Intrauterine exposure to copper IUDs and prenatal development in the rat

Small coils of copper wire releasing 4-5 microgram copper/coil/day were inserted between each implantation site of one uterine horn of rats on Day 9 of pregnancy. The coils remained in the uterus until Day 21 of pregnancy when the animals were killed and the uterine contents examined. There were no significant increases in the incidence of congenital malformations or growth retardation in fetuses from horns containing copper coils in comparison with fetuses from unoperated horns, sham-operated horns, or horns containing inert stainless-steel coils. Intrauterine mortality rates were significantly higher in horns containing copper coils (19-24%) than in sham-operated or unoperated horns (0-8%), but not significantly different from that in horns containing inert steel coils (25%). In rats killed on Day 22 of pregnancy, after insertion of copper coils into both uterine horns on Day 9, there were significant increases in fetal brain, fetal liver, placenta and uterine copper levels in comparison with rats containing steel coils or no coils. Maternal plasma and liver copper levels were not elevated by intrauterine copper coils.