Best Days to Get Pregnant With a 37-Day Cycle
If your cycle is 37 days long, your chance of pregnancy is highest on cycle days 21 to 23: the two days before ovulation and ovulation day.
| Cycle length | 37 days |
|---|---|
| Likely ovulation day | Cycle day 23 (range 21–25) |
| Fertile window | Cycle days 18–23 |
| Most fertile days | Cycle days 21–23 |
| Next period due | Cycle day 38 |
Why the days before ovulation matter most
Studies of couples trying to conceive found that sex in the one to two days before ovulation is linked with the highest pregnancy rates. Sperm need some time to travel and become ready to fertilise an egg, so having them in place before the egg is released helps.
How often to have sex
Every day or every other day during the fertile window works well. There's no need to save up sperm, and frequent sex in this window doesn't lower the chances.
Cycles longer than 35 days fall outside the typical adult range of 21 to 35 days. Long or unpredictable cycles can be a sign that ovulation isn't happening every month, for example with polycystic ovary syndrome (PCOS) or thyroid problems. If your cycles are regularly 37 days or longer, it's worth talking to a doctor, especially if you're trying to conceive.
Ovulation Calculator: Predict ovulation days for your next three cycles.
Open the calculatorThis article is general information, not medical advice. Talk to a doctor or midwife about your own pregnancy or fertility.