Variation in birth timing and location of the neonatal line in human enamel.

The location of the neonatal line in 173 primary teeth from 43 children was investigated and shown to differ significantly among pre-term, term, and post-term births. Approximately 75% of the neonatal lines that lie beyond 2SD of the mean location of the line in term births are from children born outside of 38 to 42 weeks gestation. The duration of pregnancy accounts for about 36% of the variation in location of the neonatal line in non-term births. Based on the small proportion of non-term births whose neonatal line is located beyond 2SD of the mean location of the neonatal line in term births, it is estimated that this technique will provide individualizing information in about 3% of immature skeletonized remains in a forensic context. The relative timing of pre- and postnatal pathological striae in the enamel of primary teeth can be evaluated in terms of the variation, documented here, in the location of the neonatal line due to individual and birth timing differences. Determination of the timing of pathological enamel striae will aid in the identification of both children and adults for whom histological examination of enamel is undertaken.