Hi there I understand your concern...you must have undergone iui due to failure of natural pregnancy... Progesterone is very much necessary to maintain pregnancy....Progesterone is a hormone which is normally produced by the ovaries, both in non pregnant women and in pregnant women. In pregnant women, the progesterone production increases greatly, this is due to the formation of corpus luteum, and once the placenta forms that also produces progesterone, because progesterone is required for maintaining the pregnancy till term....for further details Consult your treating doctors.