birthThere is up to a five-fold increased risk of severe perineal tearing during childbirth in women who had such a tear in a previous delivery, according to a new study from the London School of Hygiene and University of Manchester.

The study of nearly 640,000 mothers investigated those who have had a third or fourth degree perineal tear to identify the importance of the mode of delivery in subsequent pregnancies and the recurrence of severe perineal tears.

Most women tear to some extent during childbirth and in some women the tear may be more extensive. In England, the rate of reported severe perineal tears has tripled from 1.8% to 5.9% between 2000 and 2012.

Results show that the prevalence of third or fourth degree tearing at first birth for the cohort was 3.8%. Among women who had a third or fourth degree tear at first birth, 24.2% were delivered by elective caesarean section, compared with 1.5% of women who did not tear at first birth.

Dr Leroy Edozien, a consultant obstetrician at UoM and co-author of the study said: “Our study shows that the relative risk of a repeat tear is a five-fold increase and the absolute risk of a repeat tear is about 7 in 100. Clinicians should communicate both the relative and the absolute risk when discussing mode of delivery with women who suffered a severe tear in their previous pregnancy.”

National guideline on mode of delivery
Furthermore, the report found that among women who had a vaginal delivery at second birth, the rate of a severe tear was 7.2% in women with a tear at first birth, compared to 1.3% in women without, a more than five-fold increase in risk.

Other risk factors to increase the risk of third and fourth degree tearing at second birth include; high birth weight, forceps delivery and the presence of shoulder dystocia. Additionally tearing was higher in older women, women living in the least deprived communities and in Asian women, notes the report.

Commenting on the findings, the RCM's midwifery advisor Jane Munro said: “This study confirms the findings of previous studies about the risks of perineal tearing during childbirth for women who have a severe tear in a previous birth. Consequently, it will add to the vital information that needs to be discussed with a mother when planning her next birth.

"As the study's authors suggest, work on a national guideline about the best mode of delivery for the next birth for these women. It also would be helpful to gain agreement, and standards, from health professionals about all the risk factors and possible complications for the different types of delivery options for these mothers. This all needs to be part of the important discussion between the maternity team and the mother.”

Watch highlights of Dr Nigel Atherton discussing the risks and impacts of perineal trauma alongside possible treatments at JFHC Live 2014: