My wife is 13 weeks pregnant after IVF , as per first trimester scan size, herat beat, movement etc are fine, since last 3 days she has been advised Corcium Lupin a calcium tablet and Biofer XT an iron tablet in addition to the Folvite follic acid tablet she was having for last month. Yesterday she had a trace of blackish stool and today the stool is blackish in color. She is worried since this is the first time she is having this colored stool. Please advice.