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Blastocyst Transfer Improvements May Eliminate Multiples.

Transfer of two blastocysts during in vitro fertilization results in about the same pregnancy rate as transfer of three and eliminates the risk of higher-order multiple gestations, according to results of a recent study.

Blastocyst transfer also can boost pregnancy rates in women who have failed to become pregnant after undergoing at least three traditional in vitro fertilization (IVF) procedures, reported investigators in a second study.

In traditional IVF, cleaving embryos are transferred to the uterus after 3 days of culturing. However, improvements in culture media have made it possible to grow embryos to the blastocyst stage for transfer on day 5 or 6, more closely following what happens in nature.

In spontaneous pregnancy, cleaving embryos develop in the fallopian tube, but blastocysts are found in the uterine cavity. "With blastocyst transfer, it is possible that results could be improved because cleavage-stage embryos are not introduced into the uterine cavity," Dr. David R. Meldrum said in an editorial accompanying the studies (Fertil. Steril. 72[2]:216-17, 1999).

The improved efficiency of blastocyst transfer allows physicians to transfer only two embryos, eliminating the risk of higher-order pregnancies.

"We now have the means to solve the most important problem that [assisted reproductive technology] has faced over the years," said Dr. Meldrum of the Reproductive Partners Medical Group in Redondo Beach, Calif.

In the first study, which included 55 women, 53% of cultured embryos developed into blastocysts, and 32 women had viable pregnancies, defined as fetal cardiac activity on ultrasound performed at about 7 and 9 weeks of gestation, said Dr. Amin A. Milki and his associates at Stanford (Calif.) University.

The pregnancy rate was 76% in the 29 women who received two blastocysts and 75% in the remaining women who received three (Fertil. Steril. 72[2]:225-28, 1999).

A total of 39% of the pregnant women in the two-blastocyst group had twin gestations, while 79% of those in the three-blastocyst group had twin or triplet gestations.

The procedure was offered to IVF candidates who were at increased risk of multiple gestations, defined as having more than three good-quality embryos on the third day of culture. "The pregnancy and implantation rates among this group have been so reassuring that we now feel confident in offering blastocyst transfer to a larger population," the investigators said.

That larger population may include women who have not been able to get pregnant with conventional IVF. Blastocyst transfer more than quadrupled pregnancy rates in women who had already failed to get pregnant after at least three IVF cycles, said Dr. Jose R. Cruz and his associates at the George Washington University Medical Center in Washington.

In their retrospective study pregnancy was achieved in 40% of 15 patients who agreed to blastocyst transfer, compared with 9% of 22 patients who underwent conventional IVF (Fertil. Steril. 72[2]:218-20, 1999).

A third study suggests that blastocyst transfer seems to favor male infants, said Yves J.R. Menezo, Ph.D., of the Marcel Merieux Foundation in Bron, France, and his associates.

In a cohort of 383 births from freshly grown blastocysts, 58.7% were boys and 41.3% were girls. However, this did nor hold true for children born from frozen-thawed cocultured blastocysts (Fertil. Steril. 72[2]:22 1-24, 1999).

Blastocysts are harvested at day 5 or 6, driving a preference for early-forming blastocysts, which are more likely to be male embryos, the investigators said.
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Title Annotation:multiple gestation
Publication:Family Practice News
Geographic Code:4EUFR
Date:Oct 15, 1999
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