About the WHO Fetal Growth Charts
The WHO Fetal Growth Charts were published in 2017 by Kiserud and colleagues in PLOS Medicine. They give centiles for fetal biometry and estimated fetal weight from 14 to 40 weeks, based on a longitudinal study in ten countries. This site uses these references for its centile curves.
How the study was done
| Feature | WHO Fetal Growth Charts study |
|---|---|
| Design | Prospective, longitudinal (the same fetuses scanned repeatedly) |
| Participants | 1,387 women with low-risk singleton pregnancies; 1,362 included in the growth analysis |
| Countries | Argentina, Brazil, DR Congo, Denmark, Egypt, France, Germany, India, Norway, Thailand |
| Dating | First-trimester ultrasound between 8+0 and 12+6 weeks |
| Scan schedule | Seven scans at about 14, 18, 24, 28, 32, 36 and 40 weeks |
| Parameters | BPD, HC, AC, FL, humerus length and EFW (Hadlock formula using HC, AC and FL) |
| Centiles published | 2.5th, 5th, 10th, 25th, 50th, 75th, 90th, 95th and 97.5th |
Because the same fetuses were followed over time, the study describes how fetuses grow, not only how big fetuses are at a given week. The authors also reported that growth varied between countries and was influenced by fetal sex and maternal factors such as age, height, weight and parity.
How the centile curves are generated
The study fitted quantile regression on the logarithm of each measurement, smoothed with polynomial functions of gestational age. In simple terms, each centile line is a smooth mathematical curve:
This site draws each curve from its published coefficients and checks the result against the WHO tables. For example, the WHO table gives a 50th-centile EFW of 3,617 g at 40 weeks, and this site's curve gives 3,616.7 g.
Which centiles are shown here
The charts on this site show the 5th, 25th, 50th, 75th and 95th centiles. The 25th, 50th and 75th lines divide the population into quartiles, which helps you see crossing of centiles over time. The 3rd and 10th centiles, which some clinical definitions use, are not drawn.
WHO, INTERGROWTH-21st and Hadlock: why charts differ
Several fetal growth references are in use, and they do not give identical centiles for the same measurement:
- WHO Fetal Growth Charts (2017): multinational, low-risk population, with country variation reported.
- INTERGROWTH-21st: a multinational prescriptive standard from selected healthy, well-nourished urban populations.
- Hadlock and other older charts: single-centre references, often cross-sectional, still built into many ultrasound machines.
- Local or customised charts: adjusted for a specific population, or for maternal characteristics.
The same fetus may be on the 8th centile on one chart and the 12th on another. No chart is "wrong", but mixing them within one pregnancy causes confusion. Choose one reference, ideally the one your unit or national guideline recommends, and use it consistently.
Is this an official WHO tool?
No. Fetal Growth Chart is an independent implementation of the published WHO reference. It is not produced, endorsed or reviewed by the World Health Organization. See the Disclaimer.
References
- Kiserud T, Piaggio G, Carroli G, et al. The World Health Organization Fetal Growth Charts: a multinational longitudinal study of ultrasound biometric measurements and estimated fetal weight. PLOS Med. 2017;14(1):e1002220. doi:10.1371/journal.pmed.1002220