Summary. Maternal plasma levels of cortiocotrophin‐releasing factor (CRF) have been measured in abnormal pregnancy states to assess their potential as biochemical markers for at‐risk pregnancies. CRF levels were not significantly altered in patients with hydatidiform mole, polyhydramnios or diabetes. CRF levels were elevated in pregnancies complicated by accidental antepartum haemorrhage at 28 weeks (P<0·03) but not for the rest of the third trimester. In twin pregnancies CRF levels were significantly raised throughout the third trimester (28–32 weeks, P<0·01; 34–36 weeks, P<0·001). In patients with 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 and in some patients levels were elevated 11 weeks before the onset of signs or symptoms. These observations raise the possibility that maternal CRF measurement may be of use as a predictive indicator of certain at‐risk pregnancies.

Summary. Corticotrophin‐releasing factor (CRF) was measured directly in maternal plasma using an immunoradiometric assay (IRMA). In the first and second trimester CRF levels were within the non‐pregnant range (mean 15 pg/ml). A total of 72 women was followed sequentially from 28 weeks until delivery and 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 (rs= 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 (rs= 0·36, P<0·05) but with no other obstetric variable. There was an association between umbilical cord and maternal plasma CRF levels (rs= 0·54, P<0·01).

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Context: Debate persists around the success rates of cleavage stage versus blastocyst transfers in fresh cycles. Freeze all and embryo pooling protocols have made vitrification and thaw cycles indispensable, introducing another angle to the decision for the best stage to cryopreserve embryos. Aims: To compare the pregnancy rates of embryos vitrified and transferred post-thaw on day 5 (FOD5) against that of embryos vitrified on day 3 and transferred post-thaw after culture as day 4 morulas or day 5 blastocysts (FOD3). Settings and Design: Retrospective study in a private clinic. Methods and Material: A total of 163 freeze-thaw transfer cycles in two groups. One group involved 76 cycles whose embryos were vitrified on day 3 (FOD3) and transferred either after culture to day 4 morulas or day 5 blastocysts. Another group was of 86 cycles in which blastocysts were cryopreserved on day 5 (FOD5) and transferred after a 2-hour incubation period post-thaw. Statistical analysis used: [i] Odds ratio of success for dichotomous outcomes [ii] the Chi-squared method. Results: 37 of the 76 FOD3 cycles (48.68%) and 41 of the 86 FOD5 cycles (47.67%) had a positive outcome. Conclusions: No statistical difference in pregnancy rates between embryos cryopreserved at cleavage stage on day 3 followed by a minimum of 1 day of culture post-thaw versus those cryopreserved and transferred at the blastocyst stage.

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