This means that fewer than one in 100 women who use an IUD will get pregnant in one year. IUDs with less copper will be less effective. ”
وَكُلَّمَا قَلَّتْ كَمِّيَّةُ ٱلنُّحَاسِ فِي ٱللَّوْلَبِ ،‏ خَفَّتْ فَعَّالِيَّتُهُ » .‏