Obstetrics & Gynecology (OBGYN)

Syllabus Unit: Clinical Medicine & Surgery

Why it matters

Chapter overview

OBGYN spans the physiology of normal labour, the threshold-based recognition of high-risk pregnancy complications like pre-eclampsia and antepartum haemorrhage, the etiology and staging of gynaecological cancers, and the mechanism-based comparison of contraceptive methods — a unit where AIIMS PG rewards knowing the exact diagnostic cut-off or drug regimen as much as the underlying pathophysiology.

Postgraduate Medical Exam Syllabus Clinical Medicine & Surgery 50% weightage

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1Engagement & DescentFetal head enters and descends through the pelvic inlet

2FlexionHead flexes to present its smallest diameter

3Internal RotationHead rotates to align with the pelvic outlet

4Extension & ExpulsionHead extends under the symphysis and delivers

1Normal Pregnancy & Labour

Labour is divided into three defined stages, each with an expected time limit and progress plotted on the WHO partograph to catch delay early.

Learning Objectives

Define the three stages of labour and their normal duration in primigravida versus multigravida.
Plot and interpret a partograph, including the alert line and action line.
Describe the cardinal movements of normal vertex delivery, from engagement to expulsion.
Distinguish true labour pain from Braxton Hicks contractions.

Key Terms

PartographA WHO graphic tool plotting cervical dilatation against time during active labour; the 'alert line' (1cm/hour) and 'action line' (drawn 4 hours to its right) flag delayed progress.

Stage 1 of LabourFrom the onset of true labour to full cervical dilatation (10cm); subdivided into the latent phase and the active phase, where dilatation should proceed at ≥1cm/hour in a primigravida.

Cardinal MovementsEngagement, descent, flexion, internal rotation, extension, external rotation (restitution) and expulsion — the sequence the fetal head undergoes passing through the birth canal.

Braxton Hicks ContractionsIrregular, painless 'practice' uterine contractions that occur throughout pregnancy but, unlike true labour, do not produce progressive cervical change.

Normal labour is defined by fixed time-based stages and a fixed movement sequence for the fetal head — both are plotted or checked against expected norms, which is exactly what the partograph and the cardinal movements test.

The three stages of labour

Latent phase → Active phase (dilatation ≥1cm/hr) → Full dilatation (10cm) = end of Stage 1 → Delivery of baby = Stage 2 → Delivery of placenta = Stage 3

The partograph

Cervical dilatation is plotted against time once the active phase begins; the alert line represents the expected 1cm/hour progress, and the action line, 4 hours to its right, is the threshold at which prolonged or obstructed labour must be actively addressed.

Cardinal movements of labour

Engagement — the fetal head's widest diameter passes the pelvic inlet.
Descent and flexion — the head descends and flexes to present its smallest diameter.
Internal rotation — the head rotates to align with the pelvic outlet.
Extension and expulsion — the head extends under the pubic symphysis and delivers, followed by external rotation (restitution) and delivery of the shoulders.

Exam TipTrue labour pain is regular, increasing in frequency/intensity, and causes progressive cervical change — Braxton Hicks contractions are irregular and do not dilate the cervix.