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30-10-2011 | Gynaecology | Article

Recurrence risk is high after obstetric anal sphincter injury


Free abstract

MedWire News: Women who experience obstetric anal sphincter injuries (OASIS) during their first vaginal delivery are at high risk for recurrence during second and third subsequent deliveries, report Norwegian researchers.

However, OASIS during a first delivery does not negatively impact whether these women go on to have a subsequent delivery, they add, in BJOG: An International Journal of Obstetrics and Gynecology.

The findings mean that "emphasis should be placed on counseling women after an initial OASIS and attention should be paid to prevent OASIS in the first delivery," write Elham Baghestan (Haukeland University Hospital, Bergen) and colleagues.

Little is known about OASIS recurrence rates and subsequent delivery rates after OASIS in first delivery, so the team investigated these outcomes as well as factors including paternal influence and delivery method in data encompassing all births in Norway from 1967 through 2004 (n=828,864).

All births were singleton, of vertex presentation, and all infants weighed 500 g or more. OASIS occurred in 2.8%, 1.1%, and 0.7%, of first, second, and third vaginal deliveries, respectively.

After adjusting the analysis for year of delivery, birth weight, instrumental delivery, and size of maternity unit, results revealed a significant 4.2-fold increased risk for OASIS in second deliveries subsequent to first deliveries with OASIS, with absolute rates of 5.6% versus 0.8%, respectively.

Previous OASIS also increased the risk for women who had three children, with a significant 9.3- and 10.6-fold increased risk for women with OASIS in the second only, and both the first and second deliveries, respectively.

Interestingly, the researchers observed that men who fathered children whose births resulted in OASIS were a significant 2.1 times more likely than men with no history of OASIS, to father future children, with different women, whose births involve OASIS.

However, if the deliveries happened in different maternity units, the paternal-related recurrence risk was not significantly increased.

More women without previous OASIS went on to have a second child compared with women who had OASIS during their first delivery, at 76.9% versus 66.7%, although the difference was nonsignificant, note the researchers.

After adjustment for potentially confounding factors, women with OASIS in their first delivery were significantly more likely to have a planned cesarean for their second deliveries, with rates of 6.0% versus 1.5%.

Although most women who sustained OASIS in their second and third deliveries did not have a previous OASIS, say the researchers, as many as 10% of all cases of OASIS in the second delivery, and 15% of cases of OASIS in the second delivery, were attributable to a history of OASIS.

The finding of a potential paternal effect on OASIS warrants further study, they suggest.

MedWire ( is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Sarah Guy

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