INTERGROWTH-21st was a multicentre, multiethnic, population-based project, conducted between 2009 and 2014 in eight countries. The primary aim was to study growth, health, nutrition, and neurodevelopment from less than 14 weeks’ gestation to 2 years of age. Details of the study have been described elsewhere23 (link)–25 (link). In brief, all institutions providing obstetric care in eight geographically diverse regions in Brazil, China, India, Italy, Kenya, Oman, UK, and USA were chosen as study sites. From these, healthy women with a naturally conceived, singleton pregnancy who were at low risk of adverse maternal and perinatal outcomes were prospectively enroled into FGLS, one of the main components of INTERGROWTH-21st. GA was estimated from the LMP provided that: (a) the date was certain; (b) the woman had a regular 24–32 day menstrual cycle; (c) she had not been using hormonal contraception or breastfeeding in the preceding 2 months, and (d) any discrepancy between the GAs based on LMP and CRL, measured by ultrasound at 9+0 to 13+6 weeks from the LMP was ≤7 days26 (link).
Trained, dedicated research sonographers performed ultrasound scans every 5±1 weeks using identical equipment at all sites (Philips HD9 [Philips Ultrasound, Bothell, WA, USA] with curvilinear abdominal transducers C5–2, C6-3, V7-3). We used stored images of the three standard anatomical planes: (a) fetal head in the axial view at the level of the thalami, as required for measurement of the HC; (b) abdomen in an axial view at the level of measurement of the AC, and (c) femur in the longitudinal view used for measuring FL. The detailed measurement protocol, training, standardisation, and quality-control methods, including quality scoring of images, used across all study sites are described in detail elsewhere25 (link),27 (link),28 (link) and all documentation, protocols, data collection forms, and electronic transfer strategies are freely available on the INTERGROWTH-21st website.
Trained, dedicated research sonographers performed ultrasound scans every 5±1 weeks using identical equipment at all sites (Philips HD9 [Philips Ultrasound, Bothell, WA, USA] with curvilinear abdominal transducers C5–2, C6-3, V7-3). We used stored images of the three standard anatomical planes: (a) fetal head in the axial view at the level of the thalami, as required for measurement of the HC; (b) abdomen in an axial view at the level of measurement of the AC, and (c) femur in the longitudinal view used for measuring FL. The detailed measurement protocol, training, standardisation, and quality-control methods, including quality scoring of images, used across all study sites are described in detail elsewhere25 (link),27 (link),28 (link) and all documentation, protocols, data collection forms, and electronic transfer strategies are freely available on the INTERGROWTH-21st website.
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