laboratory artifact

[Eway]

...When their report of the first successful fertilization of a human egg in vitro was published in Science, scientists were skeptical. ... Maybe, critics said, the observed cleavage was just a laboratory artifact, something that can happen to unfertilized eggs in a petri dish -- a kind of reflex cell division that will never lead to a healthy, normal child.

What is a "laboratory artifact"?

[svforumer]

artifact: any object made, modified, or used by people.
laboratory artifact: any object made, modified, or used by people in laboratory.

[Casiopea]

In addition,

'arte' from Greek meaning, art, and 'fact' from Greek meaning, make. Artefact, also spelled artifact, means an object that's not created by nature; it's human made, or crafted by human intervention. Note, the paragraph you provided gives us a really big clue about the meaning of 'laboratory artifact':

". . . something that can happen to unfertilized eggs in a petri dish -- a kind of reflex cell division that will never lead to a healthy, normal child."

Both fertilized and unfertilized eggs divide. The former by sperm, the latter by themselves in a petri dish. Human intervention: placing the unfertilzied eggs into a petri dish thereby altering their environment, and causing the cells to divide, which mimics the process a fertilized egg undergoes.