Week 4 of Your Pregnancy

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.

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. This is a process that started five to six days ago when your egg was fertilized by sperm. At that point, your fertilized egg became a zygote, and underwent a rapid period of cell division and multiplication. It also made its journey through the fallopian tube and into the uterus.

Once your egg implants itself into the uterine lining, it reaches the next stage of development and becomes a blastocyst. 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 be able to know for sure if you are pregnant without taking a pregnancy test.

According to Orlando Santandreu, M.D., 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:

An aversion to certain foods
Increased fatigue
Breast tenderness or enlargement with sensitivity
Changes in sleep patterns
Changes in the sense of smell
Mild cramping and or spotting

Early pregnancy symptoms are related to the circulating hormone HCG, says Dr. Santandreu. Part of the reason that you may not be experiencing many symptoms yet is because your HCG levels are just starting to increase in your fourth week. Still, everyone is different. "Some patients are able to have symptoms as early as the first week in their pregnancy [or week three, the week of conception] depending on how sensitive they are to the hormone," Dr. Santandreu explains.

Spotting, light bleeding, or cramping during week four may be a sign of implantation bleeding, which affects about 25% of pregnant people and is caused by the implantation of the fertilized egg into the uterine lining. 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 implantation bleeding.

If you are unsure about symptoms like bleeding, cramping, or any other concerning body changes, please reach out to an OB-GYN, midwife, or other medical professional who can help you understand what is happening and what steps need to be taken.

Developmental Milestones

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

In early embryonic development, the cells of the fetus form three main layers: an inner layer forms the respiratory and digestive systems; a middle layer forms the heart, muscles, bones, and blood vessels; and the outer layer becomes the brain, skin, and nervous system.

Prenatal Tests and Doctor's Appointments

At four weeks pregnant, you will not yet be seeing a medical 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 OB-GYNs, midwives, and other medical professionals 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.

Even though you will not be seeing a medical 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 start 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 down questions beforehand can be helpful because it's easy to forget your questions when you are in the thick of an appointment. Questions you might consider asking your provider may include concerns 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, D.O., an OB-GYN at Redlands Community Hospital in Redlands, California. Some tests can turn positive as early as seven to 10 days after you conceive, Dr. Hage notes. "However, we do not recommend testing until after a missed period," he suggests.

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 to manage the disappointment of a negative pregnancy test?

If you receive a negative pregnancy test—and were hoping for the opposite result—you may be disappointed and discouraged. Pregnancy tests can elicit various emotions, depending on the situation and result. But if you are feeling downtrodden, Shaghayegh DeNoble, MD, OB-GYN, and minimally invasive gynecologic surgeon at Advanced Gynecology in New Jersey, 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 reminds.

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 that they don't get a false negative result, Langrone describes.

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. But 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, concerns about finances, job stresses, and relationship worries.

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

Head over to week five of pregnancy