First International Standards to Assess Fetal Growth and the Size of Newborns at Birth

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By: Katie Millar, Technical Writer, Women and Health Initiative, Harvard T.H. Chan School of Public Health

For the first time, the world has international standards for both fetal growth and newborn size. These standards have been developed by a global team led by scientists from Oxford

The international standards—one for the growing fetus and the other for newborns—are published today in two papers in The Lancet. They were developed as part of the landmark INTERGROWTH-21st Project, funded by the Bill & Melinda Gates Foundation, which took over 300 clinicians and researchers from 27 institutions across the world six years to complete. To produce the standards, almost 60,000 pregnant women were recruited in eight well-defined urban areas in Brazil, China, India, Italy, Kenya, Oman, the UK and USA. Of these women, over 4,600 healthy, well-nourished women with problem-free pregnancies were studied.

In a previous paper, these researchers declared that growth was not determined by race or ethnicity, but by the health of the mother. Growth can be standard around the world, and now we have a way to measure it.

Identifying Malnourished Newborns

These standards provide growth curves for fetal growth (measured by ultrasound) and for a newborn’s size at birth—including, weight, length and head circumference—according to gestational age. This is a breakthrough. Currently, over 100 differing growth charts are used around the world to assess fetal growth and newborn size. However, these only describe how newborns grow in a particular population, or region, and pose problems for both identifying and treating malnourished newborns. Now, with these new standards, clinicians around the world will be able to detect underweight and overweight newborns early in life.

Why International Standards are Important

Why is accurately measuring growth so important? As of 2010, 27% of births around the world, or 32.4 million babies a year in low- and middle-income countries, are born already undernourished. Poor growth evident by small for gestational age babies has a significant implication on an infant’s start to life—putting them at increased risk of illness and death compared to babies well-nourished at birth. Small birth size also increases a person’s risk of diabetes, high blood pressure, and cardiovascular disease in adulthood. In addition, caring for undernourished newborns puts incredible strain and economic burdens on health systems and societies.

But with these new standards, at least 13 million additional newborns—now considered ‘normal’ based on local charts—will be identified as being undernourished using their international standards globally each year.

“Being able to identify millions of additional undernourished babies at birth provides an opportunity for them to receive nutritional support and targeted treatment, without which close to 5% are likely to die in their first year or develop severe, long-term health problems,” says lead author Professor José Villar of Oxford University. “The huge improvement in health care we can achieve is unprecedented.”

Being born overweight is also a worsening problem, particularly in developed and emerging countries, as a result of rising maternal obesity rates due to overnutrition. Overweight babies are at increased risk of diabetes and high blood pressure later in life.

Reducing Mortality and Morbidities Worldwide

“These new standards for fetal growth and newborn size… are the best ways to compare populations across the globe. We hope their widespread use will contribute to improved birth outcomes and reduced perinatal mortality and morbidity worldwide. When combined with the existing WHO Child Growth Standards, it will be possible globally to make judgements on growth and size from early pregnancy to 5 years of age,’ said Professor Zulfiqar Bhutta, from The Aga Khan University in Karachi, Pakistan, and the Hospital for Sick Children in Toronto, Chair of the INTERGROWTH-21st Project Steering Committee.

Following the same approach as the WHO’s Multicentre Growth Reference, the new fetal and newborn standards will provide health practitioners worldwide with clinical tools to monitor growth from early pregnancy to school.

Next Steps

Now that we have these standards scale up is key. Professor Stephen Kennedy of Oxford University, one of the senior authors of the study, said, “We have produced the first international standards describing how babies in the womb should grow when they are provided with good health care and nutrition, and are living in a healthy environment. We now need to work with politicians and clinicians at regional, national and international levels to introduce the new tools into practice around the world.”

In order to access the complete package of recent publications and tools, follow the links below:

  1. International standards for fetal growth based on serial ultrasound measurements: the Fetal Growth Longitudinal
  2. International standards for newborn weight, length, and head circumference by gestational age and sex: the Newborn
  3. The likeness of fetal growth and newborn size across non-isolated populations in the INTERGROWTH-21st Project: the Fetal Growth Longitudinal Study and Newborn Cross-Sectional Study
  4. International standards for early fetal size and pregnancy dating based on ultrasound measurement of crown-rump length in the first trimester