IVF: Two embryos lead to more pregnancies than three.

Research has been released which gives further understanding on how many embryos to transfer in order to increase the chances of an IVF cycle. The conclusions suggest there is no increased chance of a positive pregnancy when a third embryo is transferred.

The study was conducted by Scott Nelson and Debbie Lawlor from Bristol University. They considered IVF cycles which took place in the United Kingdom between 2003 and 2007. Each of the 124,148 IVF cycles which were considered (these included 33,500 live births) were stratified into groups according to the age of the mother. This allowed direct comparisons to be made between IVF patients over 40 years to those under the age of 40. Inclusion criteria into the study did not discriminate on the causational factors leading to each infertility case. The women’s ages ranged between 18 to 50 years of age.

The results for the group of women under the age of 40 indicated that when a third embryo is transferred, the live birth rate was 25%. This is significantly lower than the 33% live birth rate, when only two embryos are transferred. In contrast, the women over the age of 40 showed no difference in the live birth rate when two or three embryos were transferred.

The research hypothesized that the higher miscarriage rate when three embryos are transferred to women younger than 40 may be due to the added probability of one miscarrying foetus jeopardizing the entire pregnancy.

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