Endocrinological and ultrasonographic variations after immature oocyte retrieval in a natural cycle

BACKGROUND: In-vitro oocyte maturation is an appealing alternative in repro ductive medicine but the results obtained are still poor. The aim of our pr ospective and observational investigation was to study the hormonal modific ations that immature follicular aspiration might induce in a natural cycle as well as the implications that these alterations may have in the endometr ium. METHODS: Eleven patients (13 cycles) were included in our in-vitro ooc yte maturation programme. Ovaries were scanned with transvaginal probes eve ry day and follicular aspiration was performed when a follicle of 9 mm was visualized. Blood was also drawn for hormonal analysis. Endometrial thickne ss was recorded every day after oocyte retrieval. Two endometrial biopsies were taken on days 6 and 8 after oocyte retrieval. RESULTS: We observed a s ignificant drop in serum oestradiol concentrations after immature oocyte re trieval previous to follicle dominance. Immediately after, rises in both FS H and LH were detected. Also, a new dominant follicle started to grow 3-4 d ays later. Steroid hormones secreted by this newly recruited follicle were significantly lower than in controls, inducing inadequate endometrial thick ness. CONCLUSIONS: These studies show that exogenous hormonal administratio n might be necessary to achieve a correct endometrial growth when in-vitro oocyte maturation is employed in IVF.