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How Long Does It Take for a Sperm to Fertilize an Egg?

2022-08-03T16:06:01-06:00August 3rd, 2022|

Pregnancy doesn’t happen right away after having sex. A lot needs to happen in order for sperm to actually reach an egg and for the fertilized egg to implant in the lining of the uterus.

Of course, having sex doesn’t mean you’ll get pregnant either, even if everything happens as it should. Here, we’ll look at how long it takes from when sperm are first released into the vagina to when you might see those pink lines on a pregnancy test. We’ll also discuss those first few signs and symptoms you might experience if you’re pregnant.

How long does fertilization take?

Fertilization can only happen if a sperm and an egg meet. Once it’s released from the ovary, an egg can only live for about 12 to 24 hours. Sperm, on the other hand, can live for 3 to 5 days inside your body.

There is a window of time known as the “fertile window” where pregnancy is possible during each month. An egg can be fertilized if you have sex anywhere from approximately five days before ovulation until the day of ovulation. The best chances of pregnancy are when sperm are present in the fallopian tube, ready to meet a just-ovulated egg.

What Happens During Fertilization?

Before sperm can fertilize an egg, they need to be “prepped” through a process known as capacitation. During capacitation, the sperm undergo changes from fluids in the female reproductive tract, which helps them to penetrate the egg.

Once they’ve reached the egg, multiple sperm can attach themselves and break through the outermost layer of the egg (corona radiata). Typically, only a single sperm can burrow through the egg’s second thicker layer (zona pellucida) contacting the egg’s inner membrane where fertilization takes place. A mechanism within the egg occurs to prevent any other sperm from entering or fertilizing the egg.

The egg begins to multiply and divide and over the course of 5 or 6 days, it becomes a cluster of 100-300 cells known as a blastocyst. It spends several days making its way to the uterus from the fallopian tube.

How long does implantation take?

Implantation is the process in which the blastocyst attaches to the uterine wall. It can take anywhere from 1 to 3 days after entry into the uterine cavity to completely implant. Implantation triggers the production of human chorionic gonadotropin (hCG), a hormone needed to support a pregnancy.

What Happens to Sperm Inside a Woman?

It’s a long journey through the vagina, cervix, uterus, and into the fallopian tubes, but very  few sperm actually make it to the egg. On average, there are 100 million sperm released during ejaculation, but that number drops to about 100-200 by the time they reach the egg.

The odds of getting pregnant

In one study of about 3,000 couples (ages 21-45) who received no direction on how to increase their chances of pregnancy, 58% became pregnant in six months. After one year, about 75% of them were pregnant.

When we break it down by month, at age 30, a healthy woman has approximately a 20% chance of getting pregnant each month. By age 40, that number drops to about 5%.

Can you improve your chances of getting pregnant?

Tracking your cycle and knowing when you’re ovulating is part of natural family planning and it can boost your chances of pregnancy every month, as well as avoiding it.

To get the most accurate picture of your fertility, it’s a good idea to use a combination of different methods to track when ovulation is occurring.

Basal body temperature

On average, body temperature rises slightly at the time of ovulation. Before ovulation, the average temperature is 96 to 98 degrees Fahrenheit, whereas after ovulation it rises to 97 to 99 degrees.

Using a basal thermometer, which is much more sensitive than a regular thermometer, you can track your temperature at the same time daily get an idea of when you ovulate. Most thermometers are used either in your mouth or rectum, with rectal temperature usually being more accurate. Tracking these temperatures on a chart or app on your phone can help you see a pattern over time and be able to predict when you ovulate. However, it only tells you you’ve already ovulated, not when you’re about to.

Cervical mucous tracking

This method tracks changes in consistency and amount of cervical mucus. Right before ovulation, cervical mucous increases in amount, and becomes thinner and more slippery, known as egg-white cervical mucus (EWCM). After ovulation, there is less mucous, and it becomes thicker. Having sex daily or every other day when EWCM mucous is present can increase your chances of pregnancy.

Ovulation predictor kit (OPK)

Despite the name, OPKs don’t actually predict ovulation in the sense that it can tell you when you’ve released an egg. These tests help detect surges, or rises, in luteinizing hormone, the hormone that triggers the egg to be released from the ovary. These tests are more challenging to use if you don’t have regular menstrual cycles. Still, research shows OPKs are generally reliable and help you learn about how your own cycle works.

When to take a pregnancy test

Since there is a range of 21 to 35 days for what’s considered a normal menstrual cycle, you will probably notice you’ll get your period 13 to 16 days after ovulation if you’re not pregnant. This is assuming you don’t have a health condition that can affect your cycle length, such as polycystic ovarian syndrome (PCOS).

After implantation, hCG is produced by the placenta and doubles in concentration every 2 to 3 days during the first few weeks in pregnancy. HCG can be detected in both blood and urine  tests. Some home pregnancy tests say they can detect hCG in urine as early as 10 days after implantation has occurred.

Early pregnancy signs

You may notice signs of pregnancy a few days after conception takes place, although this does vary from person-to-person. Early signs of pregnancy include:

  • Missing your period
  • Sore, tender breasts or nipples
  • Needing to use the bathroom more often
  • Feeling fatigued
  • Nausea, or “morning sickness”
  • Spotting
  • Food cravings or aversions
  • Headache

You may want to take a pregnancy test if you notice any of these signs occurring. Sometimes though, stress, hormone birth control, or fertility medications can mimic signs of pregnancy. Talk with your doctor if you aren’t sure you’re pregnant, or if you do get a positive home pregnancy test.

If you’re under 35 and have been actively trying to conceive for 12 months or more without success, make an appointment with a fertility doctor. If you’re over 35, wait only six months before getting help.

Contact us today to make an appointment with a CCRM Fertility specialist.

Written by: Dr. Katherine McKnight, a board certified reproductive endocrinology and infertility specialist at CCRM Fertility Houston

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