SCOTTSDALE, ARIZ. – The extent of stretching of the perineal body during the second stage of labor is not helpful in predicting which women will experience adverse obstetric and postpartum outcomes, new data show.
Short perineal body length is known to increase the risk of severe perineal laceration at the time of delivery as well as postpartum functional disorders, noted presenting author Dr. Jill Alldredge. Maternal expulsive efforts during the second stage of labor that stretch the pelvic floor may also damage the pelvic floor muscles.
She and her colleagues performed a planned secondary analysis of the APPLE cohort (Alterations in the Pelvic Floor in Pregnancy, Labor and Ensuing Years), analyzing data from 448 nulliparous women who had a vaginal birth attended by a certified nurse-midwife, had repeated perineal measurements over time, and were followed prospectively to 12 months post partum.
On average, perineal body length increased by about 2.4 cm in the cohort between the antepartum period and the maximal length during the second stage of labor, according to data reported at the annual scientific meeting of the Society of Gynecologic Surgeons.
However, neither perineal body length nor change in this length at any time point was associated with perineal lacerations, or with urinary or anal incontinence or not being sexually active at 6 months post partum.
"We can see that the perineum is dynamic and does stretch during labor. However, measurement of the perineal body length and change in perineal body length between the antepartum, intrapartum, and post partum time periods does not predict perineal trauma or postpartum pelvic floor dysfunction," commented Dr. Alldredge, an obstetrics-gynecology resident at the University of New Mexico in Albuquerque.
APPLE participants had measurement of the perineal body length during the antepartum period, at the onset of labor, at the onset of and every 10 minutes during the second stage, and at 6 and 12 months post partum. The anal opening and the genital hiatus also were measured during the second stage of labor.
The mean perineal body length was 3.7 cm during the antepartum period, and the mean maximal perineal body length during the second stage of labor was 6.1 cm, she said at the meeting, jointly sponsored by the American College of Surgeons.
During the second stage of labor, the maximal anal opening was 2.0 cm on average. The genital hiatus had an anterior-posterior maximal diameter of 7.5 cm, a maximal transverse diameter of 4.7 cm, and a maximal introital area of 119.4 cm2.
Overall, 35% of women experienced a second-degree or worse perineal tear. And at 6 months post partum, 72% had at least mild urinary incontinence, 68% had at least mild anal incontinence, and 13% were not sexually active.
However, analyses showed that neither perineal body length nor stretch at any of the time points assessed was significantly associated with any of these outcomes.
Dr. Alldredge disclosed no relevant conflicts of interest.