Primigravida with full term, complains of faintness on lying down and she feels well when she turns to side or sitting position. This is due to:
SUPINE HYPOTENSION SYNDROME (POSTURAL HYPOTENSION): During late pregnancy, the gravid uterus produces a compression effect on the inferior vena cava when the patient is in supine position. This, however, results in opening up of the collateral circulation by means of paraveebral and azygos veins. In some cases (10%), when the collateral circulation fails to open up, the venous return of the hea may be seriously cuailed. This results in production of hypotension,tachycardia and syncope. The normal blood pressure is quickly restored by turning the patient to lateral position. The augmentation of the venous return during uterine contraction prevents the manifestation from developing during labor. Reference: Dutta's Textbook of Obstetrics 7th edition page 53
Increased abdominal pressure
IVC compression
Increased intracranial pressure
After heavy lunch
General obstetrics