Many women notice that sometimes stress or illness leads to getting their period late. You can generally tell whether your period will be delayed based on when you get sick. If you haven't ovulated yet, getting sick or stressed may delay ovulation, and as a result, your period may be late. If you have ovulated, your period will be right on time (provided you aren't pregnant!). The luteal phase, the time between ovulation and your next period, is a very consistent length and isn't interrupted by minor illness.
Of course, sometimes it isn't this straightforward, because you get sick right around when you'd expect to ovulate. Many things can effect your fertility signs when you're sick:
- Fever makes temperature readings unreliable.
- You may not be sleeping well, or you may be waking up frequently, making waking temperature unreliable.
- Medication can effect waking temperature.
- Medication to treat congestion (mucinex, antihistamines) can effect cervical fluid.