Screening IVF embryos for genetic defects increases the death risk of multiple birth babies five times, a study has found.
But the procedure, known as pre-implantation genetic diagnosis (PGD), appears to be harmless for singletons.
PGD involves removing one or two cells from an embryo to test it for abnormalities and diseases.
There have been concerns the test might itself adversely affect babies created through In-Vitro Fertilisation (IVF).
The largest and longest running study of children born after PGD suggests that such fears are unfounded, for singletons at least. However researchers found in the case of multiple pregnancies, PGD increased the risk of death around the time of birth five-fold.
The findings were published yesterday in the journal Human Reproduction.