Unexpected reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries during the study period: was this the Hawthorne effect? W.C. Leung * , H.S.W. Lam, K.W. Lam, M. To, C.P. Lee Objective The study was originally designed to identify the risk factors that could predict those difficult instrumental deliveries resulting in birth trauma and birth asphyxia. Design A prospective study on all singleton deliveries in cephalic presentation with an attempt of instrumental delivery over a 12-month period (13 March 2000 to 12 March 2001). Setting A local teaching hospital. Sample Six hundred and seventy deliveries. Methods A codesheet was designed to record the demographic data, characteristics of first and second stages of labour and neonatal outcome. In particular, the doctor had to enter the pelvic examination findings before the attempt of instrumental delivery. Main outcome measures Birth trauma and birth asphyxia. Results There was a significant reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries during the study period (0.6%) when compared with that (2.8%) in the pre-study period (1998 and 1999) (RR 0.27, 95% CI 0.11 – 0.70). There was more trial of instrumental deliveries in the operating theatre although this was not statistically significant (RR 1.19, 95% CI 0.88 – 1.60). The instrumental delivery rate decreased during the study period (RR 0.88, 95% CI 0.82–0.94). The caesarean section rate for no progress of labour, the incidence of direct second stage caesarean section and the incidence of failed instrumental delivery did not increase during the study period. Conclusions Apart from the merits of regular audit exercise and increasing experience of the staff, the Hawthorne effect might be the major contributing factor in the reduction of birth trauma and birth asphyxia related to instrumental deliveries during the study period. INTRODUCTION The true success of a trial of instrumental delivery is the outcome, by whatever route, of the healthiest child and mother. The true failure is not when vaginal delivery is not achieved but when avoidable injury is inflicted 1 . Our hospital is a local teaching hospital with about 4000 deliveries per year. There is a report system that every single case of birth trauma (except cephalohaematoma and clavicular fractures) and severe birth asphyxia would be reviewed by a Birth Trauma Panel. The Panel consists of two consultants, one associate professor and the chief nursing officer of the labour ward. Birth trauma is ascer- tained by the paediatrician who has attended the delivery or examined the baby afterwards. Severe birth asphyxia refers to those cases with an Apgar score on the first minute of 3 requiring admission to neonatal intensive care unit. There were altogether 30 cases of birth trauma and 13 cases of birth asphyxia related to instrumental deliveries in 1998 and 1999 in our hospital (Table 1). The 13 cases of birth asphyxia referred to those with the Birth Trauma Panel’s conclusion that the instrumental delivery was contributing to the asphyxia. The 30 cases of birth trauma included: Erb’s palsy (10 cases); fractured skull (one case); fractured skull with Erb’s palsy (one case); fractured skull with facial nerve palsy (one case); fractured skull with subaponeurotic haemorrhage (three cases); fractured skull with subapo- neurotic and subdural haemorrhage (one case); fractured skull with subaponeurotic and subarachnoid haemorrhage (one case); subaponeurotic haemorrhage (six cases); sub- aponeurotic and subarachnoid haemorrhage with facial nerve palsy (one case); subarachnoid haemorrhage (one case); sub- arachnoid haemorrhage with Erb’s palsy (one case); facial nerve palsy (one case); facial laceration (one case); and lac- eration of eyebrow (one case). Our study was originally designed to identify the risk factors that could predict those difficult instrumental BJOG: an International Journal of Obstetrics and Gynaecology March 2003, Vol. 110, pp. 319–322 D RCOG 2003 BJOG: an International Journal of Obstetrics and Gynaecology doi:10.1016/S1470-0328(03)02948-3 www.bjog-elsevier.com Department of Obstetrics and Gynaecology, Queen Mary Hospital, University of Hong Kong, China * Correspondence: Dr W. C. Leung, Department of Obstetrics and Gynaecology, Queen Mary Hospital, 102, Pokfulam Road, Hong Kong, China.