal morbidity, reduced feto–placental blood flow, and poorer language and vision at 2 years of age.
Think of fetal growth as the foundation of a house. Regular prenatal ultrasounds act like inspections to identify any problems with the foundation. A child with a history of fetal growth deceleration is like a house with a shaky foundation. Just as a builder would carefully monitor and reinforce the structure, we need to monitor these children’s development. If a house is built too quickly and without proper support, it becomes unstable. Similarly, excessive weight gain in these children could lead to health problems, including potentially lower intelligence scores and higher cardiometabolic risk. With early detection, regular monitoring and careful management, we hope to ensure these children have a strong and stable foundation for their future, just like a well-built house.
Read more:
Ong YY, Ng NBH, Michael N, et al. Associations of fetal and postnatal growth trajectories with child cognition: the GUSTO cohort study. Int J Epidemiol 2025; 13 February. doi: 10.1093/ije/dyaf012
Dr Yi Ying Ong is a research assistant professor in the Department of Paediatrics at the Yong Loo Lin School of Medicine, National University of Singapore. She has worked closely with the Growing Up in Singapore Towards Healthy Outcomes (GUSTO) and Project Viva cohorts, focusing on early life growth, cardiometabolic health and neurodevelopment.
Dr Nicholas Beng Hui Ng is a consultant paediatrician at the National University Hospital, Singapore. His primary clinical and research interests are in paediatric growth, obesity and related metabolic complications.
Professor Yung Seng Lee is a professor of paediatrics at the Yong Loo Lin School of Medicine, National University of Singapore, and a senior consultant paediatrician practising paediatric endocrinology at the National University Hospital, Singapore. His clinical and research interests are focused on growth, obesity and diabetes.
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