The objective of this retrospective study was to determine the factors influencing the occurrence f multifetal pregnancy in in vitro fertilization and embryo transfer(IVF-ET) program, and this to avoid the unwanted maternal and perinatal outcomes
of
multifetal pregnancy. These various factors were statistically analyzed and compared between 53 singleton and 35 multifetal pregnancies in 428 IVF-ET cycles after controlled ovarian hyperstimulation(COH) at Seoul National University Hospital from
January to December, 1994.
The clinical pregnancy rate(PR) per ET was 20.6% with the multifetal PR of 39.8%. there were no significant differences in age of patients, age of husbands, duration of infertility, cause of infertility, number of previous IVF-ET trials, serum
peak
estradiol(E2) level, number of oocytes retrieved, and fertilization rate between singleton and multifetal pregnancies. The major factors influencing the occurrence of multifetal pregnancy were elucidatel as 1) number of embryos transferred, 2)
proportion of top grade 1 and 2 in grading of embryos, and 3) cumulative embryo score(CES), Multifetal pregnancies over triplet occurred only when the number of embryos transferred was 6 or more and top grade of embryos was 1,2 or 3. The
significant
linear correlation was observed between top grade of embryos and clinical and multifetal PR. The ground clinical and multifetal PR were progressively increased with CES, with the highest multifetal PR in group with CES≥96. The high risk group of
multifetal pregnancy was that 1) number of embryos transferred was 6 or more, 2) top grade of embryos was 1 or 2, and 3) CES was 96 or more. The lower group was that 1) top grade of embryos was 4 or, 5, and 2) CES was 10 or less and 145 or more.
In conclusion, to maximize the clinical PR and prevent the multifetal pregnancy simultaneously in IVF-ET, the new options in the protocol of IVF-ET program should be adopted: 1) avoiding the high risk group of multifetal pregnancy and the lower
PR
group, and 2) using assisted reproductive technology(ART) such as cryopreservation, conculture in vitro, and assisted hatching of embryos.
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