Premium
Birth weight, prematurity and accuracy of gestational age
Author(s) -
Mongelli M.,
Gardosi J.
Publication year - 1997
Publication title -
international journal of gynecology and obstetrics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.895
H-Index - 97
eISSN - 1879-3479
pISSN - 0020-7292
DOI - 10.1016/s0020-7292(96)02835-4
Subject(s) - gestational age , birth weight , medicine , obstetrics , percentile , incidence (geometry) , low birth weight , gestation , preterm delivery , pregnancy , pediatrics , statistics , biology , genetics , mathematics , physics , optics
Objective: To investigate commonly used birth weight categories in relation to gestational age assignment by menstrual (LMP) or ultrasound dates. Methods: A total of 34249 cases were retrieved from the East Midlands Obstetric Database. Of these, 2281 (6.7%) delivered preterm (<37 weeks) by ultrasound dating. The percentage of preterm and post‐term cases was calculated for birth weight categories from < 1500 g to > 4499 g at 500 g intervals. The incidence of preterm delivery was estimated for birth weights from < 1500 g to 3400 g. Results: For the ‘low birth weight’ cut‐off of 2500 g, only 64% were actually preterm as assessed by ultrasound, as opposed to 59% as judged by menstrual dates. Nearly 95% of infants weighing over 3000 g are full‐term. For birth weights under 2900 g, there is a trend for LMP‐derived gestational age to underestimate preterm delivery, by up to 35.5%. By ultrasound dating, 90% of infants under 1800 g are preterm, rising to 98.2% for those under 1500 g. Conclusions: As nearly 40% of ‘low birth weight’ infants are born at term, the old classification of ‘low birth weight’ should be replaced by gestational age‐specific percentile categories. Menstrual dates systematically underestimate the prevalence of preterm delivery. Previous estimates of preterm delivery rates based on LMP data have under‐stated their true incidence.