An Illustration of Fertilization

How Many Days After Sex Is Conception?

It takes time for sperm to travel from the testis, past the cervix and into the fallopian tubes where an egg is waiting. Then, fertilization and implantation must take place.

When trying to conceive, it’s important to understand the timeline of how the process works and how to maximize your chances. The first step is to get in tune with your menstrual cycle and pinpoint your fertile window.


Fertilization happens when sperm meet an egg and fertilize it. This occurs mainly in the fallopian tubes that connect the ovaries and uterus. It’s a complex multistep molecular process. The sperm’s DNA mixes with the egg’s pronuclei, turning it into a fertilized zygote.

Women are most fertile around the time of ovulation. Ovulation usually happens 12 to 14 days before your period starts, but it can happen earlier or later. If you have sex during this time, your chances of pregnancy are very high.

Sperm can live up to five days inside a woman’s reproductive tract, so you could get pregnant even if you have sex only hours before or after ovulation. However, an egg can only be fertilized once.

Once an egg has been fertilized, it travels down the fallopian tube to your uterus, where it implants in the lining of your womb (the endometrium). Then the fertilized egg starts dividing rapidly to become a blastocyst. The blastocyst then secretes a hormone called human chorionic gonadotropin, or hCG. This hCG can be detected in your pee by an at-home pregnancy test. If you’re trying to conceive, a positive hCG result means that the fertilized egg successfully implanted and that you’re pregnant. But this only happens about 25% to 30% of the time. It’s important to use birth control until you get a clear, reliable result from a home pregnancy test.

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Once sperm reach your egg, it takes a few days for them to fertilize. The fertilized egg then has to travel to your uterus and attach itself to the lining, a process called implantation. Implantation usually triggers rising levels of key pregnancy hormones, like estrogen, progesterone, and hCG.

If you have regular sex every other day during your most fertile window, you might get pregnant in as few as five days after fertilization. However, some sperm can survive up to three days inside female reproductive organs, so you could get pregnant even sooner.

Most women ovulate about 14 days after the start of their menstrual cycle. You can figure out when you’re ovulating by watching for changes in your cervical mucus. It’s also possible to use an ovulation monitor or app to get more accurate intel.

Many people can conceive with in vitro fertilization (IVF). During IVF, an egg from either the intended parent or a donor is mixed with sperm in a lab. Afterward, the created embryo is placed in the uterus that will carry the pregnancy to term. Conception still happens, but it involves a lot more steps and is not as reliable as natural conception.

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Gestational Age

Gestational age is a calculation of the length of pregnancy, based on the first day of the last menstrual period (LMP). It estimates when a person may be due to give birth and helps inform obstetrical care and testing. It also determines if a baby is growing normally and when to perform certain prenatal screenings. Babies born too small or too large for their gestational age are at risk of health problems.

Conception happens when sperm and an egg meet inside the fallopian tube or uterus. After fertilization, the embryo implants into the wall of the uterus, and a placenta forms. The embryo starts producing a hormone called human chorionic gonadotropin, or hCG, which can be detected in a person’s pee with at-home pregnancy tests. Most pregnancies end at around 40 weeks, from the time of conception.

Physicians estimate gestational age by adding 280 days, or 40 weeks, to the first day of a woman’s LMP. They do so as a simpler method than tracking the exact date of ovulation or fertilization, and because not everyone has a regular menstrual cycle. Fetal age can be measured using ultrasounds, which allows providers to see the size of a baby’s head, abdomen, and thigh bone. This can be a fun way to follow your pregnancy and watch the fetus grow week by week.

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During conception, sperm and an egg unite, creating a zygote. The zygote then moves down the fallopian tube and implants in the uterus. Implantation triggers the placenta to begin releasing hormones that help the baby grow. These hormones can also be detected in a woman’s pee by at-home pregnancy tests.

It can take hours or days for sperm and an egg to meet, fertilize, and implant. This is why pregnancy doesn’t always happen right after sexual activity.

Conception can occur throughout the month, but a person’s most fertile time is 5 days before and including the day of ovulation. For people with a 28-day menstrual cycle, this happens around day 14 of their cycles. Having sex during this time can increase the likelihood of getting pregnant.

Women who are trying to get pregnant may feel early pregnancy symptoms, such as spotting or increased vaginal discharge. However, these signs can be caused by other reasons besides pregnancy. For example, some women experience spotting and vaginal discharge during the first trimester before they ovulate, which is not a sign of pregnancy. A doctor can perform a blood test to confirm pregnancy. This test is more accurate than at-home tests because it measures lower levels of hCG in the body. However, it can be more expensive and take longer to receive results.