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Customised assessment of fetal growth potential: implications for perinatal care
  1. Jason Gardosi
  1. Correspondence to Jason Gardosi, West Midlands Perinatal Institute, Birmingham B6 5RQ, UK; jason.gardosi{at}

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Twenty years since the first publication of the concept of customised fetal growth charts,1 this may be an opportune time to reflect on its current and potential role in perinatal care.

The customised standard defines the individual fetal growth potential by three underlying principles. It is,

  1. adjusted to reflect maternal constitutional variation;

  2. optimised, by presenting a standard free from pathological factors such as diabetes and smoking; and

  3. based on fetal weight curves derived from normal pregnancies, rather than neonatal weight curves which include pathological preterm deliveries.

Thus the standard strives to predict the weight to be reached in an uncomplicated pregnancy, and to detect if it has deviated from the norm due to pathological influences. In practice, software calculates a ‘term optimal weight’ (TOW) adjusted for maternal characteristics such as height, weight, ethnic group and parity, as well as the baby's sex if known. TOW is combined with a standard ‘proportionality’ function2 using Hadlock's fetal weight distribution3 to provide a gestation-related optimal weight (GROW) curve4 ( (figure 1).

Figure 1

(A, B) Examples of customised charts using GROW (Gestation-Related Optimal Weight, software v. 7.5.1, The charts can be used to plot previous baby weights and ultrasound estimated fetal weights in the current pregnancy (right Y axis) as well as fundal height measurements for serial assessment (left Y axis). The horizontal axis shows the day and month of the start of each week of gestation, calculated by the software on the basis of the estimated date of confinement. The three curves on the chart are the 50th centile and the 10th and 90th centile limits, representing the predicted range of optimal growth for each pregnancy, after adjustment for maternal height, weight, parity and ethnic origin. The pregnancy details are shown on the top left of the chart, …

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