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Getting pregnant may seem like a rather mystical process. Once you learn the science and timing, it makes a bit more sense. Still, you may wonder how long it takes to actually conceive after having sex.

The short answer is that the egg and sperm can meet within minutes to up to 12 hours after ejaculation. But to see that second line on the pregnancy test, you still have some hurdles to cross.

Here’s more about how reproduction works (in super simple terms), as well as how to time things and possibly up your odds of getting pregnant.

Related: 10 things to know about fertilization

Fertilization occurs when the egg and sperm meet in the fallopian tube. In order for this to happen, a woman must be in her fertile window. This means that she’s nearing or has reached ovulation — the moment each menstrual cycle when an egg releases from the ovary.

An egg can only be fertilized between 12 and 24 hours from when it is released. After that, it starts to break down, hormones shift, and eventually, a period starts the next cycle.

While it sounds like the chances of catching an egg are pretty slim, consider the numbers. It’s estimated ejaculate contains up to 280 million sperm cells. And under ideal conditions, sperm actually live for several days once inside the reproductive tract.

Any unprotected sex you have within about 5 days of ovulation may leave enough sperm waiting and ready to fertilize. In other words, you may conceive after having sex nearly a week before ovulation if healthy sperm are already hanging out at their final destination.

On the flip side, conception can occur very soon after having sex as well. Experts say that the sperm can navigate the uterus and fallopian tubes to reach the egg as soon as 30 minutes after ejaculation.

Related: The 7-step checklist to healthy, fertile sperm

After fertilization, the new zygote travels down the fallopian tube and goes through tremendous changes. It develops into a morula and then a blastocyst. Once it reaches the blastocyst stage, it’s ready to implant in the uterine lining and continue growing into an embryo.

Implantation is essential to achieve pregnancy. Without it, the blastocyst will break down and be expelled with the rest of the uterine lining during your period.

As for timing, implantation usually happens between days 6 and 10 days after fertilization. Symptoms you may experience are mild and include things like cramping and light spotting. Some women may notice no symptoms at all, however.

Related: Implantation cramping

Once the implanted embryo starts producing hormones (which is right away), pregnancy symptoms may begin.

The earliest symptoms include:

  • Missed menstrual period. If your period is late, you may be pregnant. The hormones produced by the growing embryo signal the brain to retain the uterine lining.
  • Changes in your breasts. Your breasts may feel tender or swollen to the touch due to hormone changes.
  • Morning sickness. While this symptom generally begins a month or so after implantation, it may start sooner for some women. You may experience nausea with or without vomiting.
  • Frequent bathroom trips. Your kidneys go into overdrive during pregnancy because they are tasked with processing extra fluids due to blood volume increases. This means increased urination.
  • Tiredness. You may feel fatigued in early pregnancy. Hormones, again, are at play here. In particular, the hormone progesterone can make you particularly exhausted.

If you experience these symptoms or otherwise think you might be pregnant, it’s a good idea to take a home pregnancy test.

Home pregnancy tests look for human chorionic gonadotrophin (hCG) in your urine. This is produced after the egg implants, but not at detectable levels until 6 to 14 days after fertilization. Your most reliable results will be starting on the day of your missed period, since all cycles are unique.

You can purchase a test at supermarkets, drugstores, or online. Follow all instructions and follow up with your doctor if you have a positive result or if you have a negative result but your period does not start.

In some cases, you may want to go in and have a blood draw, which can detect lower levels of the pregnancy hormone hCG.

Related: Early pregnancy symptoms timeline

To recap, the following things need to happen to achieve pregnancy:

  1. An egg needs to release and get picked up by the fallopian tube.
  2. Sperm needs to be deposited before, during, or immediately after ovulation.
  3. The egg and sperm need to meet (fertilization) to create what eventually becomes a blastocyst.
  4. The blastocyst needs to implant itself in the uterine lining to become an embryo and continue growing into a fetus.

Above all else, you can increase your chances of pregnancy each month by gaining a better understanding of the menstrual cycle and pinpointing your fertile window. You can have sex a million times, but if you’re not in the right part of your cycle, it won’t result in pregnancy.

Sex as early as 5 days before ovulation can lead to conception, but the chances are highest with sex the day immediately before the egg is released.

Some women on a 28-day cycle ovulate around day 14 after the start of their last period. For others, it’s not so predictable. Books like Taking Charge of Your Fertility can help you learn how to track your basal temperature or otherwise understand the signs your body may give, like increased cervical mucus, when ovulation may soon happen.

You may also consider using ovulation predictor kits. These over-the-counter strips detect different hormones in the urine that indicate an egg will soon release.

Don’t want to track too closely? Fertility experts recommend having sex two to three times each week throughout the month. That way, you’ll have a steady stock of fresh sperm.

You may also try things like lying still for 15 minutes after sex and using sperm-friendly lubricants to help those swimmers get where they need to go.

Related: How to increase your chances of getting pregnant

The same advice applies here. Familiarize yourself with your cycle and practice some extra caution during your fertile window. Barrier methods, like male condoms, are around 87 percent effective at protecting against pregnancy.

You may also make an appointment to speak with your doctor about hormonal and non-hormonal birth control options. Birth control pills, for example, are around 93 percent effective at preventing pregnancy. Other options and their effectiveness include implants (99.9 percent), intrauterine devices (99 percent), or shots (96 percent).

Passion happens, though. So, if you find yourself in a situation where you think conception could have occurred, you may also consider taking the morning after pill (levonorgestrel) within 72 hours of having sex.

This emergency contraception is not intended for regular use. It works by preventing or delaying ovulation, so it will not help if ovulation or implantation has already occurred. Brand names include Plan B One-Step and Option 2, and you can find these pills over the counter or online.

It’s a sensitive subject, but don’t be shy about making an appointment for your contraceptive needs. Your doctor can help you choose the right birth control method for your body and your lifestyle.

Related: How often can you take Plan B and other emergency contraception pills?

If you’re trying to get pregnant, don’t be discouraged if it doesn’t happen right away. Of course, this is easier said than done. But the odds are in your favor. Most couples who regularly have unprotected sex get pregnant within 1 year of trying.

If you’re over age 35, consider seeing your doctor if you’ve been trying for 6 months or longer — or if you otherwise have any other concerns about your reproductive health.