Simple Answer-Yes! She can get pregnant immediately after her period.
When you have sex without any form of contraception, pregnancy can occur because sperm can still stay alive long enough to fertilize a woman’s egg that is released up to 5 days after the man’s ejaculation. Now in some women, their menstrual cycle is so short that ovulation (the release of a fertile egg from the ovaries) may happen even while her menstrual blood is still flowing.
If she has a short 21/22 day cycle and typically has her period flow for 5 to 7 days, she could ovulate from Day 5 and so she can certainly get pregnant if you have unprotected sex immediately after her period. Also, many factors like stress or medication can also alter her previously regular 28/30 day cycle resulting in early or late ovulation.
Fertility period in women
A woman is very fertile around 6 days in every month; which is, the five days before ovulation and not more than 24 hours after ovulation occurs. The best time to get pregnant is within these fertile days, especially 1-2 days before ovulation.
Most women ovulate from 12 to 16 days before the expected date of their next period. Knowing the fertile periods and safe periods in each menstrual cycle can be hard to keep up with and usually requires at least 3 months (preferably longer) of menstrual cycle monitoring to correctly determine a woman’s average cycle length. This means that without knowing when your next period typically occurs, calculating ovulation date or window can be tricky especially if you start counting from your last period. One common myth is that ovulation happens 14 days after you start your menstrual period. This is not true.
So what do you do if you are not ready for pregnancy?
If you want to do fertile period monitoring, we recommend you only attempt this if she gets regular periods and after getting an ovulation test kit to double-check. However, if she has irregular periods, don’t bother because fertility monitoring will not work for you.
Take a decision to use contraceptives like condoms, pills, injections, implants, Copper IUDs, etc. in order to confidently prevent unwanted pregnancies.
If you think your woman might be pregnant, wait until she ‘misses’ her period and order a pregnancy test to confirm.