Errors in birth registrations and coding of twins and higher order multiples.

Area of Science:

• Reproductive Medicine
• Perinatology
• Medical Statistics

Background:

• Monozygotic (identical) twins have higher risks of fetal/infant death and morbidity than dizygotic (fraternal) twins.
• Accurate zygosity assignment is crucial for risk stratification and parental counseling.
• Misclassification of zygosity can arise from errors in registering the sex and number of fetuses in multiple pregnancies.

Purpose of the Study:

• To validate the accuracy of coding and registration for the number and sex of births in multiple maternities.
• To assess the reliability of zygosity assignment based on registered sex in twin births.

Main Methods:

• Analysis of fetal and infant death registrations for multiple maternities in England and Wales (1993-1998).
• Examination of registered sex and number of fetuses against death certificate information for discrepancies.
• Inclusion of data on twin, triplet, and higher-order multiple births.

Main Results:

• Significant discrepancies were found in the registration of sex for fetuses of indeterminate sex.
• Cases registered as different-sex twins were not exclusively dizygotic, indicating potential misclassification.
• Inconsistencies between the number of infants registered at birth and the number mentioned on registration certificates were observed.

Conclusions:

• It cannot be assumed that multiple births with different registered sexes are dizygotic.
• Inaccurate sex assignment has significant implications for parental counseling regarding risks of infant death and morbidity.
• Errors in registration have medico-legal relevance when assessing negligence in cases of infant morbidity.