Baylor University Medical Center Proceedings April 2017 - 151

Perineal body length and perineal lacerations during delivery
in primigravid patients
T. Lance Lane, MD, Christopher P. Chung, MD, Paul M. Yandell, MD, Thomas J. Kuehl, PhD, and Wilma I. Larsen, MD

This study assessed the relation between perineal body length and the
risk of perineal laceration extending into the anal sphincter during vaginal
delivery in primigravid patients at an institution with a low utilization of
episiotomy. This was a prospective study of primigravid patients in active
labor. Primigravid women with singleton pregnancies who were in the
first stage of labor at 37 weeks gestation or greater were recruited, and
the admitting physician measured the length of the perineal body. The
degree of perineal laceration and other delivery characteristics were
recorded. Data were analyzed using univariate analyses, receiver-operator
curve analyses, and multiple logistic regression for factors associated
with increased severity of vaginal lacerations. The perineal body length,
duration of second stage of labor, type of delivery, and patient age were
associated (P < 0.1) with third- and fourth-degree (severe) perineal
lacerations in primigravid women using receiver-operator curve analysis.
Using logistic regression, only the duration of second stage of labor and
length of the perineal body were significant (P < 0.04) predictors of
third- and fourth-degree lacerations, with odds ratios of 32 (1.3 to 807
as 95% CI) and 24 (1.3 to 456), respectively. Both a perineal body length
of ≤3.5 cm and a duration of second stage of labor >99 minutes were
associated with an increased risk of third- and fourth-degree lacerations
in primigravid patients.

nal sphincter lacerations place patients at increased risk
for pelvic organ prolapse, genuine stress urinary incontinence, sexual dysfunction, and fecal incontinence (1-5).
Operative vaginal delivery, persistent occiput posterior,
and fetal macrosomia are known risk factors for anal sphincter
injury (6-9); however, there is some evidence that a shortened
perineal body may also be a risk factor for severe lacerations
(10-13). Prior studies have been confounded by high rates of
episiotomy, multiparous patients, and a retrospective design.
The aim of our study was to assess the relation of perineal body
length and other characteristics to the risk of perineal laceration
extending into the anal sphincter during delivery in primigravid
patients in an institution with a low episiotomy rate.
METHODS
Prior to the initiation of the study, approval was obtained
from the institutional review board at Scott and White, Temple,
Texas. All primigravid women with singleton pregnancies who
Proc (Bayl Univ Med Cent) 2017;30(2):151-153

were in the ﬁrst stage of labor with a gestational age of 37 and
0/7 weeks or greater were eligible for our prospective study.
Primigravids were deﬁned as women who had not carried a
pregnancy past 20 weeks gestational age prior to the current
gestation. The ﬁrst stage of labor was deﬁned as the interval
between the start of regular contractions combined with any
cervical dilatation and/or eﬀacement until a cervical dilation
of 10 cm was reached. Women with a fetal station greater than
zero were excluded. Primigravid women delivered by cesarean
and multigravid women were also excluded.
The resident physician measured the length of the perineal
body upon presentation using a form for data collection that
did not include any patient-identifying information. The perineal body length was deﬁned as the distance from the posterior
vaginal fourchette to the center of the anal oriﬁce. This measurement was taken at rest while the patient was in the dorsal
lithotomy position, using a sterile Q-tip. The measurement was
recorded to the nearest tenth of a centimeter. A diagram of the
distances measured was also included on the preprinted form.
These measurements were transcribed on the same form along
with other patient characteristics, including maternal age, race,
maternal height, maternal weight, and gestational age. After
delivery, data on the degree of vaginal laceration, oxytocin use,
length of second stage of labor, fetal presentation, fetal birth
weight, use of episiotomy, and delivery type used were recorded.
The delivering physicians, which included both residents and attending physicians, graded perineal lacerations clinically as none
or ﬁrst through fourth degree. First-degree lacerations involve
only the epithelial layer. Second-degree lacerations can extend
into the perineal body but not into the external anal sphincter.
Third-degree lacerations extend into the anal sphincter. Fourthdegree lacerations extend through the rectal mucosa.

From the Department of Obstetrics and Gynecology, Scott and White Memorial
Hospital and Clinic and Texas A&M Health Science Center College of Medicine,
Temple, Texas.
This work was presented as an oral poster at the combined national meeting
of the American Urogynecologic Society and the International Urogynecological
Association in Washington, DC, in July 2014.
Corresponding author: Wilma I. Larsen, MD, Department of Obstetrics and
Gynecology, Scott & White Health, 2401 South 31st Street, Temple, TX 76508
(e-mail: wilarsen@hot.rr.com).
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