This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
We consider iron not a direct, but an indirect emmenagogue, by virtue of its improving the blood-condition; but since the continued use of the mineral can cause congestion of the pelvic, as well as of other organs, it becomes an important question as to whether its use is admissible or is dangerous during pregnancy. Certainly the perchloride has been in frequent popular use as an abortifacient, but the evidence of its power for this purpose is not cogent (v. p. 147). Its use has often furnished occasion for prosecutions, but few cases of its really causing abortion are recognized, and, in many of these, as well as when the sulphate has been used, the effect seems to have followed from violent irritation of the intestinal canal. It is true that cases in which abortion is deliberately produced would not, as a rule, find their way into the public press; but, allowing for this, I find a general impression gaining ground that iron may be taken during pregnancy without injurious effects.
Ramsbotham and Barnes recommend it, the latter stating that he has never seen harm from it (Lancet, i., 1874, p. 768). It was stated during a recent trial that 10-gr. doses of ammonio-citrate of iron were dangerous to a pregnant woman, but Dr. Woodman contradicted this from his own experience, and Dr. Graily Hewitt said that he and others constantly prescribed it during pregnancy (British Medical Journal, i., 1870). Dr. Bassett brought before the Obstetrical Society many cases illustrating the value of the citrate and tartrate of iron in averting miscarriage and serious hemorrhage in delicate women, and there seems to have been no difference of opinion upon the subject (Lancet, i., 1874, p. 768): he considers that the addition of an alkali to the iron medicine renders it better borne, and points out that aperients should be given occasionally during the course. I can corroborate the experience of Dr. Bassett, and I think that the neutral preparations of iron are the most suitable during pregnancy, though some observers speak well even of the perchloride (Day: British Medical Journal, i., 1870). Trousseau remarks that iron has no direct emmenagogue power, and Hirtz has never seen any objection to using iron in the anaemia of pregnancy, though he has not found it very useful ("Diet, de Med."); altogether we must conclude that the older fears of injury from its moderate medicinal use were unfounded.