How long does it take for sperm to reach the egg?

Whether you’re trying to get pregnant, wanting to prevent pregnancy, or just looking for a deeper understanding of the biological process of fertilization, you may be asking yourself questions like “how long does it take for sperm to reach the egg?” and, “how fast does sperm travel?” In this article, we’ll answer these questions and more, so that you can use this knowledge while planning or preventing pregnancy.

How does sperm reach the egg after sex?

Many biological processes need to happen on the path to pregnancy. One that you were probably taught in sex ed is that sperm needs to fertilize an egg. While this is true on a basic level, the whole process is a bit more complicated than that.

Before we explore the timing of fertilization, let’s first go over how sperm enters the female reproductive system and reaches the egg after sex. First, if ejaculation happens during unprotected intercourse, sperm cells enter the vagina via semen [1, 2]. 

Most of the time, the pH of the vagina is quite low to protect against sexually transmitted infections. After sex, it increases suddenly to create an environment that is favorable to the transportation of sperm [3]. 

The sperm cells then begin the journey of finding an egg cell to fertilize. Egg cells develop in the ovaries, and most commonly just one egg cell is released into a fallopian tube each cycle during a process called ovulation. Keep in mind that if you’re on certain types of hormonal birth control, ovulation is suspended and no egg cell is released [1, 2].

In order to reach the egg cell in the fallopian tube, sperm must first pass through the cervix — a small opening that is blocked by cervical mucus for most of the menstrual cycle, except around ovulation [2]. Many sperm don’t make it through the cervix, but those that do enter the uterus. 

The two fallopian tubes are accessible from the uterus, but there is usually only a single ovulated egg in one of the tubes. This means that any sperm that enter the empty fallopian tube are at the end of their journey at this point. In fact, most sperm cells don’t survive this initial journey through the female reproductive system. Unsuccessful sperm cells are removed by white blood cells in the female body [4].

How long does it take for sperm to reach the egg?

That process — from ejaculation in the vagina through the cervix and uterus and finally into the fallopian tubes  — can take just a few minutes to a few hours after sex depending on a number of factors, including sperm’s motility (their ability to move, or “swim” as people often say) [3].

But after this initial journey, sperm cells need to be modified within the fallopian tubes through a process called capacitation. It can take up to 6 hours, and in that time, sperm cells attach to the lining of the fallopian tubes where their membranes are modified and their motility is increased, giving them a better chance at fertilization. Once they’re capacitated, sperm detach from that lining and progress through the fallopian tube via a combination of their own motility, rhythmic contractions of the muscles in the tube’s wall, and a flow of tubal fluids. This shows that successful sperm transport through the female reproductive tract depends on both the sperm’s capabilities and the female body’s efforts to facilitate that movement [4, 5].

After capacitation, sperm can then live for up to five days in the fallopian tubes. This means that if you have sex five days before ovulation, it’s possible for sperm to travel to the fallopian tubes and stay there until the egg cell is released a few days later [4]. 

Unlike sperm cells, once the egg is released, it only lives for about 12 to 24 hours, which is when fertilization can happen [2]. This means that this period of about four to five days before ovulation to the day of ovulation is your fertile window, and pregnancy is only possible if the timing of sex lines up with this window [4].

How many sperm reach the egg?

Out of the millions of sperm cells released during ejaculation, only a few hundred will reach the site of fertilization in the fallopian tube. While that’s a huge drop, only one sperm cell is needed to successfully fertilize the egg cell, and this is often a random selection from that few hundred that reached the tube [5]. Learn more about sperm count here.

How does sperm fertilize the egg?

Once the sperm cell reaches the egg, the process of fertilization begins. First, the sperm must migrate through a layer of follicle cells that surround the egg cell before binding to and crossing through the egg’s outer coating. That outer coating becomes impenetrable by other sperm once one has entered. Then, the sperm must bind to and fuse with the egg’s plasma membrane to successfully complete the fertilization process [5].

How long does it take a fertilized egg to implant?

Implantation is when the fertilized egg travels to the uterus and implants into the uterine lining., and the process of implantation can take several days or even a few weeks to complete [6].

Can you feel the fertilization or implantation of the egg?

You won’t feel fertilization or implantation happening, but there may be signs of these early pregnancy processes. One sign is implantation bleeding. It may sound intense, but it’s actually just harmless, light spotting that might happen when the fertilized egg implants into the uterine wall. This action can break down some blood vessels in the area, which leads to light bleeding and potentially some implantation cramps as well [7, 8]. 

About one third of pregnant women experience early pregnancy bleeding, and it’s usually not cause for concern (although it may be commonly confused with a light period if you don’t know that you’re pregnant) [8]. If you’re ever unsure or concerned about what’s happening in your body, consult your healthcare provider for more information and care.

How can you prevent sperm from reaching and fertilizing the egg after unprotected sex?

If you want to prevent pregnancy and all of the biological processes above after unprotected sex, emergency contraception can help. The sooner you use emergency birth control, the more effective it is. There are two types: the copper IUD and the emergency contraceptive pill [10].

The copper coil IUD is generally more effective, and it’s also a non-hormonal birth control method that can be used for up to 10 years once inserted. The copper IUD starts working to prevent pregnancy as soon as it’s placed into the uterus, and it does this by preventing implantation. It’s also toxic to sperm. This means that it can be placed up to 5 days after sex (before the fertilized egg reaches the uterus) [10]. 

The emergency contraceptive pill is also known as the morning after pill or by common brand names Plan B, Levonelle, or ellaOne. It prevents pregnancy by inhibiting ovulation, so it won’t be effective if you’ve already ovulated [10].

What can you do to increase the odds of getting pregnant?

Alternatively, if you’re trying for a baby, there are many different factors that affect how long it takes to get pregnant. But overall, the best way to increase your odds of fertilization and implantation is to time intercourse within your fertile window each month. If you’d like support in identifying your fertile window, NC° Plan Pregnancy may be a helpful tool. It uses a scientifically-backed algorithm to analyze your temperature and fertility data and predict ovulation and the most likely time to conceive. Research shows that couples using Natural Cycles to get pregnant conceive in three cycles on average [11].

Plan or prevent pregnancy with Natural Cycles

Thanks for reading up on the fertility journey. Understanding the process of fertilization can help you make informed decisions about your fertility. Whether you’re trying to conceive or trying to prevent pregnancy, identifying your fertile window is key. See if Natural Cycles’ personalized predictions and recommendations can support your goals today.