[A case-control study on the risk factors related to obstetric brachial plexus palsy]

Abstract

Objective: To identify the risk factors and related degrees associated to obstetric brachial plexus palsy(OBPP).

Methods: A case-control study was performed. Neonatal records of thirty-one cases with OBPP and their corresponding maternal records from the Department of Gynecology and Obstetrics of eight hospitals in Shanghai city from 1988 to 2002 were reviewed. Four controls, all living in Shanghai were selected to match each case and were born within the same year at the same hospital. The control group also included 124 cases without OBPP. According to the uniformed data and tables used were from medical records and from pregnant women. Epidemiological study was carried out on both case group and control group. Variables for analyses would include: (1) race, age, height, family history, pre-pregnancy weight, body mass index at the pre-pregnancy (weight/height2) on those pregnant women as well as on parity of their mothers; (2) the process of delivery which includeing clinic pelvis evaluation, height of uterus, abdomen circumference,antepartum weight,body mass index before delivery, mode of delivery,the duration of active phase and 2nd stage of labor, shoulder dystocia; (3) on neonates: sex, gestational age, birth weight,affected limb, Apgar scores of 1 and 5 minutes, other birth trauma and resuscitation of infant. Statistical tests applied to these data would include Student's T test for continuous variables and chi2 analysis for discrete data. Risk calculation of OBPP was performed by univariable and multivariable conditional logistic regression analysis.

Results: 12 factors related to expsure were identified for OBPP through univariable conditional logistic regression analysis. When multivariable conditional logistic regression model at P = 0.1 was applied, four factors such as cesarean (OR = 0.060), forceps (OR = 65.237), birth weight (OR = 35.468), and pre-pregnancy body mass index (OR = 23.901) were selected.

Conclusion: Forceps delivery,macrosomia, and increase of pre-pregnancy body mass index (> or = 21) were risk factors of OBPP in the order of degrees to risk while cesarean seemed to serve as a protective factor.