4 weeks pregnant is a milestone to celebrate and savor. You may have just had your first positive pregnancy test, or your period may have been late for a few days. Either way, you are officially about to embark on a beautiful journey that will last for nine months.
Your baby at week 4 of pregnancy
Some women claim to have a physical sensation of the fertilized egg snuggling down into the uterine lining. (The medical term for this is “implantation. There was a slight discomfort, like that experienced during ovulation. For at least another week, the rest of us will have no idea we’re expecting. Baby is busying herself while we are unaware.
The blastocyst implants itself in the uterine wall during week 4, at which point it begins to divide into cells that will become the placenta and cells that will become the baby. This week isn’t all about the Great Divide. The embryonic layers themselves begin to specialize in their own ways.
Baby’s hair, skin, eyes, and nervous system will develop from the outside layer; the heart, reproductive organs, bones, muscles, and kidneys will form from the middle layer; and the liver, lungs, and digestive system will form from the inner layer.
4 weeks pregnant is how many months?
When you are four weeks pregnant, you are officially in the first month of your pregnancy. Just another 8 months to go! Congratulations, you’ve already made great progress!
How big is your baby at 4 weeks pregnant?
By 4 weeks pregnant, your baby weighs about 0.01 ounces (0.3 grams) and measures about 0.4 inches (1 centimeter). The embryo is about 1/16th of an inch long, or 0.4 millimeters (mm). This means that if you were to put 100 embryos side by side on a ruler, none would be longer than 4 inches (10 centimeters) yet.
Fetal development in week 4 of pregnancy
During this week (week 4 of pregnancy), the unborn baby is 10,000 times larger than when he was conceived. To put that into perspective, he is the size of a blueberry or a little under a quarter inch from rump to head.
As a result of his rapid head growth, his head is now one-third of his overall size. Because most newborns are born with about 100 billion brain cells, called neurons, the brain must grow at about 250,000 neurons per minute during pregnancy.
Within the lining of the womb, the blastocyst grows and develops between weeks 4 and 5 of early pregnancy. As the outer cells reach out, they form links with the mother’s blood supply. They will eventually form the placenta (afterbirth). The inner group of cells will form the embryo. These inner cells form three layers at first.
These layers will develop into different parts of the body:
- inner layer (endoderm) – this layer will form the lungs, stomach, gut, and bladder, as well as the respiratory and digestive systems
- middle layer (mesoderm) – this layer will form the heart, blood vessels, muscles, and bones
- outer layer (ectoderm) – this layer will form brain and nervous system, the lenses of the eyes, the enamel of the teeth, and the skin and nails.
At this early stage, the embryo attaches itself to the yolk sac. The embryo receives nourishment from this sac. After a few weeks, the placenta will take over the transfer of nutrients to the embryo.
In the womb, placental cells grow deeply into the wall. They establish a rich blood supply here. As a result, the embryo receives all the oxygen and nutrients it needs.
Week 4 of Your Pregnancy
Week 4 is an important time in your pregnancy. This is when morning sickness usually starts, and your breasts may become enlarged and tender. If you haven’t started experiencing these symptoms yet, don’t worry – they usually begin during week 4 or 5.
If you’re feeling queasy, try eating small meals and snacks throughout the day instead of three large meals. A piece of toast and some crackers in the morning or a cup of yogurt with a banana are good options. And remember to drink plenty of water — at least eight 8-ounce glasses every day. This will help keep your body hydrated and stop dehydration from contributing to morning sickness.
Week 4 is also the time when your baby’s heart begins to beat. This is an amazing milestone in your pregnancy, and one that you’ll never forget. Your baby’s heart will continue to grow and develop throughout your pregnancy, and will eventually be able to pump blood around their little body.
If you’re feeling tired and exhausted, it’s normal. Your body is working hard to create a safe and healthy environment for your baby. Be sure to get plenty of rest, eat a nutritious diet, and drink plenty of fluids. If you’re having trouble sleeping, talk to your doctor – they may be able to recommend some safe sleep aids that can help you get the rest you need.
When to Worry
If you’re vomiting around the clock, you may have hyperemesis gravidarum. Be sure to let your doctor know if your morning sickness is keeping you from eating or drinking or impeding your everyday life.
Possible Pregnancy symptoms in week 4
The first trimester (0 to 14 weeks) of pregnancy is different for every woman, and every pregnancy. According to the Office on Women’s Health, one of the most common early signs is a missed menstrual period.
Common signs and symptoms of pregnancy
The most common early signs and symptoms of pregnancy might include:
- Missed period. A week without a menstrual cycle might indicate you are pregnant if you are in your childbearing years. If you have an irregular menstrual cycle, this symptom can be misleading.
- Tender, swollen breasts. In the early stages of pregnancy, hormonal changes can cause your breasts to become sensitive and sore. As your body adjusts to hormonal changes, the discomfort will likely decrease.
- Nausea with or without vomiting. In the first two months after becoming pregnant, you may experience morning sickness at any time of the day or night. There are, however, some women who feel nausea earlier and some who never do. The cause of nausea during pregnancy is unknown, but pregnancy hormones are likely to play a role.
- Increased urination. There is a possibility that you will need to urinate more frequently than usual. Pregnancy causes your body to produce more blood, which is processed by your kidneys and ends up in your bladder.
- Fatigue. Among the early symptoms of pregnancy, fatigue ranks high. There is no scientific explanation for why pregnant women feel sleepy during the first trimester. During early pregnancy, progesterone levels may rise rapidly, contributing to fatigue.
4 weeks pregnant belly size
Your belly is tiny at 4 weeks. It probably doesn’t even look like it could be growing anything but a few cells at this point. In fact, it’s more likely that the rest of your body has grown more than just the embryo itself! Even though it’s small, there are many changes happening inside that are preparing for life outside of you.
Most first-time pregnancies don’t show until around week 12. If you’ve had previous pregnancies you may show earlier as a result of stretching of the muscles in your uterus and belly.
4 weeks pregnant ultrasound
At 4 weeks, the blastocyst is dividing into an embryo and placenta, and an ultrasound of your uterus will only reveal what appears to be a tiny dot called the gestational sac; a pregnancy will not be seen until a later stage. Even with the most advanced transvaginal ultrasound equipment and the most skilled sonographer, your pregnancy must be at least five weeks along for it to be seen.
By locating the corpus luteum, the Ultrasound Care team can determine which ovarian has ovulated in the earliest stages of pregnancy. This allows us to determine which ovary has ovulated. This is a cyst that grows on the ovary and releases hormones to keep the uterine lining steady until the fetus can manufacture its own hormones. The lining of the uterus will be thick and colorful, reflecting changes caused by the hormones secreted by the ovary and your natural cycle.
Can you see a baby at 4 weeks on an ultrasound?
At four weeks pregnant, you probably won’t be able to see much of anything on an ultrasound. The baby is still very tiny at this point, and the ultrasound will likely just show a blur. However, your doctor may be able to tell if the pregnancy is progressing normally by looking at the size of the gestational sac.
Preparing for Pregnancy
To jumpstart a healthy pregnancy you might consider taking prenatal vitamins, drinking orange juice for folic acid, and getting some exercise. You may not even realize when you first become pregnant so refrain from drinking alcohol, taking drugs, or smoking cigarettes when you’re trying to conceive. Even prescriptions may be harmful to your developing baby, so be sure to speak to your doctor when you’re ready to start a family.
The importance of prenatal vitamins during pregnancy
During pregnancy, you need a greater amount of folic acid and iron. Why? Here are some reasons:
- Folic acid prevents neural tube defects. These defects affect the fetal brain and spinal cord in a significant way. Preferably, you should begin taking extra folic acid three months before you become pregnant.
- The placenta and fetus require iron to develop. The body uses iron to make blood to supply oxygen to the fetus. Additionally, iron helps prevent anemia, a condition in which the blood lacks healthy red blood cells
It’s important to consult your doctor to find out which are the best prenatal vitamins to take before pregnancy, and how to calculate your expected delivery date.
Can you get a positive pregnancy test at 4 weeks
Yes, you can get a positive pregnancy test at 4 weeks, but it is not very common. If you do get a positive test at 4 weeks, it is likely that the pregnancy hormone hCG has not yet reached its peak in your body and you may get a false positive result.
If you want to be sure of your result, it is best to wait until you are at least 6 weeks pregnant before taking a pregnancy test.
4 weeks pregnant hCG levels
At 4 weeks pregnant, your hCG levels can range from about 10 to 708 mIU/mL. This means that at this stage, your hCG levels can be quite variable. Nevertheless, it is still useful to know what the average level is for this stage of pregnancy.
One study found that the average hCG level at 4 weeks pregnant was 85 mIU/mL. However, it’s important to keep in mind that this number is just an average. Your hCG levels may be higher or lower than this and still be considered normal.
For some women, hCG levels may be as low as 25 mIU/mL, while for others they may be as high as 100 mIU/mL. It is important to remember that each woman is different and that there is no “normal” level of hCG. If you are concerned about your hCG levels, or if you are experiencing any other pregnancy symptoms, it is important to speak to your healthcare provider.
Can I be 4 weeks pregnant and still get a negative test?
Yes, It is possible to be four weeks pregnant and get a negative test. Getting a negative result doesn’t mean you’re not pregnant, it may just mean your hCG levels are not high enough for the test to detect the hormone in your urine. Even the most sensitive, ‘early detection’, pregnancy tests available can only detect pregnancy up to six days before your missed period (which is five days before you expect your period) and even then, these tests won’t be able to detect every pregnancy that early.
Explore more in your pregnancy week-by-week
Follow your pregnancy week-by-week to find out how your baby is growing and what is happening to your body.
First Trimester Weeks:
Second Trimester Weeks
Third Trimester Weeks
Pregnant Women Also Asked:
Got questions about week 6? Other ladies have wondered this…
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- Human chorionic gonadotropin hormone (HCG). (2018.)
- Knowing if you are pregnant. (2019).
- Navigating your pregnancy. (n.d.).
- Pregnancy. (2017).
- Pregnancy: Sensitivity and specificity. (n. d.).
- Pregnancy tests. (n.d.)
- Pregnancy week by week. Weeks 1–2. (n.d.).
- Stages of pregnancy. (n.d.).