The best time to try to get pregnant is during a six-day window each menstrual cycle: the five days before ovulation and the day of ovulation itself. This is your fertile window, and it exists because sperm can survive inside the body for up to five days, while a released egg lives for less than 24 hours. The highest pregnancy rates occur when sperm and egg meet within four to six hours of ovulation, so having sex in the days leading up to ovulation gives sperm time to be in position.
How to Find Your Fertile Window
Ovulation typically happens about 12 to 14 days before the start of your next period. If you have a 28-day cycle, that puts ovulation around day 14. But cycles ranging from 21 to 35 days are all considered normal, which means ovulation day shifts accordingly. A woman with a 32-day cycle likely ovulates around day 18 to 20, while someone with a 25-day cycle may ovulate as early as day 11.
The key detail: you count backward from when your next period is expected, not forward from your last one. If your cycles are irregular, this math gets harder, and tracking tools become more useful.
Ovulation Prediction Tools
Ovulation predictor kits (OPKs) detect a hormone surge in your urine that precedes ovulation. The onset of this surge typically happens about 36 hours before ovulation, and the peak occurs 10 to 12 hours before the egg is released. A positive result means you’re likely to ovulate within the next day or two, making it an ideal time to have sex.
Cervical mucus is another reliable signal. As you approach ovulation, discharge changes in a predictable pattern. At peak fertility, it becomes transparent, stretchy, and slippery, similar to raw egg white. This type of mucus helps sperm travel and survive, so when you notice it, you’re in your most fertile days.
Basal body temperature (BBT) tracking works differently. Your resting temperature rises slightly, less than half a degree Fahrenheit, after ovulation. You can confirm ovulation occurred once you see three consecutive days of elevated temperature. The limitation: by the time your temperature rises, ovulation has already happened. BBT is better for learning your cycle patterns over several months than for timing sex in the current cycle. Pairing it with mucus tracking or OPKs gives you both a forecast and a confirmation.
How Often to Have Sex
You don’t need to time things down to the hour. Because sperm survive for days inside the reproductive tract, having sex every one to two days during your fertile window covers your bases well. Starting a few days before you expect to ovulate means sperm are already waiting when the egg arrives.
There’s no evidence that specific positions improve your chances of conceiving. Healthy sperm begin swimming immediately after ejaculation, so lying with your feet in the air afterward doesn’t help either. What matters is frequency and timing within the fertile window, not technique.
How Age Affects Your Chances
A large preconception study tracked thousands of couples and measured per-cycle conception rates by age. Fertility stays relatively stable through the early 30s, then drops more noticeably. Compared to women ages 21 to 24 (the reference group), per-cycle conception odds were:
- Ages 25 to 33: about 87 to 91% of the reference group’s rate, a modest decline
- Ages 34 to 36: about 82% of the reference rate
- Ages 37 to 39: about 60% of the reference rate
- Ages 40 to 45: about 40% of the reference rate
In cumulative terms, roughly 75 to 79% of women in their late 20s to mid-30s conceived within 12 cycles of trying. That number dropped to about 67% for women 37 to 39 and around 56% for women 40 to 45. These numbers reflect natural conception without fertility treatment.
The takeaway isn’t that getting pregnant after 35 is unlikely. It’s that each cycle carries a lower probability, so it may take more months of trying. If you’re under 35 and haven’t conceived after 12 months of regular, well-timed sex, a fertility evaluation is recommended. If you’re over 35, that timeline shortens to 6 months. Women over 40 benefit from an evaluation before they start trying, since earlier intervention tends to improve outcomes.
Putting It All Together
The practical strategy is straightforward. Start by getting a rough sense of when you ovulate, either by tracking your cycle length or using OPKs. Have sex every one to two days during the five days before and the day of expected ovulation. Pay attention to cervical mucus as a real-time fertility signal, and consider BBT tracking if you want to confirm your patterns over a few months.
Most couples who time intercourse to the fertile window conceive within several months. The process works best when you treat it as a window of days rather than trying to pinpoint a single perfect moment. Sperm are designed to wait, and giving them a head start by having sex in the days before ovulation is the single most effective thing you can do to improve your chances each cycle.