Pregnancy Week 4

What does my baby look like?

This week your embryo is about the size of a poppy seed. Even though it's still measured in millimeters, it's developing rapidly every day.

Your baby is protected by the fluid-filled amniotic sac and is connected to the yolk sac, which provides the support your baby needs in these early days.

The outer layer of cells will eventually become the placenta. The placenta will carry oxygen and nutrients to your baby and help remove waste products.

What's happening this week?

The fertilized egg has now implanted in the wall of your uterus. The embryo's cells are multiplying rapidly and beginning to separate into layers that will later become the different parts of your baby's body.

This is one of the most sensitive periods when it comes to factors that can affect your baby's development, which is why it's important to be mindful of safe habits.

It's also important to avoid overheating. High temperatures, especially in early pregnancy, have been linked to an increased risk of neural tube defects. For this reason, saunas, steam baths, and hot tubs are not recommended.

How many months pregnant am I?

This week you're in your first month of pregnancy. Pregnancy is measured from the first day of your last period, not from the day of conception. So even though conception happened about two weeks ago, this is officially considered week 4 of pregnancy.

What's happening at this stage?

• The fertilized egg implants into the inner lining of the uterus.
• The foundations of the biological bond between you and your baby are being laid.
• The cells divide into two main groups.
• One of these groups forms the embryo, and the other forms the placenta.

Your baby's developing cell layers

The embryo now has three distinct layers of cells. These layers lay the foundation for the organs and structures that will develop in the coming weeks.

• The inner layer, called the endoderm, will become the digestive system, liver, and lungs.
• The middle layer, called the mesoderm, contributes to the development of the heart, sex organs, bones, kidneys, and muscles.
• The outer layer, called the ectoderm, forms the nervous system, hair, eyes, and the outer layer of the skin.

The brain and nervous system that develop from these layers continue to form throughout pregnancy.

Calculating your due date

Your estimated due date is usually calculated as 40 weeks from the first day of your last period. Here's the confusing part: if birth happens on that date, your baby will have spent about 38 weeks in the womb. That's because the pregnancy count starts about two weeks before conception.

Your estimated due date is just an estimate. Pregnancy usually lasts between 37 and 42 weeks from the first day of your last period; most babies are born between 38 and 42 weeks, and it's common for first pregnancies to run a little late.

What's happening in my body?

You probably don't look pregnant yet. If this is your first pregnancy, you may not start to show until as late as week 12.

If you've been pregnant before, you may start to show sooner, since your uterus and abdominal muscles were stretched during your previous pregnancy.

You may get a positive pregnancy test this week

Many women don't feel anything at all this week. That's normal. Most early pregnancy symptoms usually become noticeable around week 6.

That said, some early signs can begin this week too:

• Breast tenderness can appear early. It usually starts between weeks 4 and 6 and may last throughout the first trimester.
• You may notice that your breasts are getting bigger or that your nipples are getting darker.
• Some women may see prominent blue or purple veins on their breasts.
• Rising progesterone levels can slow digestion, which may lead to gas and bloating.
• You may experience implantation cramps or light spotting.
• You may have mood swings.

Most cramps during pregnancy don't point to anything serious. However, if they're accompanied by bleeding, severe pain, or other noticeable symptoms, you should be evaluated for conditions like ectopic pregnancy or miscarriage.

Mood swings are also common in early pregnancy. Hormones, stress, and fatigue can all contribute. If your symptoms are severe or last longer than two weeks, talk to your doctor.

Pregnancy hormones kick in

About 6 to 12 days after conception, the pregnancy hormone human chorionic gonadotropin (hCG) begins to be produced. This hormone is what makes a pregnancy test turn positive.

hCG also stimulates the corpus luteum. The corpus luteum keeps producing progesterone and estrogen until the placenta takes over this job at around weeks 8 to 10.

Symptoms you might notice this week

At first you may not have any symptoms at all, and that's completely normal. Once the pregnancy hormone hCG starts to rise, some early symptoms may appear.

Symptoms you might experience in the first trimester include:

• a missed period,
• a metallic taste in your mouth,
• tender breasts,
• nausea,
• fatigue,
• new food cravings and aversions,
• a heightened sense of smell,
• needing to urinate more often,
• milky white vaginal discharge,
• light spotting,
• cramps similar to period pain,
• darkening or brown patches on your face,
• thicker and shinier hair,
• mood swings,
• bloating.

If you think you might be pregnant but aren't having any symptoms, you can still be pregnant. Shortly after conception, pregnancy is still at a very early stage and your body is preparing for the developing embryo. So having no symptoms at all isn't a bad sign on its own; everyone's pregnancy experience is different.

Bleeding or spotting – implantation bleeding

You may notice some very light bleeding or spotting. This is called implantation bleeding and may be related to the embryo settling into the wall of your uterus. This bleeding is usually very light; it can be light pink, light red, or light brown, and it may appear earlier than your expected period.

It's important not to mistake this bleeding for your period. You may also feel light, period-like cramps during this time.

Light spotting can happen in early pregnancy; however, if you notice bleeding at any stage of pregnancy, especially if it gets heavier or is accompanied by pain, it's important to contact your doctor. Bleeding during pregnancy isn't always a sign of a serious problem, but it does need to be checked.

Does a faint line mean you're pregnant?

Seeing a very faint line on a pregnancy test usually suggests that your pregnancy hormone levels are starting to rise. In that case, it can be helpful to repeat the test a few days later; a line that becomes clearer can indicate that the pregnancy is progressing.

If you have period-like bleeding after seeing a faint line on a pregnancy test, it may be a very early pregnancy loss, known as a chemical pregnancy. This is a sad situation; however, it doesn't rule out your chances of getting pregnant in the future on its own.

Keep taking your supplements, or start now

Eating a healthy, varied diet is important during pregnancy. Folic acid and vitamin D supplements are also important.

• Vitamin D supports the development of your baby's bones, teeth, kidneys, heart, and nervous system.
• Folic acid helps reduce the risk of neural tube defects in particular.

From the moment you find out you're pregnant, taking folic acid daily until week 12 is recommended. In some special cases a higher dose may be needed; that decision should be made by your doctor.

Talk to your doctor about your medications

If you're taking any medications, it's important to tell your doctor. Don't stop any medication suddenly without consulting your doctor. The goal is to create the safest treatment plan for both you and your baby.

If you have a pre-existing mental health condition and are taking medication for it, let your doctor and the specialist who manages your medication know about your pregnancy as soon as possible. Whether the medication is safe during pregnancy, or whether your treatment needs to be adjusted, should be assessed by a healthcare professional.

Avoid smoking, alcohol, and drugs during pregnancy

Smoking, secondhand smoke, alcohol, and illegal substances can lead to serious complications during pregnancy.

• Smoking can increase the risk of miscarriage, premature birth, and problems with your baby's development.
• There is no known safe level of alcohol during pregnancy.
• Illegal substances can seriously harm your baby.

If you used any of these before you realized you were pregnant, try not to blame yourself. If you're worried, talk to your doctor.

Schedule your prenatal appointment

If you've had a positive pregnancy test, call your doctor to schedule your first prenatal visit. Many providers schedule the first appointment around week 8. However, earlier evaluation may be needed in the following situations:

• vaginal bleeding,
• abdominal pain,
• severe nausea and vomiting,
• a known pre-existing medical condition,
• a history of a previous complicated pregnancy.

What is the first trimester like?

The first trimester can be tough for some women. Constant nausea, fatigue, breast tenderness, and a feeling of uncertainty are all common during this time.

This week your body begins to form the placenta and the amniotic sac. During this time:

• you may feel pressure or a slight sense of fullness in your abdomen,
• you may have breast tenderness,
• you may have light implantation bleeding.