Usually the cervix returns to a non-fertile (closed, low, hard) position just after ovulation. You may, however, notice that it exhibits some fertile characteristics even after ovulation. This is because some estrogen may be produced by the corpus luteum during your luteal phase. If your chart is showing a clear and sustained thermal shift and ovulation is clearly detected on your chart, you need not consider yourself fertile. If, however, you are noticing that your cervix is exhibiting fertile characteristics and your thermal shift is not dramatic or clear, you should consider that you could be fertile and keep on having intercourse so you don't miss a chance.