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Normal and arrested labour
Labour progresses when there is enough power (contractions), a suitable passenger (the fetus and its position) and an open passage (the pelvis); arrest is diagnosed only after defined times in the active phase, and before a caesarean you ask which of the three has failed.
Why it matters in the exam
Labour questions test the newer definitions: the active phase starts at 6 cm of dilatation, and active-phase arrest is defined only at 6 cm or more with ruptured membranes and no change for 4 hours of adequate contractions or 6 hours with oxytocin. In the second stage, wait at least 3 hours of pushing in a nulliparous woman and 2 hours in a multiparous one. These definitions were meant to prevent unnecessary caesareans, and the distractors in questions are built on the older definitions.
Further topics: the Bishop score and cervical ripening before induction (8 or more — a favourable cervix), induction at 41 weeks and not after 42 weeks, the conditions for operative vaginal delivery (full dilatation, ruptured membranes, engaged head, known position, empty bladder), vaginal birth after caesarean (TOLAC) and shoulder dystocia. In shoulder dystocia the first step is the McRoberts position with suprapubic pressure, and never fundal pressure. The fetal complication that is asked about is Erb palsy (roots C5–C6).
Key points
- The active phase starts at 6 cm.
- Active-phase arrest: 4 hours with adequate contractions or 6 hours with oxytocin, without change.
- Second stage: 3 hours in a nulliparous woman, 2 hours in a multiparous one.
- Shoulder dystocia: McRoberts and suprapubic pressure; never fundal pressure.
- TOLAC after one caesarean with a low transverse incision; not after a classical incision.
Summary table
| Stage | Starts and ends | Arrest or prolongation | What to do |
|---|---|---|---|
| First stage, latent | From regular contractions to 6 cm | Prolongation is not a reason for caesarean | Rest, analgesia, patience |
| First stage, active | From 6 cm to full dilatation | No change for 4 hours with adequate contractions or 6 hours with oxytocin, membranes ruptured | Amniotomy and oxytocin; true arrest → caesarean |
| Second stage | From full dilatation to birth of the baby | 3 hours of pushing in a nulliparous woman, 2 hours in a multiparous one (longer with an epidural) | Operative vaginal delivery (vacuum or forceps) or caesarean |
| Third stage | From birth of the baby to delivery of the placenta | Placenta not delivered after 30 minutes | Manual removal of the placenta |
| Shoulder dystocia | Anterior shoulder impacted behind the pubic bone | Turtle sign: the head retracts against the perineum | McRoberts and suprapubic pressure → deliver the posterior arm → rotation (Rubin, Woods) |
| TOLAC | Trial of labour after one caesarean with a low transverse incision | Uterine rupture risk 0.5%–0.9% | Forbidden after a vertical (classical) incision or a previous rupture |
A free exam question
בן 65. עבר לאחרונה התקף של אבני כליה. מתלונן על כאבים בירך. בבדיקות הדם: Alkaline Phosphatase 140 u/L (normal 30-120), Uric Acid 7 mg% (normal 3.5-7.2), Calcium 11 mg% (normal 8.5-10.5). בצילום ירך: התגלו אזורים ליטיים ואזורים עם עליה בצפיפות העצם והרחבה של העצם הטרבקולארית. מיפוי עצם: מראה אזורים בעלי קליטה רבה. מהי האבחנה הסבירה ביותר? (the question as examined, in Hebrew)
- א. Multiple Myeloma
- ב. Paget's Disease
- ג. Osteomalacia
- ד. Prostate Cancer
Example question from the licensing exam (IMLE)
Induction of labor is offered to a 41+4 weeks pregnant woman. Which of the following is the main reason for this recommendation?
- A. Prevention of intrauterine growth restriction
- B. Prevention of oligohydramnios
- C. Prevention of perinatal death
- D. Prevention of post-partum hemorrhage
In the full version for subscribers
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Sources
- ACOG/SMFM Obstetric Care Consensus No. 1, 2014, reaffirmed — Safe Prevention of the Primary Cesarean Delivery
- ACOG Practice Bulletin No. 205, 2019 — Vaginal Birth After Cesarean Delivery
- ACOG Practice Bulletin No. 178, 2017 — Shoulder Dystocia
- Williams Obstetrics, 26th edition (2022) — Normal Labor; Abnormal Labor; Induction and Augmentation of Labor
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.