Major determinent of oxygen and nutrient transport to the fetus 

Direct correlation between UBF and fetal PO2

Increases with pregnancy 50-100 ml/min --> 700-900 ml/min

UBF= uterine arterial- uterine venous pressure

uterine vascular resistance 

PGI2 

ANP

Protein kinase C

General reduce sensitivity to vasoconstrictors

Uterine artery behaves as a neraly maximally dilated vessel 

Supine Position

Hemorrhage/ hypovolemia

Drug-induced hypotension

Hypotension during sympathetic blockade 

Vena Caval compression

Uterine contractions 

Drug- induced hypertonus 

Skeletal Muscle Hypertonus 

Endogenous Vasoconstrictors- catecholamines, vasopressin

Exogenous Vasoconstrictor- epinephrine, vasopressors, LA 

Acute stress cause 25% increase in plasma NE and 50% decrease in UBF

Increase in plasma Epi and increase in incidence of abnormal FHR patterns 

Increase UBF by decrease circulating catecholamines and preventing periods of hyperventilation during painful contraction 

Absence of hypotension, epidural anesthesia does not alter UBF 

Hypotension decreses UBF by decreasing perfusion pressure & stimulating endogenous vasoconstrictors 

More effective than a-agonists in restoring UBF

More likely to increase BP by increasing CO with less direct vasoconstriction 

May protect uterine perfusion by stimulating release of nitric oxide in uterine blood vessels 

Fetus unaffected by ephedrine 

HR < 100 

Fetal acidosis less with PE or combo than E

N/V least with PE

Increases maternal preload and CO 

Maternal bradycardia more likely with PE than with E

HR > 100 use PE

1-2 mg/kg 

Can increase uterine tone, causing a decrease in UBF

Clinical dose < 0.5 MAC have little or no effect on UBF

N2O has no effect on UBF 

Positive pressure ventilation causes decreased UBF

Adding CO2 did not improve UBF

Unintentional injection of 25 mg of bupiv has been associated with transient uterine hypertonus and fetal bradycardia

Bupiv more potent than lido or 2-CP 

LA constrict arteries directly and inhibit endothelium mediated vasodilation 

Does not affect uterine blood flow

Prolonged infusion can cause B-blockade and hypoxemia 

Produces less B-Blockade 

Does not decrease uterine blood flow 

Either improves or does not decrease intervillous blood flow when used to decrease BP in hypertensive women 

Prefered vasodilator for the initial treatment of severe HTN 

Rarely used in pregnancy

Verapamil & Nifedipine may decrease uteroplacental blood flow

May cause uterine atony after delivery 

Prostaglandic E-2

(Cervidil)

Given as a gel by OB

Uterine stimulant 

Used to augment labor contractions

Used to promote uterine contractions post partum 

Can cause hypotension if given rapidly-not given bolus form 

Used to promote uterine contraction post partum 

Bronchospasm in severe forms resulting in hypoxemia 

HTN

Nausea and Vomiting 

Do not give to asthmatics 

Used to promote uterine contraction post partum

Contraindicated after a vasopressor such as ephedrine has been given

Contraindicated in the presence of hypertension 

Beta-Agonists

Mg

Indomethacin, Motin

ETOH

NTG

Potent inhalation agents