One of the most problematic issues of assisted reproduction is the high incidence of multiple pregnancies, resulting from the transfer of more than one embryo. Particularly at risk are young women who have good quality embryos. The only strategy to reduce the incidence of multiple pregnancies, including twin pregnancies, after assisted reproduction is single embryo transfer (SET). In 1997, the present authors therefore introduced elective SET (eSET) in this particular target group. The proportion of eSET increased from 1.5 (1997-1998) to 17.5% (1999-2002) of all transfers. In 2002, 20% of all transfers were SET. Comparing these two periods, an overall pregnancy rate of 35 and 34% per transfer, respectively, was obtained, while the overall twinning rate dropped from 30 to 21%. The twinning rate dropped to 14% in 2002, and in the eSET group there was only one monozygotic twin. These results demonstrate that a decline in the twinning rate is feasible without a drop in overall pregnancy rates. Comparing eSET with elective double embryo transfer (eDET), it was found that ongoing pregnancy and implantation rates were the same in both groups, but the proportion of twins was clearly different. It was further observed that the mean birthweight of singleton children born after eSET was significantly higher than that after DET. This could reflect a better developmental or implantation potential of these embryos, but this finding remains to be confirmed.
A total of 31 clomiphene citrate/human menopausal gonadotrophin (HMG)/human chorionic gonadotrophin (HCG)-stimulated cycles in 28 patients were investigated to determine the fate of each of the matured follicles. A standard stimulation regimen was adhered to, and ultrasound as well as hormonal monitoring was performed. All follicles were measured by vaginal ultrasound at -12, +35 and +45 h relative to HCG administration and at 7 days after HCG administration. Of the 220 follicles, 107 (48.6%) ruptured. The number of ruptured follicles per cycle was correlated with the mid-luteal progesterone concentration (r = 0.63, P = 0.0005). The probability of follicular rupture was related to follicular diameter at 12 h before HCG administration; 6% of follicles < 12 mm in diameter ruptured compared with 87% of follicles 18-19 mm. A complete luteinized unruptured follicle (LUF) syndrome was observed in six cycles (20%). In these cycles, follicular growth and oestradiol, progesterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH) concentrations at 12 h before HCG administration were similar to those in cycles with follicular rupture. However, mid-luteal progesterone concentrations were lower in complete LUF cycles (46.97 +/- 8.95 nmol/l versus 108.74 +/- 12.27 nmol/l; P = 0.02). These data demonstrate that in stimulated cycles many follicles, usually the smaller ones, fail to rupture, even after HCG administration. Complete LUF syndrome, despite a strong exogenous ovulatory signal, and the absence of any difference in peri-ovulatory hormonal parameters, indicates that the defect causing LUF resides in the follicle itself and/or hormonal changes during the follicular phase.
Propofol (2,6-diisopropylphenol, Diprivan, ICI-Pharmaceuticals, Manchester, UK) is widely used either as an adjunct in general anaesthesia or as sole anaesthetic agent by the continuous intravenous route and intermittent bolus injections for minor surgical interventions. For several years, we have been using this kind of anaesthesia in transvaginal oocyte retrieval for in-vitro fertilization (IVF), allowing a completely painless puncture on an out-patient basis. From in-vitro studies on mouse oocytes, it appeared that propofol could be deleterious for fertilization in a dose- and time-dependent manner. We therefore investigated the concentrations of propofol in follicular fluid during oocyte retrieval in women. We measured propofol levels in serum and follicular fluid of nine patients at fixed intervals during ultrasound guided oocyte retrieval. Serum levels fluctuated randomly, due to interference from top-off doses of propofol. In follicular fluid, however, we found a steady increase of propofol levels, which was proportional to the total dose of propofol administered. These data indicate that propofol accumulates in follicular fluid. Although it seems unlikely that propofol as used in the present protocol exerts a clinically significant unfavourable effect on IVF, we suggest that the oocyte retrieval procedure should be kept as short as possible, in order to limit the accumulation of the anaesthetic in follicular fluid.
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