VARIATIONS IN MATERNAL PLASMA LEVELS OF HUMAN PLACENTAL LACTOGEN (HPL) IN NORMAL PREGNANCY AND LABOUR

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Abstract
Summary: Plasma levels of human placental lactogen (HPL) in normal pregnancy from the 22nd week until delivery were measured with a rapid radioimmunoassay. The HPL concentration in plasma rose steadily up to the 37th week and thereafter gradually decreased until delivery. Individual women followed during the latter part of pregnancy showed a characteristic pattern with very small deviations from their original relative level within the normal range.Significant fluctuations in HPL levels were noted during a 24‐hour period of sampling and during shorter periods. No systematic circadian variation was observed. The variations showed no clear relation to sleep, meals or light exercise. During spontaneous and induced labour significant fluctuations in HPL concentrations occurred but these were of the same magnitude as those during the latter part of normal pregnancy; no correlation between HPL levels and uterine contraction and relaxation was found.Strenuous physical exercise during the last month of pregnancy sufficient to affect the fetal heart rate did not influence the HPL levels.

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