What causes bladder exstrophy?

We don’t know what causes exstrophy and to date medical science has no explanation for why an embryo may develop bladder exstrophy. The problem occurs 4 to 8 weeks after a woman gets pregnant. This is when organs, muscles and tissues begin to form layers that separate, divide and fold. Exstrophy is not caused by something the mother did or did not do while she was pregnant. It does not run in families (it is not hereditary).