1.   He used a tiny doll-sized optical instrument to penetrate the amniotic sac of the plump twin.

2.   Previously, surgeons severed all vessels crossing the membrane dividing the amniotic sacs to stop the piracy.

3.   The bladder on the puny baby was working, refilling the dry amniotic sac.

4.   The method would spare many women the need for a definitive test called amniocentesis, in which a needle withdraws fluid from the amniotic sac.