Prolonged or Arrested Active Phase
A 20-year-old primigravida at 39 weeks’ gestation has progressed in labor to 8 cm of cervical dilation but has not changed for 3 h. Her vital signs are stable. EFM tracing is reassuring regarding fetal status.
Diagnosis. Cervical dilation is>4 cm, or the acceleration phase of dilation has been reached. Prolongation is diagnosed if cervical dilation is <1.2 cm/h in a primipara or <1.5 cm/h in amultipara. Arrest is diagnosed if cervical dilation has not changed for >2 h.
Causes. Active-phase abnormalities may be caused by either abnormalities of the passenger (excessive fetal size or abnormal fetal orientation in the uterus), abnormalities of the pelvis (bony pelvis size), or abnormalities of powers (dysfunctional or inadequate uterine contractions).
Management. This is directed at assessment of uterine contraction quality. Contractions shouldoccur every 2–3 min, last 45–60 s with 50 mm Hg intensity. If contractions are hypotonic, IV oxytocin is administered. If contractions are hypertonic, give morphine sedation. If contrac-tions are adequate, proceed to emergency cesarean section.
OB Triad
Prolonged Latent Phase
• Pregnant with regular uterine contractions
• Cervix dilated 2 cm
• No cervical change in 14 h
OB Triad
Prolonged Active Phase
• Pregnant with regular uterine contractions
• Cervix dilated 8 cm
• 2-cm change in 4 h
OB Triad
Active Phase Arrest
• Pregnant with regular uterine contractions
• Cervix dilated 8 cm
• No cervical change in 3 h
Prolonged Second Stage
A 20-year-old primigravida at 39 weeks’ gestation has progressed in labor to 10 cm of cervical dilation and has been pushing for the past 3 h without descent of the fetal head beyond +2 station. Her vital signs are stable. EFM tracing is reassuring regarding fetal status.
Diagnosis. Failure to deliver the baby in 2 hours (primipara) or 1 hour (multipara). With epi-dural analgesia add additional 1 hour.
OB Triad
Second-Stage Arrest
• Pregnant with regular uterine contractions
• 10 cm dilation at +1 station
• No descent change in 3 h
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USMLE Step 2 l Obstetrics
Cause. Same as active-phase abnormalities: passenger, pelvis, or powers.
Management. Involves assessment of uterine contractions and maternal pushing efforts. UseIV oxytocin or enhanced coaching as needed. If they are both adequate, assess whether the fetal head is engaged. If the head is not engaged, proceed to emergency cesarean. If the head is engaged, consider a trial of either obstetric forceps or a vacuum extractor delivery.
Prolonged Third Stage
A 20-year-old primigravida at 39 weeks’ gestation underwent a spontaneous vaginal delivery 40 min ago of a healthy 3,500-g daughter. However, the placenta has still not delivered. Her vital signs are stable.
Diagnosis. Failure to deliver the placenta within 30 minutes.
OB Triad
Prolapsed Umbilical Cord
• Pregnant with regular uterine contractions
• Amniotomy at –2 station
• Severe variable decelerations
Cause. May be inadequate uterine contractions. If the placenta does not separate, in spite of IVoxytocin stimulation of myometrium contractions, think of abnormal placental implantation (e.g., placenta accreta, placenta increta, and placenta percreta).
Management. May require manual placental removal or rarely even hysterectomy.
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