Wolfe, Charles David Alexander; (1990) Corticotrophin releasing factor in pregnancy. Doctoral thesis (M.D), UCL (University College London).

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Abstract

Using a "two-site" imnunoradiometric assay Corticotrophin Releasing Factor (CRF) has been measured in maternal plasma and elevated levels observed in the third trimester of pregnancy. The dilution curve of this CRF paralleled the IRMA standard curve. This CRF-like material eluted on reverse phase high pressure liquid chromatography with a retention time identical to that of synthetic CRF and had equipotent bioactivity with the synthetic peptide. Third trimester maternal plasma contains a carrier substance for CRF with a molecular weight in the region of 40,000. The binding capacity of the carrier is not saturated but most of the CRF in late gestational plasma is bound. In a group of 72 pregnant women CRF levels rose from a median of 20 pg/ml at 28 weeks to 1320 pg/ml at 40 weeks and 1732 pg/ml during labour. There was a strong correlation (r=0.81,P < 0.001) between gestational age and CRF levels. The rate of rise of CRF (pg/ml) per week was associated with weight gain (r= 0.36, P < 0.05) but with no other obstetric variable. There was an association between umbilical cord and maternal plasma CRF levels (r= 0.54, P < 0.01). CRF levels were elevated after accidental antepartum haemorrhage at 28 weeks (P < 0.03). In twin pregnancies maternal CRF levels were significantly raised throughout the third trimester (28-32 weeks, P < 0.01; 34-36 weeks, P < 0.001). In cases of pregnancy induced hypertension (28 weeks, P < 0.001; 32-36 weeks, P < 0.001 and 38-40 weeks, P < 0.01), preterm labour and premature rupture of the membranes (28 weeks, P < 0.004; 30-32 weeks, P < 0.002 and 34-36 weeks, P <0.001), CRF levels were significantly raised. Maternal plasma CRF levels did not correlate with total cortisol levels and did not display diurnal variation. Short term variation in plasma CRF levels had a Coefficient of Variation (CV) of 5.3 ± 0.52 pg/ml and the effect of posture had a CV of 7.1 ± 0.52 pg/ml. During and between uterine contractions in labour the CV was 4.5 ± 1.4 pg/ml and postpartum the half life of CRF was estimated at 65 minutes.

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