Normal Labor and Delivery Barbara M. O’Brien, M.D. Maternal Fetal Medicine and Genetics 1

Normal Labor and Delivery Definition of labor: uterine contractions that cause cervical change term pregnancy: 37-42 weeks preterm: <37 weeks Postdates pregnancy: >42 weeks 21

Stages of labor First Stage-- stage of cervical effacement and dilation Begins when uterine contractions of sufficient frequency, intensity, and duration are attained to bring about effacement and progressive dilation of the cervix Ends when the cervix s fully dilated (10 cm) to allow passage of the fetal head 22

First Stage of Labor

Stages of labor Second stage of labor-- stage of expulsion of the fetus begins when dilatation of the cervix is complete and ends with delivery of the fetus 23

Second Stage of Labor

Stages of labor Third stage of labor-- stage of separation of separation and expulsion of placenta begins immediately after delivery of the fetus and ends with delivery of the placenta and fetal membranes 24

Third Stage of Labor

Divisions of First Stage of Labor Divides 1st stage into latent and active phase: latent phase: onset of labor is defined according to Friedman as the point at which the mother perceives regular contractions regular ctx take place along with cervical softening and effacement prolonged latent phase: defined as greater than 20 hours in a nullipara and greater than 14 hours in a parous woman

Divisions of First Stage of Labor Active phase: cervical dilation rate of 1.2 cm/hr for nulliparas and 1.5 cm/hr for parous women These rates of cervical dilation do not start at a specific dilatation cervical dilation of 3 or 4 cm or more, in the presence of uterine contractions can be taken to reliably represent the threshold for active labor nullipara on average dilate 1.2 cm/hour and multips on average dilate 1.5 cm/hour (minimum)

Mechanisms of Normal Labor Fetal orientation is described with respect to fetal lie, presentation, attitude, and position These can be established clinically by abdominal palpation, vaginal exam, or by U/S Fetal lie: the lie is the relation of the long axis of the fetus to the mother and is either longitudinal or transverse

Mechanisms of Normal Labor Fetal presentation: the presenting part is the portion of the body of the fetus that is either foremost within the birth canal or is in closest proximity to it. In longitudinal lies, the presenting part is the fetal head or breech In transverse lies, the presenting part is the shoulder

Mechanisms of Normal Labor Cephalic presentation: Classified according to the relation of the head to the body of the fetus Breech presentation: frank breech: when thighs are flexed and legs are extended over the anterior surfaces of the body complete breech:if thighs are flexed on abdomen and legs upon thighs incomplete or footling: if one or both feet, or one or both knees, are lowermost

Types of Breech Presentations

Mechanisms of Normal Labor Frequency of Various Positions at term: Vertex: 96% Breech 3.5% Face: 0.3% Shoulder: 0.4% Diagnosis of Fetal Presentation and Position: Abdominal Palpation/Leopold Maneuvers

Mechanisms of Normal Labor Cardinal Movements of Labor: Engagement: BPD passes through the pelvis inlet Descent Flexion: chin is brought into contact with fetal thorax Internal Rotation: turning of the head such that the occiput moves towards the pubic symphysis or posteriorly extension: of the head (or breech) so it can pass External rotation: head undergoes restitution expulsion: delivery of the anterior and posterior shoulders

Identification of Labor Uterine contraction that cause cervical change Vaginal Exam: note dilation, effacement, consistency, station Ruptured membranes? Fern, pool, nitrazine test sterile speculum infrequent vaginal exams if SROM

Maternal Monitoring and Management during Labor Maternal Vital Signs every 4 hours if temperature: chorioamnionitis: need to treat with antibiotics that will cover gram negative and anaerobes (ampicillin and gentamicin Group B strep is a big offender and we have moved to universal screening Oral Intake: food should be withheld during active labor Analgesia

Spontaneous Delivery Spontaneous Delivery Delivery of the head Episiotomy vs. no episiotomy clearing the nasopharynx check for a nuchal cord Delivery of the shoulders clamping the cord Watchful waiting for the placenta unless there is unusual bleeding give oxytocin Do any vaginal repair as needed