Babies with fetal growth restriction may face years of developmental effects, from heart rate to brain growth

Fetal growth restriction may affect babies’ heart rate, pain response, brain structure, growth and early development long after birth, according to a new study led by UCL and King’s College London researchers. For the first time, a study has tracked the growth of babies diagnosed with fetal growth restriction from 14 weeks’ gestation to 6 years of age. The authors of the new Scientific Reports paper found that differences experienced in utero, such as higher heart rate and lower weight, can persist after birth and cause compounding disadvantages into early childhood.

Fetal growth restriction happens when a baby does not grow as expected in the womb, often because the placenta is not able to provide enough oxygen and nutrients. Often this means an unborn baby with fetal growth restriction has an estimated size within the smallest 3%.

The new study curated a unique composite data set of participants from 14 weeks’ gestation to 6 years of age to assess ongoing impacts of fetal growth restriction on energy, growth, and motor and cognitive development.

Lead author Dr. Kimberley Whitehead, who began the work at UCL before moving to King’s College London, said, “These findings show that fetal growth restriction affects much more than size at birth. It can influence how babies use energy, how they respond to pain, how the brain develops and how children grow after birth.

“For health, care and early-year education practitioners, this highlights the importance of seeing fetal growth restriction as an ongoing developmental vulnerability. Careful monitoring and timely support may help children affected by fetal growth restriction reach their potential.”

Heart rate and pain response

Researchers found that babies affected by fetal growth restriction had a higher heart rate both before and after birth. On average, their hearts beat about 3 beats per minute faster than other babies who were growing well. That is around 4,600 extra heartbeats a day and is equivalent to the rate of a baby 6 weeks younger.

Heart rate increase during a routine heel-prick test can be used to measure a baby’s pain response. The study found that babies with fetal growth restriction showed only around half the usual heart rate increase during these tests. While the babies show a dampened pain response, this result does not mean the babies feel less pain, but suggests that they may not show stress in the same way as other babies.

Growth and motor development

MRI brain scans showed that babies affected by fetal growth restriction had significantly less white matter, around 7 cm³ less. White matter enables different areas of the brain to communicate with each other. The findings suggest this is due to the body adapting to reduced energy in the womb by limiting brain development to conserve resources.

The study showed children affected by fetal growth restriction tended to gain weight more slowly and often remained smaller than their peers. Poorer growth was also linked to less optimal motor and cognitive development at 1 to 2 years, even after taking fetal growth restriction diagnosis into account.

Study co-author Professor Anna David, UCL Institute for Women’s Health and a fetal medicine expert who specializes in fetal growth restriction, said, “This is important information to counsel parents who have a baby with fetal growth restriction, as their child may need extra support as they grow and develop. Currently there is no treatment that can improve the growth of a baby before birth. This study emphasizes the urgent need to invest in therapies that can address this critical gap in pregnancy care.”

Co-author Professor Lorenzo Fabrizi (UCL Neuroscience, Physiology & Pharmacology) said, “This work is a fantastic example of what can be achieved through open science! It reflects a substantial effort to harmonize data sets from different countries and shows how bringing these data together can reveal long-term developmental trajectories that extend well beyond the duration of any single study.”

Who’s behind this story?

Lisa Lock

BA art history, MA material culture. Former museum editor, paramedic, and transplant coordinator. Editing for Science X since 2021.

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Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

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