New International Standards for Fetal Growth‏, Newborn Size

Laurie Barclay, MD

September 10, 2014

The first international standards for fetal growth and newborn size reflect a universally healthy growth pattern from conception to birth, regardless of nationality or ethnic origin, according to 2 studies published in the September 6 issue of the Lancet. Adherence to these new standards could help prevent stunting and obesity by early recognition of deviation from the norm.

The 2 studies, both part of the International Fetal and Newborn Growth Consortium for the 21st Century (INTERGROWTH-21st) Project, are the Fetal Growth Longitudinal Study and the Newborn Cross-Sectional Study.

"Healthcare practitioners already have [World Health Organization] international growth standards for children from birth up to the age of 5 that are used in 140 countries worldwide," Newborn Cross-Sectional Study lead author José Villar, MD, professor of perinatal medicine at the Nuffield Department of Obstetrics and Gynaecology, University of Oxford, United Kingdom, said in a journal news release. "Now they will have international standards for the developing fetus and newborn too."

At present, clinicians around the world measure fetal growth and newborn size using more than 100 different locally produced growth charts. These charts are population- and/or region-specific, and they fail to reflect ideal growth in utero when mothers have adequate health, nutrition, and socioeconomic status.

"With these [new] international standards, we will know when the nutrition and healthcare needs of the developing baby are not being met," Dr. Villar said. "Across the world, this will help identify signs of under-nutrition, stunting, wasting, and overweight at an earlier stage to implement preventive actions to reduce long-term health problems, such as diabetes and hypertension."

The INTERGROWTH-21st Project consists of 3 studies that gathered growth, health, nutrition and, neurodevelopment data from less than 14 weeks and 0 days of gestation to 2 years of age in 8 diverse populations of babies born in selected urban areas in Brazil, China, India, Italy, Kenya, Oman, the United Kingdom, and the United States. Selection criteria included exposure to an ideal environment for healthy growth in utero, including good nutrition, education, low levels of environmental contaminants, and access to good healthcare, according to Aris T. Papageorghiou, MD, from the Nuffield Department of Obstetrics and Gynaecology and the Oxford Maternal and Perinatal Health Institute, Green Templeton College. Participants in the Fetal Growth Longitudinal Study (n = 4607) underwent fetal ultrasound, using identical machines and measures in all countries, every 5 weeks from 14 gestational weeks to delivery. Five growth measures studied were head circumference, biparietal diameter, occipitofrontal diameter, abdominal circumference, and femur length.

"In one part of a city or country a fetus or newborn can be judged as small, but a healthy size in another," senior author Stephen Kennedy, MD, professor of reproductive medicine at the University of Oxford, said in the news release. "This can lead to inaccurate diagnosis and ultimately unnecessary, or a lack of appropriate, treatment."

Size Standards Based on Gestational Age

The Newborn Cross-Sectional Study analyzed data from 20,486 babies born between 33 and 42 weeks' gestation to healthy mothers selected using identical criteria as in the fetal growth study. Using identical equipment in all countries, centrally trained teams performed anthropometric measurements within 12 hours of birth to develop new international centiles for weight, length, and head circumference.

"These new standards allow, for the first time, international comparisons of newborn size from 33 to 42 weeks' gestation, complementing the existing [World Health Organization] Child Growth Standards, which start at birth but do not differentiate according to gestational age," Dr. Villar said in the news release. "From now on, international standards can be used worldwide to make judgments on growth and size from conception to 5 years."

The international community should endorse these new growth charts, according to Ola Didrik Saugstad, MD, PhD, professor of pediatrics at the University of Oslo in Norway, who wrote an accompanying comment.

These newborn growth charts "are essential to guide clinical practice and could become a basic way to promote global child health," Dr. Saugstad writes. "[T]he charts show that previously recorded geographical differences in fetal growth are caused mainly by different environments."

Dr. Saugstad concludes, "[They] could become a valuable method to identify non-optimum conditions for the newborn infant. Surveillance of a child's somatic growth against a reference standard can assess child health and development."

Dr. Saugstad explained that early recognition of deviation from the standard could detect stunting or overweight at birth, which might also help identify risk for adult disease and/or obesity.

In 2012, approximately 15% of babies born worldwide (more than 20 million) had low birthweight (<2500 g). Subsequent complications included impaired immune function, higher risk for infant and childhood morbidity and mortality, and higher risk for diabetes and cardiovascular disease in adulthood.

The Bill & Melinda Gates Foundation funded these studies. Dr. Papageorghiou has received personal fees from Intelligent Ultrasound and nonfinancial support from Philips Ultrasound. One coauthor has received a subcontract for the INTERGROWTH-21st Project from Oxford University. Another coauthor has received personal fees from Intelligent Ultrasound and grants and nonfinancial support from Philips Ultrasound. The other authors have disclosed no relevant financial relationships.

Lancet. 2014;384:833-835, 857-879. Fetal Growth Longitudinal Study abstract, Newborn Cross-Sectional Study abstract, Comment extract

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