I didn't get nosebleeds in my first trimester but I did get diarrhoea for a few days. What kind of supplements are your wife taking? If it is folic acid, it is unlikely to cause nosebleeds and diarrhoea. Were any other supplements prescribed by her OBS? If they were, she needs to inform her OBS of her symptoms. Pregnant women are usually required to take multivitamins and fish oil when they enter their second trimester.