OCCULT ANAL-SPHINCTER TRAUMA FOLLOWING RANDOMIZED FORCEPS AND VACUUM DELIVERY

Objective: To determine the prevalence of occult anal sphincter trauma 5 years after randomization to forceps and vacuum delivery. Method: A nal endosonography and manometry was performed in 44 of 313 women who had originally participated in one center of the Keele University Mult icenter Assisted Delivery Trial at the North Staffordshire Maternity H ospital between September 1989 and May 1990. Results: 50% admitted to defecatory symptoms and anal sphincter defects were identified in 61%. On the basis of intention to treat, 82% of forceps (n = 17) and 48% o f vacuum deliveries (n = 27) had occult sphincter defects (P = 0.03). In four women, both instruments were used. However, the preponderance of defects in the forceps group persisted even when analysis was perfo rmed according to the final mode of delivery as well as in the group w here only one instrument was used (n = 40). There was a significant fa ll in maximum squeeze anal pressure in the forceps group compared to t he vacuum group (56 vs. 36 mmHg; P = 0.0007). Although twice as many i n the forceps group suffered anal incontinence (32% vs. 16%) significa nce was not reached. Conclusions: Vacuum delivery appears to be associ ated with less occult anal sphincter trauma than forceps delivery. A l arge prospective randomized study is required to address the impact of specific situations, such as failed instrumentation with use of a sec ond instrument and rotational delivery. (C) 1998 International Federat ion of Gynecology and Obstetrics.