Laser bursts help 'hatch' embryos

Embyros can be stimulated using lasers

Firing laser beams at embryos before implanting them is a safe way of improving IVF success rates, say Hungarian scientists.

The tiny bursts of laser light drill through the outer membrane of the embryo immediately before it is placed in the uterus.

IVF often fails because the fertilised embryos are not able to implant themselves into the wall of the womb to continue their development.

Lasers provide the quickest, most effective and safest hatching technique

Dr Katalin Kanyo

The precise reasons why any particular embryo fails to implant are not known.

However, the "tunnel" in the shell created by the laser seems to help the embryo escape and increase the chance of successful implantation.

Similar techniques are also being used to help test embryos for genetic abnormalities prior to implantation.

The embryonic membrane is on average only 18 millionths of a metre thick, and the scientists from the St John Hospital in Budapest used an infrared diode laser in bursts of 20-30 milliseconds.

Unlike earlier attempts to use a laser, the beam is applied at an angle, meaning only the edge is in contact with the shell, making a hole between 4.5 and 20 millionths of a metre.

Cell damage

The new technique limits the exposure of the embryo to laser radiation, which could cause damage to the cell structure or the genetic material held within.

The process has to be completed quickly - the embryo has to be transferred to the womb within a minute of using the laser.

Other scientists have used both tiny probes to create the hole, and chemicals, but Dr Katalin Kanyo, who led the project, said: "We did not find any higher risk of congenital malformations or chromosome abnormalities.

"Our studies show that lasers provide the quickest, most effective and safest hatching technique."

At the St John Hospital, lasers were safely used in fertility treatments leading to 134 births between December 1998 and December 1999.

The technique was also used to help "problem" patients, women over the age of 35, some of whom had previously had three failed IVF attempts.

On average, a third of the women became pregnant.