Objective To evaluate intrapartum risk factors for anal sphincter tear.Design A prospective observational study.Setting Delivery unit at the University Hospital in Goteborg, Sweden.Participants 2883 consecutive women delivered vaginally during the period between 1995 and 1997.Information was obtained from patient records and from especially designed protocols which were completed during and after childbirth. Main outcome measuresAnal sphincter (third and fourth degree) tear.Results Anal sphincter tear occurred in 95 of 2883 women (3.3%). Univariate analysis demonstrated that the risk of anal sphincter tear was increased by nulliparity, high infant weight, lack of manual perineal protection, deficient visualisation of perineum, severe perineal oedema, long duration of delivery and especially protracted second phase and bear down, use of oxytocin, episiotomy, vacuum extraction and epidural anaesthesia. After analysis with stepwise logistic regression, reported as odds ratio, 95% confidence interval, the following factors remained independently associated with anal sphincter tear: slight perineal oedema ( Analysis of variance showed that manual perineal protection had a stronger influence on lowering the frequency, and lack of visualisation of perineum and infant weight had a stronger influence on raising the frequency, of anal sphincter tears in nulliparous compared with parous women.Conclusions Perineal oedema, poor ocular surveillance of perineum, deficient perineal protection during delivery, protracted final phase of the second stage, parity and high infant weight all constitute independent risk factors for anal sphincter tear. Such information is essential in order to reduce perineal trauma during childbirth.

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ObjectiveDesign Blind controlled trial with cross-over design.Setting Giiteborg and Skovde, Sweden.Participants One hundred healthy female volunteers. MethodsTo investigate whether, during injections of sterile water, there is any difference in perceived pain between intracutaneous and subcutaneous injections.The women were randomised into two groups and subjected to two trials, within one week of each other. During the first trial one group (n = 50) received the intracutaneous injection first, followed by the subcutaneous injection. The second group (n = 50) was given the subcutaneous injection first, followed by intracutaneous injection. In both groups all the injections were given in reverse order during the second trial. Main outcome measuresExperienced pain during the administration of sterile water injections, measured by visual analogue scale. ResultsThe analysis showed intracutaneous injections to be significantly more painful than subcutaneous injections, even after adjusting for injection day and for lefvright site of injection (mean 60.8 vsThe findings suggest that the less painful subcutaneous injection technique should be used. 41.3, P c 0.001). Conclusions

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Objective-To test the hypothesis that opiate addiction in adults might stem partly from an imprinting process during birth when certain drugs are given to the mother. Results-In subjects who had subsequently become addicts a significant proportion of mothers had received opiates or barbiturates, or both, compared with unmatched siblings (25% v 16%, X2=5 83, df= 1, p=002), and these mothers had received nitrous oxide for longer and more often. After controlling for hospital of birth, order of birth, duration of labour, presentation other than vertex, surgical intervention, asphyxia, meconium stained amniotic fluid, and birth weight the relative risk for offspring subsequently becoming an adult opiate addict increased with the number of administrations of any of the three drugs. When the addicts were matched with their own siblings the estimated relative risk was 4-7 (95% confidence interval 1-8 to 12-4, p for trend=0-002) for three administrations compared with when no drug was given.Conclusions-The results are compatible with the imprinting hypothesis. Therefore, for obstetric pain relief meth3ds are preferable that do not permit substantial passage of drugs through the placenta.