The course and conduct of normal labor and delivery Emilia Brzezińska Division of Perinatal Medicine
A definition of labor Progressive dilatation of the uterine cervix in association with repetitive uterine contractions. Spontaneous or induced Term or preterm
Important terms Lie- relationship between the long axis of the fetus and that of the mother (longitudinal, transverse or oblique). Presentation- the fetal part that lies closest to the pelvic inlet (cephalic - vertex, face; breech; shoulder). Attitude- relationship of the fetal parts to each other, usually head and trunk (flexion or extension of the neck).
Onset of labor • Regular uterine contractions - from at least 1/2 hr, frequency at least every 10 minutes • Bleeding • Rupture of membranes
Stages of the labor I - shortening and dilatation of the cervix II - delivery of the fetus III - delivery of the placenta with the umbilical cord and membranes IV - about two hours after delivery (inspection and surgical help)
Dilatation of the cervix • Nullipara: I - shortening II - dilatation of external os III - dilatation of internal os • Multipara: phases I, II and III occur together
Mechanisms of labor The special labor mechanisms is due to asymmetry of the shape of both the fetal head and maternal pelvis. Changes in the position of the fetal head are required for the average size fetus to accomplish passage through the birth canal. The rotations are accomplished by the propulsive force of uterine activity.
Important! • Pelvic planes and diameters of the pelvic inlet • Diameters of fetal skull • Leopold’s maneuvers (Data in each manual of obstetrics)
Examination • External (Leopold’s maneuvers) • Internal • cervix - length and dilatation • membranes - intact or not, color of the amniotic fluid • fetus - presentation, attitude, rotation • pelvis - size
engagement descent 1. flexion 2. internal rotation 3. extension 4. external rotation expulsion movements of the head Cardinal movements of labor
Engagement It is the descent of the largest transverse diameter of fetal head (BPD) to a level below the plane of the pelvic inlet. Then the head is engaged.
Flexion (I movement of the head)- placement of the fetal chin on the thorax Internal rotation (II movement)- rotation from the transverse position towards symphysis.
Extension - III movement Begins at the level of maternal vulva The fetal head is delivered by extension from the flexed to the extended position rotating around the symphysis pubis
External rotation - IV movement After delivery of the head the forces exerted on the head by the maternal pelvic musculature are relived and the fetus resumes its normal face-forward position. Its face begins to „look” at one of mother’s leg.
Expulsion Delivery of the shoulders - first the anterior one (under the symphysis pubis) and then the posterior one. The rest of the body is usually quickly delivered.
Assisted spontaneous delivery • Lateral episiotomy • Prevention of rapid delivery of the head • Delivery of the shoulders and body • Aspiration of the mucus from the fetal mouth, pharynx and nose • Cord clamping
Episiotomy • A lateral incision of perineum before delivery of the head • Why? • to enlarge the area of the outlet easier delivery of the head prevention of intraventricular hemorrhage • prevention of lacerations • prevention of late complications - relaxation of pelvic muscles and urine incontinence
Episiotomy • Prophylactic - nulliparas, some multiparas • Mandatory • in instrumental delivery, like forceps or vacuum extractor • in abnormal presentations, like breech • in preterm deliveries
Monitoring of fetal well-being Continuous fetal heart rate and contractions monitoring (CTG) - external or direct • baseline FHR • FHR variability • periodic FHR changes • decelerations (early, late, variable) • accelerations • sinusoidal FHR pattern Fetal capillary scalp blood sampling
Baseline FHR • between 110 and 150 bpm • < 100 - bradycardia (e.g. hypoxia) • > 160 - tachycardia (e.g. infection)
FHR variability • short-term, a beat-to-beat variability • normal ranges: 5 - 20 bpm from the basis • < 5 - loss of variability (silent) • > 25 - exaggerated variability
Deceleration • Decrease in FHR of at least 15 bpm lasting 15 s or longer • early - begins with the beginning of contraction, reaches its lowest point just with the peak of contraction • late - occurs in the late phase of contraction, its lowest point is after contraction • variable - no association with contractions
Deceleration • early - due to pressure of fetal head as it moves down the birth canal, reflex mediated by the vagus nerve • late - result of fetal hypoxia (uteroplacental insufficiency) • variable - effect of umbilical cord compression (cord around the neck, arm or between some part of the fetus and the uterine wall)
Acceleration • Increase in FHR of at least 15 bpm lasting 15 s or longer • associated with contractions or fetal movements • indicator that fetus is adequately oxygenated
Anesthesia for labor • Psychoprophylaxis - very important • teaching about physiology • breathing • stress control • husband participation • Narcotic drugs - attention: risk of respiratory depression in newborn • Subarachnoidal block