During Labor Video
Pelvic exams are used during labor
for initial assessment, measurement of progress, evaluation of fetal
presentation and position, and determining the status of fetal membranes.
During labor, several measurable
changes occur to the cervix, including cervical dilatation, effacement and
descent of the presenting part.
To watch the video,
Dilatation refers to the opening of
the cervix and is expressed in centimeters. The opening of this water bottle
is about 2 centimeters. If it were a cervix, you would say it is 2
centimeters dilated. To gain experience in accurately evaluating dilatation,
try measuring various objects and then use a centimeter ruler to check your
Effacement refers to the thickness
of the cervix, typically recorded in centimeters. If this water bottle neck
were a cervix, you would say it is two centimeters thick.
Station refers to the location of
the leading edge of the presenting part, relative to the ischial spines. If
the leading edge is even with the spines, that is called zero station. If
the leading edge is one centimeter below the spines, that is plus one
station. Plus two station means two centimeters below the spines and plus
three station is three centimeters below the spines. Minus one station means
the leading edge is one centimeter above the ischial spines.
The ischial spines are usually
easily palpated during pelvic examinations.
Serial measurements can be tracked
over time to assist in evaluating labor progress. Most labors progress
normally, but some do not, and the causes of abnormal can often be
determined from this graphical display.
Babies are usually delivered
occiput anterior facing down. Some are born occiput posterior, facing up.
This fetal position does matter since it can influence both the course of
labor and delivery.
Begin by determining whether the
presentation is cephalic or breech. The fetal skull is rounded, firm and
smooth. In contrast, the fetal breech is soft, with some bony prominences.
Feet have a distinctive feel, and hands may present with the head as a
Should you encounter a prolapsed
umbilical cord, with the cord coming before the fetal head, this is an
obstetrical emergency. Move the patient into the knee-chest position and try
to elevate the fetal head off the cord with your examining hand. Transport
the patient in this position to the delivery room for immediate delivery.
With fetal heads, it is easiest to
first find the sagital suture. Once that is located, the anterior fontanelle
is identified by four suture lines coming together. The anterior fontanelle
is diamond shaped, but the forces of labor may distort that landmark.
Next, identify the posterior
fontanelle at the junction of three suture lines. The soft, triangular
shaped depression may or may not be present because of compression of the
With breech presentations, the
midline is first identified, followed by the bony prominence of the fetal
The status of the fetal membranes
can be determined during an exam. Sometimes the free flow of clear or
meconium stained amniotic fluid makes it obvious that the bag of waters is
ruptured. In other cases, it may be prudent to perform a sterile speculum
exam to obtain a specimen from the upper vagina for further testing. Vaginal
secretions are normally mildly acidic. The presence of alkaline amniotic
fluid will turn the nitrazine paper bright blue. Other methods include
examining dried fluid for ferning.
Clinical pelvimetry may be used to
estimate the pelvic capacity for delivery. Digital evaluation allows the
examiner to categorize the pelvis as probably adequate, borderline, or small
for an average sized baby.
Measure the diagonal conjugate by
inserting two fingers into the vagina until they reach the sacral
promontory. The distance from the sacral promontory to the exterior portion
of the symphysis is the diagonal conjugate and should be greater than 11.5
Feel the ischial spines for their
relative prominence or flatness. Spinal prominence narrows the transverse
diameter of the pelvis and can make delivery more difficult.
Feel the pelvic sidewalls to
determine whether they are parallel, diverging or converging. Parallel or
diverging are fine, but converging is associated with outlet obstruction.
Fortunately, true outlet obstruction is rare.
Measure the distance between the
ischial tuberosities by pressing your closed fist against the perineum.
Greater than 8 centimeters is considered normal.