Significance of oestradiol values in IVF–ET under a combined GnRH analogue—desensitization and simultaneous gonadotrophin stimulation for the outcome of pregnancies

: The present study was undertaken to determine the relationship between the actual value of oestradiol (E2) levels at the time of human chorionic gonadotrophin (HCG) administration and 36 h later at follicular puncture in in-vitro fertilization and embryo replacement (IVF-ET) patients and the resulting pregnancy rates. Between January and May 1988, 94 patients underwent follicular recruitment with various types of human menopausal gonadotrophin (HMG), follicle stimulating hormone (FSH) and HCG stimulation protocols. E2 and luteinizing hormone (LH) measurements were taken daily beginning on day 2 of the cycle. After an initial sonographic scan at the beginning of the treatment, vaginal sonographic follicular studies were performed based on the associated oestradiol levels from approximately day 8 of the cycle on. Four findings resulted: (i) When follicles reached a diameter of greater than 1.5 cm, the aspirated oocytes were at all stages of maturity. One can rely on follicular diameters alone if the patients' previous cycles and their E2 responses are known. (ii) A minimum plasma level of greater than 800 pg of E2 on the day of administration of HCG is predictive of a favourable pregnancy success rate per embryo transfer. Oestradiol levels do not, however, directly correlate with oocyte maturity and embryonic growth. (iii) The pregnancy rates in the low responding group when compared to the medium and high responding groups were statistically significantly lower despite replacement of an equivalent number of oocytes and cleaving embryos. (iv) We hypothesize that the responsiveness of the endometrium depends on adequate stimulation with oestradiol which it does not receive in the low responders.