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Biochemical monitoring was undertaken in 22 treatment cycles for women with normal ovarian function who underwent pituitary suppression with buserelin and administration of exogenous oestradiol (E2) and progesterone (P) for cryopreserved embryo transfer (ET). Eighteen transfers of 1-4 thawed embryos, on the third day of exposure to progesterone, resulted in five clinical pregnancies (27.8%) and one biochemical pregnancy. There was no difference between pregnant and non-pregnant patients in the number and quality of embryos transferred, age, weight or infertility diagnosis. Serum E2 level from days 10-17 (the late proliferative phase) of the therapy cycle were significantly higher in the pregnant group compared with the non-pregnant group (P less than 0.05--P less than 0.005). There were no significant differences in P levels between the two groups from the onset of progesterone administration to the end of the cycle. However, as might be expected, the mean E2/P molar ratio in the pregnant group was significantly higher at the time of ET (P less than 0.02). It is concluded that biochemical monitoring during the embryo replacement cycle is necessary to tailor drug dosages for individual requirements to achieve adequate E2 levels before ET. Alternative routes of oestradiol administration need to be considered in patients with poor E2 profiles.

The circulating levels of placental protein 14 (PP14) and progesterone were measured in three pregnancies resulting from the transfer of cryopreserved embryos. Two of these women had suppressed ovarian activity as a result of pituitary down-regulation with the luteinizing hormone-releasing hormone agonist (buserelin) prior to treatment with exogenous oestradiol and progesterone. After 14 days of oral oestradiol treatment and if the endometrial thickness was greater than 7 mm, progesterone was given intramuscularly for a further 14 days with embryo transfer on the third day of this treatment. On confirmation of pregnancy by human chorionic gonadotrophin analysis, progesterone administration was altered to transvaginal pessaries for maintenance of adequate progesterone levels and endometrial support. In the two women with ovarian suppression, PP14 levels remained below the 2.5th centile of the normal range for pregnancy. In the third pregnancy, embryo transfer was performed 3 days after a spontaneous luteinizing hormone surge in a normal menstrual cycle. In this pregnancy, PP14 levels were within the normal range. Ultrasonic examination confirmed three normal ongoing singleton pregnancies. These results suggest that the majority of PP14 production in normal pregnancy is under ovarian or anterior pituitary control and that the influence of progesterone is of a secondary nature.