The objective of this study was to determine the mechanism for higher pregnancy rates in oocyte recipients by comparing the pregnancy rates following fresh and frozen embryo transfers in a shared oocyte programme. A prospective study was carried out of 135 matched pairs of donors and recipients who equally share the donors' pool of oocytes. Recipients were subclassified by ovarian function: 69 were in ovarian failure and 66 retained ovarian function. A total of 474 standard in-vitro fertilization cycles using the same ovarian stimulation protocol as the donors were also evaluated. The main outcome measures were the clinical pregnancy and implantation rates for donors and recipients following fresh and frozen embryo transfers. The clinical pregnancy rates per transfer for fresh embryo transfers were 17.5% for donors, 20.4% for recipients with ovarian function and 46.3% for recipients in ovarian failure (P < 0.05). The pregnancy rates for frozen embryo transfers were 15.3% for donors, 17.2% for recipients with ovarian function and 23.8% for recipients in ovarian failure (not significantly different). The implantation rates for fresh transfers were 7.5% for donors, 8.6% for recipients with ovarian function and 15.6% for recipients in ovarian failure (P < 0.05); for frozen cycles, the implantation rates were 5.1, 5.2 and 7.1% respectively (not significantly different). When classified by age and ovarian function, the clinical pregnancy rates per transfer for recipients with ovarian function were 14.0% for those aged > or = 40 and 22.2% for those aged < 40 years. For recipients in ovarian failure, the pregnancy rates were 33.3% for the older group of women and 39.4% for the younger group. A logistic regression analysis found that ovarian function was the only factor to have an independent effect on outcome. The demonstration of higher pregnancy and implantation rates in recipients versus donors following fresh embryo transfer, despite the use of a common pool of oocytes, strongly suggests that the well-known higher fecundity found in recipients is not predominantly related to the use of better quality oocytes. The demonstration of an implantation rate twice as high following fresh versus frozen embryo transfer in recipients with ovarian failure suggests that the frozen embryo is not as hardy as the fresh embryo. Thus, the fact that both the pregnancy and implantation rates in donors were the same with fresh versus frozen embryo transfer suggests that the ovarian stimulation regimen has a negative effect on outcome. However, the clear demonstration of higher pregnancy rates in recipients with ovarian failure compared with those with ovarian function suggests that, in addition, these higher rates may be linked to a superior uterine environment in patients with ovarian failure. Alternatively, the use of gonadotrophin-releasing hormone agonists may have a negative effect on implantation in patients with ovarian function.

Progesterone induced blocking factor seen in pregnancy lymphocytes soon afer implantation. AJRI 1996; 35:277-280 0 Munksgaard, Copenhagen PROBLEM: The immunomodulatory effect of progesterone (P) in pregnancy manifested via a protein named the P-induced blocking factor (PIBF) was previously reported. The goal of this study was to measure and compare the PIBF expression on lymphocytes between pregnant and non-pregnant women especially in early pregnancy. METHODS: PIBF expression was determined by immunocytochemistry using a PIBF-specific polyclonal antibody. Levels were assessed during the mid-cycle, luteal phase, and first trimester of pregnancy. RESULTS: PIBF expression was found in 24.9% of mid-cycle sera, 49% of luteal phase sera of women who failed to conceive, and 75% of luted phase sera of women who conceived. CONCLUSIONS: These data indicate that the percentage of PIBF expressing lymphocytes increases as a result of pregnancy and that the stimulus for PIBF induction occurs soon after implantation. These data support the concept that PIBF may play an important role in early implantation possibly by inhibiting the destructive function of natural killer lymphocytes.

This study examines two descriptive parameters of embryo morphology to determine if either parameter correlates with subsequent pregnancy rates (PRs). The two parameters were the evenness (similarity in size) of the blas-tomeres and the degree of cellular fragmentation. A total of 242 embryo transfers in which 4 embryos were transferred were included. Sixty-nine (28.5%) clinical and 62 (25.6%) viable pregnancies resulted. In all cases 4 embryos were transferred, but the number of embryos with even round blastomeres (grade 1) varied from 0 to 4. Statistically, there was no correlation between PR and number of grade 1 embryos transferred. When 4 grade 1 embryos were transferred, the PR was 33.3 versus 28.1% when no grade 1 embryos were transferred. There was, however, a statistical difference in the implantation rate; a higher frequency of multiple gestations occurred when 3 or 4 of the embryos transferred were graded 1:12.7 as compared with 6.7% when < 2 embryos were grade 1. The significance of the degree of cellular fragmentation in the embryos was also assessed. There was no statistical difference in the PR according to the number (0–4) of embryos transferred that did not have fragments (grade A). When 4 grade A embryos were transferred, the PR was 18.2 versus 26.1 % when there were no grade A embryos. Neither implantation nor multiple-birth rates correlated with fragmentation.

It is known that ovarian hyperstimulation and in vitro fertilization are accompanied by a steady increase in circulating estrogen and progesterone far beyond what is normal for young women. We have recently demonstrated that the biologically active fractions of calcium and magnesium in blood are altered depending on when in the menstrual phase a blood sample is drawn in normal cycling women. The serum ionized Ca/Mg ratio is also altered in accordance with the menstrual cycles. This suggests that the sex steroid hormones may modulate serum levels of ionized Mg and the ionized Ca/Mg ratio. We therefore studied the relationships between sex steroid hormones and the concentrations of ionized magnesium and calcium in the blood of hyperstimulated patients. We were able to demonstrate that with each increment in estrogen, a decrease in ionized Mg occurred, and as the progesterone rose in the blood, the ionized Ca/Mg ratio increased. Our results support the idea that serum estrogen and progesterone levels in women modulate the blood levels of circulating ionized Mg and the serum ionized Ca/Mg ratio.

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