The early days and weeks of pregnancy are the start of an exciting journey, but at this stage you may not even suspect you are pregnant! Although at one, two, or three weeks pregnant you may not notice any very early signs of pregnancy, there’s a lot happening on the inside. Read on to learn more about what’s going on inside your belly, the symptoms of pregnancy in weeks one to three, how to calculate your due date, and more.

What Will Happen in Your Belly in the First Three Weeks of Pregnancy

If you have a typical 28-day menstrual cycle, one of your ovaries will release an egg around 14 days after the first day of your last period. The egg will travel down one of the fallopian tubes where it may be united with sperm.

It’s worth noting that sperm can live inside your body for up to five days, and your egg has a lifespan of up to one day. This means your window of fertility is about five days before you ovulate to one day after. Read on to find out what happens from before conception and onward.

1 Week Pregnant

Your journey through pregnancy starts now, but did you know you’re not technically pregnant yet? Healthcare providers calculate the length of a pregnancy as 40 weeks from the first date of your last menstrual period, and, as we mentioned above, ovulation (and possibly conception) happens about 14 days after the start of your period, assuming you have a 28-day cycle. So, for the sake of calculation, this week and the next are considered part of your pregnancy, even though you haven’t conceived just yet. It can be mindboggling, but at one week pregnant, you’re actually not!

2 Weeks Pregnant

At two weeks pregnant, so to speak, your period may be over and ovulation may be just days away. At the end of this week, if you have sex, egg and sperm can meet and conception can take place. If this does happen, your uterus is about to become a very busy place!

3 Weeks Pregnant

By three weeks pregnant, your belly will be a hive of activity—even though you may not be able to tell. If the sperm and egg find each other, they’ll join up in a fallopian tube to create a single cell called a zygote in a process called fertilization. This zygote carries chromosomes from the mother and father, and sets the first building blogs of your future baby’s genetic makeup. The zygote then gets moving down the fallopian tube, toward the uterus, as it starts dividing into a larger group of cells.

Early Pregnancy Symptoms: First Signs You Might Be Pregnant

During weeks one, two, or three, you may not even suspect you’re pregnant and you might not notice any pregnancy symptoms at all. It’s still very early. Typically, missing a period will be the first clue that you may be pregnant, and around the time you miss a period—or a little later—you may start noticing other pregnancy symptoms. Of course, some women sense some subtle changes early on and recognize them as signs of pregnancy right away. One early pregnancy symptom can be implantation bleeding, which is some light spotting that occurs when the tiny ball of cells (now known not as a zygote, but as a blastocyst) attaches to the uterine lining. This light bleeding is normal, and can sometimes be mistaken for menstrual blood. Other signs of pregnancy in the first month can include bloating, gas, fatigue, breast tenderness, moodiness, and frequent urination. Morning sickness is another common symptom of early pregnancy, but it usually crops up between weeks four and nine.

When Will You Be Able to Confirm That You’re Pregnant?

If your period is fairly regular, your first clue that you may be pregnant could be that your period doesn’t come on time. If you think you might be pregnant, take a home pregnancy test. These tests can confirm a pregnancy by checking for a pregnancy hormone called hCG in urine. Keep in mind, if you take the test too early there may not be enough of the hormone in your urine yet for the test to be accurate. Check the packaging on the test you buy for information on when to take the test. Some require you to wait until at least the first day of your missed period. Others can detect lower levels of hCG, and may be accurate a little earlier on. If you think you may be pregnant but the test says otherwise, try again after a few more days or speak to your healthcare provider. You can also ask your healthcare provider to confirm your pregnancy. Your provider will do a blood test.

When Will Your Baby Be Born?

When you find out you’re pregnant, one of your first questions might be “when will I get to meet my baby?” For an estimate, try our Due Date Calculator, where you can simply enter the first day of your last period or the date of conception. Keep in mind, only about 5 percent of babies are born exactly on their due date. It’s totally normal to give birth in the two weeks either side of your due date. Your healthcare provider can also give you an estimate of when your little one will be born. Due dates are typically calculated as 280 days, or 40 weeks, from the first day of your last menstrual period. When calculating a due date and the weeks of pregnancy in this way, the first week of pregnancy is actually the week you had your period, and were not pregnant yet. It’s hard to wrap your head around but, based on how due dates are calculated, you are not actually pregnant yet in the first couple of weeks of the 40 weeks of pregnancy.

How Far Along Am I?

Knowing how far along you are in pregnancy is useful for both you and your healthcare provider. Your provider will use this information to check on your baby’s growth and development, to keep an eye on your health, and to schedule tests and exams. The weeks of pregnancy are also grouped into three trimesters: First trimester: 0 to 13 weeks (roughly months one to three) • Second trimester: 14 to 27 weeks (months four to seven) • Third trimester: 28 to 40 weeks (months seven to nine) So that you can see at a glance how far along you are in your pregnancy, and which trimester you are in, check out the illustration below:

How far along am I


What Precautions Should You Take if You’re Trying to Conceive and During Early Pregnancy?

If you’re trying to get pregnant, you might need to make some healthy lifestyle changes. Since you won’t necessarily know you are pregnant during the first few weeks, it’s best to take some precautions as soon as you start trying to conceive and then continue with them during your pregnancy. Make sure you’re eating healthily and getting regular exercise. Your healthcare provider may also recommend you start taking folic acid when you start trying for a baby. Folic acid is a B vitamin that helps reduce the risk of certain birth defects that affect the baby’s brain and spine. Your healthcare provider will be able to recommend a prenatal vitamin that contains the 400 micrograms of folic acid needed. Pre-pregnancy is also a great time to eliminate some less healthy habits. Quit smoking and drinking alcohol. Some healthcare providers may advise you to limit your caffeine intake, too. Secondhand smoke can be harmful to you and your baby, so if your partner is a smoker, it’s best if he or she quits, too.

The Big Picture

Outwardly, it might seem like there’s not much going on during weeks one, two and three of pregnancy, but this is an eventful time for you and your growing family. Inside, a flurry of activity is taking place and by the end of these first few weeks the first building blocks of your baby will be in place. Perhaps even unbeknownst to you, you’re at the start of a wonderful journey. If you’re interested in what happens in the remaining weeks of pregnancy, sign up below and we’ll send updates to your inbox:

How we wrote this article
The information in this article is based on the expert advice found in trusted medical and government sources, such as the American Academy of Pediatrics and the American College of Obstetricians and Gynecologists. The content on this page should not replace professional medical advice. Always consult medical professionals for full diagnosis and treatment.