New research has shown that fetal growth restriction may affect babies' heart rate, pain response, brain structure, growth and early development long after birth.
For the first time, a study has tracked the growth of babies diagnosed with fetal growth restriction through from 14 weeks gestation to six years of age.
The researchers, from King's College London and University College London, have 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 dataset of participants between 14 weeks of gestation and six years of age to assess ongoing impacts of fetal growth restriction on energy, growth and motor and cognitive development.
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 around 3 beats per minute faster than other babies that are growing well. That is around 4,600 extra heartbeats a day and equivalent to a rate of a baby six 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 fetal growth restriction babies 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 the 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 7cm³ 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 one to two years, even after taking fetal growth restriction diagnosis into account.
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.
Dr Kimberley Whitehead, Senior Lecturer at King's College London and Corresponding Author
Study co-author Professor Anna David, UCL Institute for Women's Health and a fetal medicine expert who specialises 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 emphasises the urgent need to invest in therapies that can address this critical gap in pregnancy care."
