A large study led by researchers at Oxford University in the UK, and funded by the Bill & Melinda Gates Foundation, finds that it is varying levels of nutrition and health that account for global disparities in newborn size – not race, as previously thought.
In 2010, an estimated 32.4 million babies in low- and middle-income countries – accounting for about 27% of all global live births – were born undernourished.
Birth size is a significant health concern, as small babies have a close association with death in infancy and childhood. There are also serious short- and long-term health consequences, such as diabetes, high blood pressure and heart disease.
There are wide disparities between the average size of babies born in different parts of the world, which led scientists to assume that ethnicity may influence babies’ growth in the womb and size when they are born.
The INTERGROWTH-21st study examined almost 60,000 pregnancies across Brazil, China, India, Italy, Oman, the UK and the US. The researchers measured the bone growth of these babies in the womb using ultrasound and also measured the babies’ length and head circumference at birth.
The researchers found that the care provided during pregnancy and the educational, health and nutritional status of the mothers have greater influence over the size of babies than race or ethnicity.
If these factors are equally good, the researchers say, babies have equal chances of healthy growth in the womb and having future good health.
Prof. Jose Villar of the Nuffield Department of Obstetrics & Gynaecology, University of Oxford, says:
“Currently we are not all equal at birth. But we can be. We can create a similar start for all by making sure mothers are well educated and nourished, by treating infection and by providing adequate antenatal care.
Don’t tell us nothing can be done. Don’t say that women in some parts of the world have small children because they are predestined to do so. It’s simply not true.”
The study also tackles one of the main problems with improving pregnancy outcomes, which is that at least 100 different growth charts are used in clinics around the world to assess fetal growth and newborn size.
“This is very confusing for doctors and mothers and makes no biological sense. How can a fetus or a newborn be judged small in one clinic or hospital and treated accordingly, only for the mother to go to another city or country, and be told that her baby is growing normally,” says Prof. Stephen Kennedy of the University of Oxford, one of the senior authors of the paper.
INTERGROWTH-21st used the international growth standards from the World Health Organization’s (WHO) Multicentre Growth Reference Study.
The mean length at birth of the newborns in the INTERGROWTH-21st study was 49.4 ± 1.9 cm, compared with 49.5 ±1.9 cm in the WHO infant study.
“The INTERGROWTH-21st results fit perfectly with the existing WHO Infant and Child Growth Standards,” says one of the study’s lead investigators, Prof. Ruyan Pang, from Peking University, China.
“Having international standards of optimal growth from conception to 5 years of age that everyone in the world can use means it will now be possible to evaluate improvements in health and nutrition using the same yardstick.”
The final aim of the study is to construct new international standards – taking into account health, nutrition and socioeconomic status – that will describe the optimal growth of a baby both in the womb and as a newborn.
“The fact that when mothers are in good health, babies grow in the womb in very similar ways the world over is a tremendously positive message of hope for all women and their families,” says the Chair of the Steering Committee of the global research team, Prof. Zulfiqar Bhutta.
“But there is a challenge as well. There are implications in terms of the way we think about public health: this is about the health and life chances of future citizens everywhere on the planet. All those who are responsible for health care will have to think about providing the best possible maternal and child health.”