Variations in some of the body fluid hormone levels currently used for endocrine monitoring during the third trimester of pregnancy.

We have investigated the variability of four hormonal parameters used for the endocrine monitoring of the third trimester of pregnancy (E3, E4, HPL, SP1). We have observed no circadian rhythm of Estriol, Estetrol, HPL, and SP1. The within-a-day and the day-to-day variations are much greater for E4 than for E3 and for HPL than for SP1. The standard deviations were great for the steroids, especially for E4 and much less for the protein hormones, especially SP1. This implies that it is necessary to have serial assays of the steroids to have any confidence in the levels, while good monitoring could be guaranteed with a smaller number of assays for HPL, and SP1.