I have a theory on why pregnant women die on the island. Is because the four-toed statue was destroyed. The statue was the Egyptian godness Tawaret. Tawaret was the symbolism of a pregnant woman. So in the episode "Lafleur" amy successfully gave birth to her baby. so that means the statue was still exist and up. Now when juliet came the women were dying. so the statue was destroyed. Now your probably wondering how did claire have her baby on the island? well claire was pregnant "off" the island. so the women were pregnant "on" the island so they died. Thats just my theory . i dont think its not true.