I was prescribed Norethisterone from day 14-25 of my cycle in preparation for a round of natural IVF. I ended up with a large follicle and LH surge on day 9, so we have had IUI instead as my consultant feared we would lose the egg waiting for the trigger for the IVF. I have just realised that I only took one Norethisterone each day, rather than the two prescribed. Despite running to a 28 day cycle, the follicle was enlarged and my LH results were very high on day 9, indicating premature ovulation. Would taking only one Norethisterone have affected the timing of my ovulation?