Can you get pregnant on your period? What the data shows

The answer turns on how long sperm survive and when you ovulate. ACOG's patient guidance says sperm can live in the body for as long as 5 days, while an egg survives for about 12 to 24 hours after ovulation (ACOG, 2023). The NHS says sperm can survive in the fallopian tubes for up to 7 days after sex (NHS, 2023). The UK figure stretches the fertile time a little earlier in the cycle, so this guide gives both.

Can you get pregnant while on your period?

You can get pregnant during your period only if the sperm from that sex are still alive when ovulation comes. Pregnancy is possible from sex in the six days that end on the day of ovulation (Wilcox et al., 1995), and ACOG puts the window at about 6 days, from 5 days before ovulation to 1 day after it (ACOG, 2023). In a regular 28-day cycle that window falls in the middle of the cycle, well after the period. In a short cycle it can start during the period: ACOG gives ovulation around day 7 in a 21-day cycle (ACOG, 2023), which puts the start of the fertile window on about day 2, by our arithmetic, while a period can last up to 7 days (NHS, 2023).

That is why the NHS says it is possible, although not very likely, to get pregnant soon after a period if you ovulate early or have a short cycle (NHS, 2023). So, can you get pregnant on your period? The data say the chance is small and depends mostly on the length of your cycle.

What are the chances of getting pregnant on your period?

A study of 221 women who were trying to conceive dated ovulation from daily urine hormone samples and worked out, for each day of the cycle, the share of women who were in their fertile window (Wilcox et al., 2000):

Being in the fertile window is not the same as conceiving. In the same women, the chance of pregnancy from sex on a single fertile day ranged from about 10 in 100 five days before ovulation to about 33 in 100 on the day of ovulation (Wilcox et al., 1995). Sex during a period usually falls on the early, lower-chance edge of the window, when it falls inside it at all. So the chances of getting pregnant while on your period are low. How likely is it to get pregnant on your period in your own cycle? That depends mostly on how early you ovulate. The guide to the chances of getting pregnant gives the figures for a whole cycle.

Cycle length makes a large difference. Among women with regular cycles, an estimated one third of those whose cycles usually lasted 27 days or less had reached their fertile window by the end of the first week, compared with only 7 in 100 of those with longer cycles (Wilcox et al., 2000).

Can you get pregnant right after your period?

Yes, and it is more likely than during it: you can get pregnant after your period whenever ovulation comes early. The NHS says it is possible, although not very likely, to get pregnant soon after your period finishes if you ovulate early or have a short menstrual cycle (NHS, 2023). By day 7 of the cycle, about 17 in 100 women in the study above were already in their fertile window (Wilcox et al., 2000), and a 5-to-7-day period ends right around then.

Can I get pregnant 2 days after my period?

It is possible, and in a short cycle it is quite likely to be a fertile day. If your period lasts 5 days and your cycle is 21 days, 2 days after your period is day 7, the day ACOG gives for ovulation in a 21-day cycle (ACOG, 2023). In a 28-day cycle the same day falls about a week before ovulation, outside the fertile window for most women. Those dates are our arithmetic from ACOG's rule, and real ovulation days vary.

Can you get pregnant the day after your period?

Possibly, for the same reason. In a study of 141 women with regular cycles, 95 in 100 cycles had all six fertile days somewhere between day 4 and day 23 (Fehring et al., 2006), so the days just after a period can fall inside the window in some cycles.

How many days after your period can you get pregnant?

Count from the start of the period, not its end, and work back from the next one. ACOG's patient guidance puts ovulation about 14 days before the next period starts, so around day 7 in a 21-day cycle and around day 21 in a 35-day cycle (ACOG, 2023). Taking the fertile window as the six days ending on ovulation day gives:

ACOG also counts the day after ovulation as fertile (ACOG, 2019), which adds one day to the end of each window. The table is a guide, not a promise: in cycles that were exactly 28 days long, ovulation came exactly 14 days before the next period in only about 1 in 10 (Wilcox et al., 2000). The ovulation calculator does this sum for your own dates, which is what people looking for a calculator for how many days after my period I can get pregnant usually want, and the guide to the most fertile days explains why the window moves.

Can you get pregnant right before your period?

Can you get pregnant before your period? Right before it is usually the least likely time, but not a safe one. Even women who regarded their cycles as regular had a 1 to 6 in 100 chance of being in their fertile window on the day their next period was expected (Wilcox et al., 2000). Late ovulation happens in any cycle, and when it does, the period comes later than expected too.

Can you get pregnant 2 days before your period?

It is unlikely if ovulation came at its usual time, because the egg survives only 12 to 24 hours (Office on Women's Health, 2025) and the time from ovulation to the next period is usually around 10 to 16 days (NHS, 2023). The same holds if you ask whether you can get pregnant the day before your period: women with regular cycles had a 1 to 6 in 100 chance of being in their fertile window on the expected day (Wilcox et al., 2000). Can you get pregnant 5 days before your period? It is similarly unlikely in a regular cycle, for the same reasons.

Can you get pregnant a week before your period?

It is possible. In a 28-day cycle a week before the period is day 21, and at least 10 in 100 women with regular cycles were in their fertile window on every day from day 6 to day 21 (Wilcox et al., 2000).

Using your period to avoid pregnancy

A period calendar is not a reliable method of contraception on its own. ACOG reports that when fertility awareness methods are used to prevent pregnancy, 12 to 24 in 100 people become pregnant in the first year of typical use, and fewer than 1 to 5 in 100 with perfect use (ACOG, 2019). It suggests learning the methods from a qualified teacher (ACOG, 2019). The period calculator predicts when periods are due; it is not a method of birth control.

When to take a pregnancy test

The NHS says most pregnancy tests can be used from the first day of a missed period, and that if you do not know when your period is due, you can do a test 21 days after you last had unprotected sex (NHS, "Doing a pregnancy test", 2022). The pregnancy test calculator works out the earliest reliable date from your cycle. Bleeding in early pregnancy is not a period; the guide to implantation bleeding covers it, and the guide to ovulation symptoms describes the signs that show when ovulation is near.