A Case-control Study Of Risk Factors In Obstetrical Brachial Plexus Palsy

Objective:To study the determinants of obstetric brachial plexus palsy(OBPP).Methods:Forty-six newborn infants with OBPP were recruited between January1997and December2009from Technical Appraisement Center for Medical Malpractice of Shandong province as OBPP group. In the controlled group, one hundred and thirty-eight newborn infants who were deliveried in the same time, same hospital and same gender were collected according to1:3.This is a retrospective case-control study. The factor of newborn, maternal, childbirth data and work experience of midwives were analyzed by univariate and multivariate logistic regression analysis.Results:1. External pelvimetries of the two groups are within normal range, all the singleton newborns were deliveried through vagina in cephalic presentation. Twenty-two patients had left unilateral palsies, and the other twenty-four patients had right unilateral palsies. The number of the whole, upper and fore arm type is17,26and3,respectively.The maternal age, pregnancies,parity and gestational weeks are higher in OBPP group compared to the controlled group (P<0.05).2. The maternal antepartum body mass index (BMI)[(29.5±2.4)Kg/m2], height of the uterus [(34.9±2.4)cm] and abdominal circumference [(104.6±5.6)cm] in OBPP group are much higher than those in the controlled group [(26.1±2.5) Kg/m2,(33.7±2.2) cm and (98.5±5.2) cm, respectively],P<0.05.The newborn birth weight in OBPP group [(4390±489) g] is significantly higher compared to the controlled group [(3404±360)g](P<0.01).The work experience of midwives in OBPP group [(5.2±2.3)年] is more insufficient compared to the controlled group [(8.9±5.4)年], and the diference is conspicuous (P<0.01).3. There is a higher proportion of instrumental delivery,uterine atony, prolonged second stage and fetal malposition in the OBPP group compared to the controlled group,28.3%vs3.6%,28.3%vs6.5%,8.7%vs0.7%,and10.9%vs2.9%, respectively(P<0.05).4. Univariate logistic analysis shows that the P values of maternal age, antepartum BMI, height of uterus, abdominal circumference, newborn birth weight, pregnancies, second stage, instrumental delivery, fetal malposition, uterine atony and work experience of midwives are all less than0.10. Meanwhile, the work experience of midwives is a protective factor.5. The factors listed above are taken as variables, selected stepwise regression for multivariate logistic regression analysis. Boundary values are0.10. It shows that the antepartum BMI(OR=1.733) and newborn birth weight(OR=1.004) are related with OBPP(P<0.05). At the same time, the first OR is higher than the latter, therefore, the signifcance of maternal antepartum BMI is much higher than birth weight.Conclusions:1.The maternal antepartum BMI is the most important risk factor for OBPP.2.The another determinant for OBPP is newborn birth weight.3.The work experience of midwives is a protective factor.