I don't believe this.

Here is an excerpt from an article on BBC.com:

More evidence has emerged that babies born from frozen embryos are healthier than those that develop from fresh embryos, researchers say.

Three studies presented to a US fertility conference found frozen embryo babies were less likely to be premature and under weight.

Previous research has suggested this is down to only the strongest embryos surviving the freezing process.
Fertility experts said more work was needed on the issue.