Placental transport of low molecular weight heparin in the pregnant XXXX .

@entity28052 @entity1031 @entity742 @entity548
Standard heparin, an effective treatment for antepartum @entity1031 , is thought to be safe for the fetus since it does not cross the placenta. Recently, a number of low molecular weight heparins have been prepared which have been shown to produce less @entity548 than standard heparin for an equivalent antithrombotic effect in experimental animals. These observations suggest that the low molecular weight heparins may also provide superior antithrombotic therapy in antepartum @entity1031 . However, it is not known whether the low molecular weight heparins cross the placenta. To determine this, we examined the pharmacokinetics of 125I-labelled standard heparin and a low molecular weight heparin, and their anticoagulant effects in mother and fetus, using a pregnant @entity742 model. Catheters were inserted into maternal and fetal femoral arteries at 108-119 d gestation (term: 147 d). 1-3 days later the mothers were given a bolus i.v. injection of 5000 anti-Xa units of 125I-labelled standard heparin or low molecular weight heparin, @entity28052 . Nine serial blood samples were collected over 4 h from both mother and fetus for measurements of radioactivity, anti-Xa activity (chromogenic) and activated partial thromboplastin times. When therapeutic levels of standard and @entity28052 heparins were achieved in the mother, there was no detectable radioactivity or anticoagulant effect in the fetus. We conclude that standard heparin and the low molecular weight @entity28052 do not cross the placenta in the pregnant @entity742 .
