Unstable lie, transverse lie and shoulder presentation

1. Big picture

Unstable lie, transverse lie, and shoulder presentation are abnormal fetal lie/presentation problems that matter because they can rapidly become obstetric emergencies, especially after membrane rupture.

The core exam idea is:

A term fetus cannot usually deliver vaginally in transverse lie. The major danger is cord prolapse, obstructed labor, fetal hypoxia, and uterine rupture.

Think clinically in this order:

Abnormal lie suspected
        ↓
Confirm by ultrasound
        ↓
Look for cause: placenta previa, polyhydramnios, multiparity, uterine anomaly, pelvic mass, fetal anomaly, twins
        ↓
If term and persistent transverse lie → cesarean delivery
        ↓
If membranes rupture → exclude cord prolapse immediately
        ↓
If labor + transverse lie → emergency cesarean unless very specific exception, e.g. second twin with skilled internal podalic version

This topic is closely connected with malpresentation, cord prolapse, obstructed labor, cesarean section, and fetal distress.

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