This situation can appear due to A-vitamin lack in the egg embryo, or to the hardening of the internal membranes of the egg peel, due to little humidity.

For the first case it's necessary to provide extra supply of this vitamin(A). There are several laboratories that have available products rich in vitamins AD3E. These products besides they suppress the lack in A-vitamin, they supply the vitamin D and E that also are very importance during the breeding period.

Particularly I advise the use of cod-liver oil.