The aim of this study was to establish the predictive role of obstetric variables for obstetric outcomes and birth related levator ani muscle (LAM) trauma.
In this prospective study, women underwent 3-dimensional pelvic floor ultrasound at their first appointment at 36 weeks and also 3 months postpartum. The measurements included minimal levator hiatus circumference (MLHC) and the ratio of fetal head circumference to MLHC = head-induced stretch ratio (HISR) as an indicator of the discrepancy between passage and passing canal. To derive the true impact of baby's mass on the levator ani musculature, we devised the levator ani stretch ratio (LASR), which was calculated by multiplying the HISR and the baby's weight.
Data set of 173 women was available for analysis. Mean HISR and LASR values were statistically different across all binary outcome categories, with 1 exception for HISR and levator ani injury. The odds ratios for LASR indicated positive and statistically significant associations with all obstetric outcomes examined. The probability of the LASR correctly classifying those with the adverse obstetric outcome, as estimated by the area under the curve, ranged from 0.64 to 0.80 with the strongest discriminatory ability observed for severe LAM trauma.
Fetal head circumference/mother MLHC ratio (HISR) is associated with longer length of second stage of labor, assisted delivery, and increased severity of perineal trauma. Similar associations were observed for LASR, but in addition, LASR had good discriminatory ability to identify severe LAM trauma.
Fetal head circumference/mother minimal levator hiatus circumference ratio is associated with longer length of second stage of labor, assisted delivery, and increased severity of perineal trauma.
From the *Department of Obstetrics and Gynecology, Virginia Commonwealth University Inova Fairfax Campus, Falls Church, VA; †Department of Epidemiology and Biostatistics, The University of Oklahoma Health Sciences Center, Oklahoma City, OK; and ‡Department of Obstetrics and Gynecology, Croydon University Hospital, Croydon, United Kingdom.
Reprints: S. Abbas Shobeiri, MD, Department of Obstetrics and Gynecology, Virginia Commonwealth University Inova Fairfax Campus, 3300 Gallows Road, Falls church, VA 22402. E-mail: Abbas.Shobeiri@inova.org.
The authors have declared they have no conflicts of interest.
Dr Peck was funded by a National Institutes of Health grant, and Dr van Delft was funded by the Mayday Childbirth Charity Fund.