Standard methods based on last menstrual period dates misclassify and overestimate US preterm births

C. S. Ambrose, H. Caspard, C. Rizzo, E. C. Stepka, G. Keenan

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Objective:To compare number of US preterm births based on obstetric versus last menstrual period (LMP) estimates and evaluate their correlations with clinical risk indicators associated with prematurityStudy Design:Preterm births were assessed from LMP, per standard practice, and, separately, from obstetric estimates using the 2012 Natality Public Use File. Percentages of infants with neonatal intensive care unit (NICU) admission and low birth weight (LBW) were calculated.Result:More births were <37 weeks gestational age (GA) by reported LMP (11.4%) versus obstetric estimates (9.5%). Among infants preterm by LMP, but born at 37-41 weeks by obstetric estimates, there were 5.7% NICU admission and 7.7% LBW rates versus 25.2% and 35.4%, respectively, of those preterm by obstetric estimates but born 37-41 weeks by LMP assessments.Conclusion:Obstetric estimates provide the most clinically relevant estimates of US preterm births. Assessments calculated from LMP alone may overestimate prematurity incidence by ∼20%.

Original languageEnglish (US)
Pages (from-to)411-414
Number of pages4
JournalJournal of Perinatology
Issue number6
StatePublished - Jun 28 2015

Bibliographical note

Funding Information:
Medical writing assistance was provided by John E. Fincke and Anny Wu of Complete Healthcare Communications, Inc., (Chadds Ford, PA, USA) and funded by MedImmune. This study was sponsored by MedImmune.

Publisher Copyright:
© 2015 Nature America, Inc. All rights reserved.


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