Utero‐Placental Blood Flow and the Effect of β2‐Adrenoceptor Stimulating Drugs

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Abstract
The immediate effect of a β2‐adrenoceptor stimulating drug, salbutamol, on utero‐placental blood flow in the last trimester of pregnancy was evaluated in 16 women without uterine contractions, using a method applying 113‐m Indium and a computer‐linked gamma camera. Serial scintigrams over the placental site showed a 15 per cent increase in activity during a short salbutamol infusion, denoting an augmented blood pool in the intervillous space. At the end of a 25–30 min salbutamol infusion, a mean prolongation of the rise time of the isotope accumulation curve by 100 per cent could be calculated. A utero‐placental blood flow index derived from the ratio of the maximum activity and the rise time of the accumulation curve above the placenta showed a decrease ranging from 18 to 50 per cent. It is conceivable that this initial decrease would disappear during continued infusion, as has been shown to occur in the pregnant sheep model.