Slowing delivery of the infant's head and instructing the mother not to push during passage of the head reduces the incidence of anal sphincter ruptures by about 70%, according to the results of a recent interventional cohort study.  

Researchers from Norway studied over 12,000 vaginal deliveries occurring over a 5-year period. Slowing delivery of the infant's head by keeping a hand on it when it is crowning and by instructing the mother not to push as the head is delivered reduced the rate of anal sphincter tears from 4.03% to 1.17% (

<.001). The reduction was similar for instrumental deliveries (16.26%–4.90%; 

<.001) and for noninstrumental deliveries (2.70%–0.72%; 

Only one 4th-degree tear occurred during the 18-month study period versus the 10, 13, and 11 that occurred per year during the period 2002 through 2004. And while the number of episiotomies increased from 13.9% in the years 2002 to 2004 to 23.1% during the first 9 months of the study period, the rate decreased to 21.1% during the last 9 months of the study.  

Commentary by Sharon T. Phelan, MD,Professor of Obstetrics and Gynecology,University of New Mexico, Albuquerque.

Dr. Laine and associates approach theprevention of 4th-degree lacerations by avoidingactive maternal effort as the head crowns anddelivers as well as the use of a medial lateralepisiotomy (>20% rate). This is a differentapproach than currently encouraged in the USwith the avoidance/minimization of the use ofany episiotomy. The combination of the slowerrate of delivery with perineal support andavoidance of midline episiotomies is useful inprevention of 3rd- and 4th-degree lacerations.On a personal note, I would also encourage asimilar control of delivery speed or providingperineal support with the delivery of theposterior shoulder. I have found that to be thesource of a large laceration after a beautifullycontrolled delivery of the vertex.

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Slower delivery of the infant's head and no pushing reduces anal sphinter ruptures.