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Are reported preterm birth rates reliable? An analysis of interhospital differences in the calculation of the weeks of gestation at delivery and preterm birth rate

  1. Imelda Balchin1,*,
  2. John C. Whittaker2,
  3. Philip J. Steer1,
  4. Ronald F. Lamont3

Article first published online: 16 JAN 2004

DOI: 10.1046/j.1471-0528.2003.00026.x

Issue

BJOG: An International Journal of Obstetrics & Gynaecology

BJOG: An International Journal of Obstetrics & Gynaecology

Volume 111, Issue 2, pages 160–163, February 2004

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How to Cite

Balchin, I., Whittaker, J. C., Steer, P. J. and Lamont, R. F. (2004), Are reported preterm birth rates reliable? An analysis of interhospital differences in the calculation of the weeks of gestation at delivery and preterm birth rate. BJOG: An International Journal of Obstetrics & Gynaecology, 111: 160–163. doi: 10.1046/j.1471-0528.2003.00026.x

Author Information

  1. 1

    Academic Department of Obstetrics and Gynaecology, Imperial College Faculty of Medicine, Chelsea and Westminster Hospital, London, UK

  2. 2

    Department of Epidemiology and Public Health, Imperial College Faculty of Medicine, London, UK

  3. 3

    Department of Obstetrics and Gynaecology, Northwick Park Hospital, Harrow, Middlesex, UK

* *Dr Imelda Balchin, Academic Department of Obstetrics and Gynaecology, Imperial College Faculty of Medicine, Chelsea and Westminster Hospital, 369 Fulham Road, London SW10 9NH, UK.

Publication History

  1. Issue published online: 16 JAN 2004
  2. Article first published online: 16 JAN 2004

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We investigated the possibility of preterm birth misclassification as a determinant of variation in its reported rates. Using a database of 497,105 deliveries from 17 hospitals, the best estimate of gestational age made at delivery and entered into the database at that time was recalculated from the menstrual dates and mid-trimester ultrasound scan. The recalculated completed weeks of gestation at delivery was compared with that made at birth. Calculation of estimated gestational age varied between hospitals due to inconsistencies in ‘rounding’ and ‘truncating’ the weeks of gestation at delivery. This resulted in preterm birth misclassification rates of up to 10.1%.

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