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31-01-2010 | Gynaecology | Article

Spontaneous cycle superior to hCG-induced cycle for frozen-thawed embryo transfer


Journal abstract

MedWire News: Study findings suggest that women undergoing frozen-thawed embryo transfers in natural cycles are more likely to achieve an ongoing pregnancy if the cycle is not controlled with human chorionic gonadotropin (hCG).

Three-day embryos were transferred in 124 women with natural cycles and spontaneous luteinizing hormone (LH) surge and in 63 women whose natural cycles were being controlled with hCG.

The embryo transfer was performed 5 days after the spontaneous LH surge in the former group and 5 days after administration of 5,000 IU of hCG in the latter group. At this time, endometrial and follicle thickness were at least 7 mm and 17 mm, respectively.

LH rise (without progesterone rise) occurred in 36.5 percent of women receiving hCG. Of these, only 4.3 percent became pregnant.

“hCG and LH share the same receptor and their simultaneous presence could adversely affect pregnancy,” say Human Mousavi Fatemi (Free University Brussels, Belgium) and co-authors.

The researchers terminated the study early, as interim analysis found a significantly higher ongoing pregnancy rate in the spontaneous LH group compared with women in the hCG group, at 31.1 versus 14.3 percent.

Fatemi and team say their findings “demonstrate the superiority of the natural cycle to a natural cycle controlled by the administration of hCG for planning the frozen-thawed embryo transfer.”

MedWire ( is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Ingrid Grasmo