Estimates of weight-for-height status are affected if one or more limbs are missing (a visual impression should be sufficient), but changes in weight are unlikely to be affected if there is no change in any prosthetic device used. (A typical prosthesis weighs approximately 3 to 5 lb [1.5 to 2.5 kg].)
The most accurate method is to measure height before pregnancy or as early in the pregnancy as possible to reduce errors caused by changes in posture. Use a stadiometer, either one constructed at the health center or a commercial one that is not built into a weighing scale. Push the vertical board flat against the wall and lower it along the metal measuring tape until the horizontal board touches the woman's scalp. A less accurate method (but one that is better than self-reported height) is to use a stadiometer that is built into a weighing scale.
To help achieve consistent, accurate measurements by different staff members, four additional steps are recommended:
Zero the scale daily.
Calibrate the scale regularly (about once a month). Record the amount of drift.
Provide in-service training concerning standard procedures for measuring weight and height.
Monitor measurement techniques regularly.
Substantial weight gain is recommended during pregnancy, as shown in the weight gain grid in Tab 1.