Clinical estimation of fetal weight and the Hawthorne effect
Received 2 January 2008; received in revised form 16 July 2008; accepted 19 July 2008. published online 26 August 2008.
Abstract
Objective
The Hawthorne effect refers to improvement in performance solely due to the subject's knowledge that he or she is being studied. We sought to determine if an obstetrician's clinical estimation of fetal weight (EFW) is influenced by the Hawthorne effect seen in some clinical trials.
Study design
We compared obstetricians’ clinical EFW's obtained during a study period to those obtained prior to the study period in one institution. We included any patient presenting at ≥37 weeks gestation. We excluded multiple pregnancies and patients with a recent sonographic EFW.
Results
There was no difference in regards to the proportion of EFW's within 10% of the birthweight (67.9% vs. 68.5%, p=.91), the mean absolute difference of EFW-birthweight (282±227g vs. 285±232g, p=.88), or the mean absolute percent error (8.5±7.4% vs. 8.6±7.2%, p=.96). We also could not find any Hawthorne effect when we excluded resident physicians’ EFW's and when we analyzed the subgroup of newborns with a birth weight ≥4000g.
Conclusion
An obstetrician's knowledge that he or she is being studied is unlikely to improve clinical EFW accuracy. Published clinical EFW accuracies are likely to be similar to those obtained in clinical practice.
aDepartment of Obstetrics and Gynecology (NSF, STC), Weill Cornell Medical College, New York, NY, USA
bDepartment of Public Health (JSB), Weill Cornell Medical College, New York, NY, USA
Corresponding author at: Maternal Fetal Medicine Associates, PLLC, 70 East 90th Street, New York, NY 10128, USA. Tel.: +1 212 722 7409; fax: +1 212 722 7185.
ABSTRACT