The influence on a 'normal' birthweight distribution of a minor population of growth retarded infants: a Monte Carlo simulation

Impaired growth and risk of fetal death: is the tenth percentile the appropriate standard?

OBJECTIVE

Our purpose was to determine whether the 10th percentile of birth weight for gestational age is appropriate to identify fetuses at risk of death associated with impaired growth.

STUDY DESIGN

All live births recorded in Virginia from Jan. 1, 1991, through Dec. 31, 1993, were examined. Percentile growth curves were constructed, and fetal, neonatal, and perinatal mortality rates were calculated for births within various percentile intervals.

RESULTS

Significantly elevated fetal mortality was found for birth weights through the 15th percentile. The odds ratio for fetal mortality relative to the baseline for births < or = 5th percentile was 5.6, for the 5th through the 10th percentile 2.8, and for the 10th through the 15th percentile 1.9. These were all significant.

CONCLUSION

Fetuses with birth weights between the 10th and 15th percentiles are at a significantly increased risk for fetal death. Therefore the use of the 15th percentile as a diagnostic threshold for the identification of the fetus at increased risk associated with impaired growth is recommended.