Week 4 of Your Pregnancy

At four weeks pregnant, your fertilized egg will implant itself in your uterus. By the end of this week, you may even be able to get a positive pregnancy test!

Pregnancy Journey Week 4

Design By Alice Morgan / Illustration by Tara Anand

Week four of pregnancy is a very exciting time. Your fertilized egg will implant itself into your uterus and become an embryo. Once that happens, your body will get to work gestating and growing an embryo and (later) a fetus. By the end of this week, an at-home pregnancy test may even be able to detect your pregnancy.

Read on to learn what to expect when you're four weeks pregnant.

Pregnancy Week 4 Quick Facts

  • At four weeks, you're 1 month pregnant
  • You have 36 weeks until your due date
  • You're in the first trimester

Your Unborn Baby's Size at 4 Weeks

At the beginning of week four, implantation takes place. But before implantation occurs, a few other things have to happen. The whole process started only five to six days ago when your egg was fertilized by sperm. At that point, your fertilized egg became a zygote and underwent rapid cell division and multiplication. It also journeyed through the fallopian tube, where it reached the next stage of development—a blastocyst.

Once it reaches the uterus, it implants itself into the uterine lining. At this time, it's about 0.014 to 0.04 inches and less than 0.04 ounces. So tiny!

The blastocyst develops into layers of cells, some that will become an embryo and some that will become the placenta. An early amniotic sac is also developing. The placenta is what produces a hormone called human chorionic gonadotropin (hCG), which is what at-home pregnancy tests detect.

Pregnancy Symptoms Week 4

It's very early in your pregnancy, and you may not have many noticeable symptoms yet. In fact, many of the symptoms you may be experiencing will be similar to PMS symptoms. You won't know for sure if you are pregnant without taking a pregnancy test.

According to Orlando Santandreu, MD, chair of obstetrics and gynecology at Long Island Jewish Forest Hills in Queens, New York, some early pregnancy symptoms you might experience in week four include:

Early pregnancy symptoms are related to the circulating hormone hCG, says Dr. Santandreu. You may not be experiencing many symptoms yet because your hCG levels are just starting to increase when you're four weeks pregnant.

Still, everyone is different. Some people notice symptoms as early as week three depending on how sensitive they are to the hormone, Dr. Santandreu explains.

Spotting, light bleeding, or cramping during week four may be signs of implantation. According to the American College of Obstetricians and Gynecologists (ACOG), first-trimester bleeding occurs in 15-25% of pregnancies. Not all first-trimester bleeding is due to implantation—it could also be a sign of miscarriage or ectopic pregnancy, so it's always a good idea to contact a health care provider about bleeding during pregnancy.

If the cramping is intense and the bleeding is heavy, it's more likely that you are starting your period than that you are experiencing signs of implantation.

Developmental Milestones

During most of this week, your baby is referred to as a blastocyst. But by the end of week four—roughly 10 to 12 days after conception—it has reached a significant milestone: it will now officially be called an embryo.

In early embryonic development, the cells of the fetus form three main layers:

  • Inner layer: Forms the respiratory and digestive systems
  • Middle layer: Forms the heart, muscles, bones, and blood vessels
  • Outer layer: Becomes the brain, skin, and nervous system
pregnancy week by week week 4

Prenatal Tests and Doctor's Appointments

At four weeks pregnant, you will not see a health care provider for regular prenatal appointments. However, if by the end of this week, you get a positive pregnancy test, you can make your first appointment.

Most health care providers will have you schedule your first appointment for when you are eight to 10 weeks pregnant, though some will see you as early as six weeks depending on your medical history.

Even though you will not be seeing a health care provider just yet, you can call them with any questions or concerns. For example, if you have heavy bleeding or cramping after a positive pregnancy test, you shouldn't hesitate to reach out for help or advice.

Now is a good opportunity to jot down any non-urgent questions you have about your pregnancy and what to expect in the future. This way, you'll have a list available to ask during your first prenatal appointment.

Writing questions down beforehand can be helpful because it's easy to forget your questions when you are in the thick of an appointment. You might consider talking to your provider about any concerns you have about your symptoms, what pregnancy testing might be recommended for you, and thoughts about where you'd like to give birth.

Common Questions at This Pregnancy Stage

When is the earliest possible time you could get a positive pregnancy test?

"Today's pregnancy tests are quite sensitive," says Samir Hage, DO, an OB-GYN at Redlands Community Hospital in Redlands, California. Dr. Hage notes that some tests can turn positive as early as seven to 10 days after you conceive. "However, we do not recommend testing until after a missed period," he says.


How soon should you make a prenatal check-up appointment after you've gotten a positive pregnancy test?

If you don't have a history of ectopic pregnancies, early complications in prior pregnancies, or current medical conditions, you will not be seen this early in your pregnancy, even if you've gotten a positive pregnancy, says Dr. Hage. "Low-risk people should call and try to get an appointment around eight to 10 weeks," he explains. 


Not sure how far along you are? Fear not. "Most offices will help you determine how far along you are over the phone—and set up your appointments accordingly," Dr. Hage adds.


How do you manage the disappointment of a negative pregnancy test?

If you receive a negative pregnancy test—and were hoping for the opposite—you may be disappointed and discouraged. Pregnancy tests can elicit lots of emotions, depending on the situation and result.


But if you are feeling downtrodden, Shaghayegh DeNoble, MD, an OB-GYN and minimally invasive gynecologic surgeon at Advanced Gynecology in Wayne, New Jersey, suggests giving yourself time to heal and feel.


"The best way to manage the disappointment of a negative pregnancy test is to focus on self-care and allow yourself some time for sadness," Dr. DeNobe says. Consider focusing on the things that bring you joy and comfort, like reading, spending time with loved ones, or exercising. "It is also important to remember that a negative result does not mean that a person is unable to become pregnant in the future," she says.

Things You Might Consider This Week

The end of week four will be all about pregnancy testing. Waiting to find out if you're pregnant can be a time marked by both excitement and anxiety. You may have also received a positive result, which you weren't expecting. 

"With the individuals I work with, I see a wide variety of responses to the week leading up to a positive pregnancy test," says Jessica Lagrone, mom to three girls and certified doula and childbirth educator at Balanced Families. "Some are nervous and want to test as soon as possible, while others would rather wait until their missed period so they don't get a false negative result."

Lagrone says that she was personally too excited to wait. "I would buy a bunch of cheap pregnancy tests and take a test every morning for the few days leading up to the expected first day of my period," she shares. "When I was pregnant, the line would be faint and gradually grow bolder every day."

Of course, the downside to this testing approach was that in the months that Lagrone wasn't pregnant, she would be testing for multiple days in a row and experiencing heightened feelings of let-down and disappointment.

There's no one right approach when it comes to pregnancy testing in terms of how often to test. However, it is important that you take care of your mental health during this time and share any challenging feelings you may be experiencing with a trusted loved one.

Support You May Need This Week

Whether you got what you had hoped for or unexpectedly received a positive pregnancy test, it is common to experience some intense feelings right now—and not all of them will be joyful. Early pregnancy news comes with anxieties about your health, finances, job stress, and relationship worries.

Again, remember that these feelings are normal, but also know that it's healthy for you to share them. Consider sharing your feelings with a friend or family member; you may also consider contacting a mental health professional to help you process your feelings.

Head over to week five of pregnancy

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Sources
Parents uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Fetal development. National Library of Medicine. 2023.

  2. Changes during pregnancy. American College of Obstetricians and Gynecologists. 2023.

  3. Bleeding during pregnancy. American College of Obstetricians and Gynecologists. 2022.

  4. Getting to know the germ layers. Arizona State University. n.d.

  5. Schedule of prenatal care. UCLA Health. n.d.

  6. Pregnancy tests. Department of Health and Human Services: Office on Women's Health. 2021.

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