Understanding Births in the Amniotic Sac: What Does 'En Cal' Mean?

Question
My daughter in law just gave birth to a beautiful boy.  One of the attending nurses stated that the baby had been born "in a sack".  Just what does that mean, exactly?  She also stated that this was very special.

Answer
Most of the time, prior to delivery of the baby, the membranes surrounding the baby (amniotic sac( rupture ("breaking the water") and then the baby is delivered. However, at times, the baby is delivered ("en cal")=or in the sac. The amniotic sac has not ruptured and the baby,still within the sac, is delivered. Then the membranes are ruptured once the baby is delivered. This has no significance as to the health of the baby.