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OG13.1-8 | Normal Labour — Practice Quiz
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The obstetric conjugate of the pelvic inlet is the shortest antero-posterior diameter through which the fetal head must pass. Which of the following best describes how the obstetric conjugate is measured?
Correct. The obstetric conjugate extends from the sacral promontory to the lower inner border (most prominent part) of the pubic symphysis, averaging ~11 cm. This is the critical diameter limiting the fetal head at the inlet.
The obstetric conjugate (~11 cm) is the clinically critical diameter at the inlet; it cannot be measured directly — it is estimated from the diagonal conjugate (~12.5 cm) by subtracting 1.5 cm.
The obstetric conjugate is measured from the sacral promontory to the LOWER inner border of the pubic symphysis (not upper). The diagonal conjugate goes to the lower border of the symphysis and can be measured clinically (~12.5 cm); subtract 1.5 cm to estimate the obstetric conjugate.
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In Caldwell-Moloy classification, the gynaecoid pelvis is favourable for vaginal delivery primarily because of which of the following features?
Correct. The gynaecoid pelvis has a round/slightly oval inlet, well-curved sacrum, wide interspinous diameter (~10.5 cm), and a wide subpubic arch — all of which permit easy engagement and descent of the fetal head.
Gynaecoid (50% of women): round inlet, wide mid-pelvis, wide subpubic arch — most favourable. Android: heart-shaped, android pelvis is the most unfavourable for vaginal birth.
Option A describes the platypelloid pelvis (flat, wide transverse). Option C describes the android pelvis (heart-shaped, narrow arch — worst for delivery). Option D describes the anthropoid pelvis (oval antero-posteriorly, narrow transversely). Only the gynaecoid type has features uniformly favourable for vaginal birth.
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A primigravida in active labour reaches full cervical dilatation. The fetal head is in the right occiput transverse (ROT) position. Which cardinal movement MUST occur next for the head to pass through the mid-pelvis?
Correct. Internal rotation rotates the occiput from the transverse position toward the anterior midline (to OA). This is essential because the narrowest pelvic diameter (interspinous ~10.5 cm) is transverse at mid-pelvis; the fetal head must align its longest dimension (occipito-frontal) with the larger antero-posterior diameter of the outlet.
Cardinal movements in OA: engagement → descent → flexion → internal rotation → extension → restitution → external rotation/expulsion. Internal rotation brings the occiput to lie under the pubic arch.
Engagement (head entering the inlet) and flexion (reducing presenting diameter) occur earlier. Extension happens after the head reaches the perineum. Once the head is fully dilated and in the transverse position at mid-pelvis, internal rotation is the required next movement to align the occiput anteriorly.
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On the WHO partograph, the alert line and action line are plotted starting from 4 cm cervical dilatation. What is the time interval between these two lines, and what is the rate of progress each line represents?
Correct. The alert line represents 1 cm/hour active-phase progress starting at 4 cm. The action line is drawn 2 hours to the right of the alert line. If progress crosses the action line, intervention is required.
Alert line: 1 cm/h from 4 cm. Action line: 2 hours to the right. Progress left of the alert line is normal; crossing the action line mandates intervention.
The alert line is set at 1 cm/hour (the minimum acceptable rate of active-phase cervical dilatation). The action line is placed exactly 2 hours to the right of the alert line — this gives a 2-hour window to reassess and intervene before mandatory action.
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A woman delivers the baby and 5 minutes later shows signs of placental separation: a gush of blood, lengthening of the umbilical cord, and uterine fundus rising and becoming globular. What is the most appropriate next step in active management of the third stage?
Correct. Active management of the third stage (AMTSL) consists of: (1) uterotonic (oxytocin 10 IU IM/IV within 1 minute of delivery), (2) controlled cord traction with uterine counter-pressure (Brandt-Andrews), and (3) uterine massage. Signs of separation have appeared — proceed with controlled cord traction.
AMTSL: oxytocin 10 IU IM (within 1 min) → controlled cord traction with counter-pressure → uterine massage. Signs of placental separation: gush of blood, cord lengthening, uterus globular and rising.
Waiting 60 minutes applies to expectant (physiological) management. Manual exploration is reserved for retained placenta after 30 minutes or suspected incomplete. Ergometrine alone is not first-line (misoprostol or oxytocin is preferred; ergometrine is contraindicated in hypertension). The correct AMTSL sequence is uterotonic → controlled cord traction → uterine massage.
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A 26-year-old G2P1 at 30 weeks gestation presents with painless watery vaginal discharge for 2 hours. Pooling is visible on speculum examination and the Nitrazine test is positive. Contractions are absent. What is the most appropriate initial management?
Correct. This is preterm premature rupture of membranes (PPROM) at 30 weeks. Management is expectant: admit, antenatal corticosteroids (betamethasone 12 mg IM × 2 doses 24 hours apart) to accelerate fetal lung maturity, antibiotics (erythromycin/amoxicillin to prolong latency), and tocolysis if contractions begin. Delivery is deferred pending corticosteroid effect and fetal status.
PPROM <34 weeks: expectant management — corticosteroids, antibiotics (latency), tocolysis if contracting, GBS prophylaxis. At ≥34 weeks, delivery is generally recommended. Infection surveillance is mandatory throughout.
Immediate induction risks prematurity without steroid cover. Emergency LSCS is not indicated without fetal compromise or cord prolapse. Cerclage is contraindicated once membranes have ruptured. Expectant management with steroids + antibiotics is the evidence-based approach at 30 weeks.
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Which of the following tocolytic agents is considered first-line for preterm labour between 28–34 weeks because of its effectiveness, oral route, and relatively safe side-effect profile?
Correct. Nifedipine (calcium channel blocker) is the current preferred first-line tocolytic in many Indian centres — it is oral, inexpensive, effective at delaying delivery by 48 hours (the steroid window), and has fewer maternal side effects than ritodrine IV.
Tocolytics aim to delay delivery by 48 hours to allow corticosteroids to act. Nifedipine (oral) is first-line in most guidelines; magnesium sulfate is used for neuroprotection <32 weeks (not primarily as tocolytic).
Ritodrine IV is associated with significant maternal cardiovascular side effects. Indomethacin is used <32 weeks but carries risks of premature ductus closure and oligohydramnios with prolonged use. Atosiban is effective but expensive and parenteral. Nifedipine (oral) is the most widely recommended first-line agent.
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Before performing an artificial rupture of membranes (ARM), which of the following conditions MUST be confirmed to minimise the risk of cord prolapse?
Correct. Cord prolapse is the major immediate risk of ARM. It is prevented by ensuring the presenting part is well-engaged and tightly applied to the lower uterine segment/cervix before rupturing membranes. A free-floating head leaves space for cord to slip past when amniotic fluid releases suddenly.
ARM contraindications include: unengaged/high presenting part, cord presentation, placenta praevia, transverse lie, active genital herpes. Always confirm fetal heart rate immediately after ARM to detect cord prolapse.
While cervical dilatation and FHR stability are relevant to overall labour management, the critical safety condition for ARM specifically is that the presenting part is engaged and well-applied. An unengaged or high presenting part is a contraindication to ARM due to cord prolapse risk.
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A primigravida in active labour has intact membranes, 6 cm dilatation, and regular contractions. You decide to plot her on the partograph. At which point does plotting BEGIN on the standard WHO partograph?
Correct. The WHO partograph cervicograph starts at 4 cm, plotted on the alert line. The first cervical dilatation recorded on admission is placed directly on the alert line regardless of when in labour the patient was examined.
The standard WHO partograph: plot starts at 4 cm on the alert line. Alert line rises at 1 cm/hour; action line is 2 hours to the right. All assessments are plotted sequentially from this starting point.
The first recording goes directly ON the alert line at whatever dilatation ≥4 cm the patient is on admission. Option D (6 cm) relates to the WHO 2018 definition of active phase onset but the standard partograph still begins plotting at 4 cm on the alert line.
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A labouring woman asks to have her mother present during delivery. The senior nurse refuses, saying 'it is against ward policy.' According to the White Ribbon Alliance Respectful Maternity Care Charter, which right of the woman is being violated?
Correct. The WRA RMC Charter includes the right to companionship of choice during labour and childbirth. Denying a support person without clinical justification violates this specific right. Evidence also shows that continuous labour support shortens labour and improves outcomes.
WRA RMC Charter — 7 rights: (1) freedom from discrimination, (2) freedom from harm/ill-treatment, (3) information/consent/choices, (4) dignity and respect, (5) equality/freedom from discrimination, (6) companionship, (7) continuity of care. Denial of a birth companion violates right 6.
The right to freedom from harm (right 2) covers physical/emotional abuse. The right to information and consent (right 3) covers clinical decisions. Confidentiality (right 5) covers sharing of information. Companionship is explicitly one of the seven rights under the WRA charter.
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