Can iron be teratogenic?

Several kinds of evidence indicate that elevated iron during the 3–8 week embryonic (organogenesis) period of human gestation may be teratogenic. (1) In the embryonic period, the natural maternal absorption of food iron is 30% below the estimated daily iron loss. (2) As compared with maternal serum, embryonic fetal coelomic fluid contains only one-fourth as much iron but nearly six times the quantity of the iron withholding protein, ferritin. (3) In the embryonic period, intraplacental oxygen pressure is 2–3 times lower than in the subsequent fetal growth period. (4) Iron is a strong inducer of emesis which peaks in the embryonic period. (5) In a murine gestation model, iron was neurotoxic at a sharp peak of 8–9 days. Thus it would be prudent, in human pregnancy, to delay any needed iron supplementation until the embryonic period has been completed.