"When can I get pregnant, and how long should it take?"

Pregnancy is possible during a fertile window of about six days: the five days before ovulation and the day of ovulation itself. Sperm can survive for several days, but an egg lives for only about a day after it's released.

Ovulation usually happens about 14 days before your next period — not necessarily on day 14. If your cycles are 32 days long, for example, you likely ovulate around day 18.

Not knowing your fertile window is extremely common, and easy to fix. Ovulation predictor kits, cervical mucus changes (clear and stretchy, like egg white) and cycle tracking all help. Having sex every one to two days during the window is enough — you don't need to time it to the hour.

A home pregnancy test is most reliable from the first day of a missed period. Testing earlier is fine, but a negative result may simply mean it's too soon.

Even with perfect timing, the chance of pregnancy in any single cycle is well under 50% for healthy couples. Most couples — about 85% — conceive within a year.

Three months without a positive test is normal, not a warning sign. General guidance is to talk with a fertility specialist if you haven't conceived after:

• 12 months of trying if you're under 35
• 6 months if you're 35 or older
• Right away if you're over 40, or have very irregular or absent periods, known endometriosis, prior pelvic infection, or a partner with known fertility concerns

If you've reached that point, see Trouble conceiving for what an evaluation looks like and the questions to ask.

For most methods — the pill, patch, ring, hormonal or copper IUD, and implant — fertility returns quickly, often within the first cycle or two. Years of use don't harm future fertility.

The contraceptive injection (Depo-Provera) can delay the return of ovulation for several months, sometimes up to a year or more after the last shot.

If your periods haven't returned within about three months of stopping a method other than the injection, let your clinician know. Birth control can mask an underlying cycle irregularity, such as PCOS, that was there all along.

Egg number and quality decline with age, gradually through the early 30s and more steeply after about 37. That means it may take longer to conceive and the chance of miscarriage is higher — not that it can't happen.

Many women conceive naturally in their late 30s and 40s. The practical difference is time: at 35 and older, it's worth seeking help sooner rather than waiting a full year.

A preconception visit is especially valuable after 35 — to check health conditions, review medications, and discuss screening options for a future pregnancy.

The baby's brain and spinal cord form in the first weeks — often before a positive test. That's why prenatal vitamins are recommended at least one month before you start trying.

• Folic acid, 400 mcg daily — lowers the risk of neural tube defects. Some women need a much higher dose (for example, after a prior affected pregnancy or with certain seizure medications); ask your clinician.
• Iodine, about 150 mcg — for the baby's brain and thyroid; missing from many prenatals.
• Choline — important for the baby's developing brain, yet most prenatal vitamins contain little or none. Why choline matters.
• Vitamin D and DHA (omega-3) — commonly recommended; needs vary.

This is one of the most common worries — and you're far from alone. Start now. Most pregnancies where prenatal vitamins began after the positive test are healthy, and your clinician can talk through any specific concerns.