ArticlesThe 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
Introduction
Many populations are exposed to adverse environmental conditions and inadequate nutritional intakes that affect fetal growth.1 Therefore, findings of an increased number of newborn babies small for gestational age in these geographical areas and in immigrants in ethnically heterogeneous populations in developed countries (eg, Netherlands2 and the USA3) are not surprising. However, investigators have attributed the high rates of small for gestational age newborn babies reported in certain populations to genetic factors,4 despite findings from epidemiological and clinical studies that have consistently shown similar growth patterns across some ethnic groups in infants and children from affluent, well-nourished and geographically diverse backgrounds.5, 6
Up to now, the strongest scientific evidence supporting the notion, first proposed by Habicht and colleagues,7 that both infant and child growth are more affected by health, socioeconomic status, and environmental conditions than by ethnic differences, has been provided by the multiethnic WHO Multicentre Growth Reference Study (MGRS) of healthy, breastfed children with minimum environmental, health, and nutrition constraints on growth from six populations in Brazil, Ghana, India, Norway, Oman, and the USA (n=8406).8, 9 Results of the study showed striking similarity in linear growth in children from the six sites,10 thereby justifying pooling data to construct one international growth standard from birth to 5 years of age, which has since been adopted worldwide.11, 12
Although ample data have contributed to devising international growth standards for infants and children, so far, the data for fetal growth and newborn size have been limited. The conclusions of two recent systematic reviews13, 14 strongly support the need to develop international standards to assess growth patterns in the prenatal and neonatal periods. Therefore, our aim was to assess fetal growth and newborn size across different populations by mapping skeletal growth as a continuous process from after conception to birth in a prospective, population-based project. We used identical methods in eight geographically diverse urban areas in which mothers' health and nutritional needs were met; sanitation practices and the environment were judged not to be constraining growth; and adequate, standardised antenatal care was provided. If the data generated were consistent with the WHO MGRS standards (birth to 5 years), a global set of international fetal and newborn standards could be generated to allow growth to be monitored from the post-conception period to childhood.
Section snippets
Study design and participants
INTERGROWTH-21st was a multicentre, multi-ethnic, population-based project, done between April 27, 2009, and March 2, 2014, in eight study sites: the cities of Pelotas (Brazil), Turin (Italy), Muscat (Oman), Oxford (UK), and Seattle (USA); Shunyi County, Beijing (China); the central area of Nagpur (India); and the Parklands suburb of Nairobi (Kenya).15 Its main aim was to study growth, health, nutrition, and neurodevelopment from less than 14 weeks of gestation to 2 years of age, with the same
Results
Between April 27, 2009, and Aug 2, 2013, in FGLS, we screened 13 108 pregnant women attending the study clinics; of these, 4607 (35%) who met the eligibility criteria15 consented and were enrolled (figure 1). The most common reasons for ineligibility were maternal age younger than 18 years or older than 35 years (915, 11%), maternal height less than 153 cm (1022, 12%; mostly in India and Oman), and BMI of 30 kg/m2 or higher (1009, 12%; mostly in the UK and USA). The contribution of each site to
Discussion
We have presented data obtained under rigorously controlled methods, comparing fetal skeletal growth and newborn baby and infant sizes from 9 weeks of gestation to birth, in healthy, well nourished women living in environments with minimal constraints on fetal growth, across eight geographically diverse urban areas worldwide (panel). We selected fat-free mass (ie, skeletal) indicators as the primary measurements to compare fetal growth and newborn size across the study sites. These measurements
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