4. WOP

In the 4th week of pregnancy, the time has finally come – you are “officially” pregnant. The embryo is still tiny in the 4th week.

Find out here whether you can already recognize something on the ultrasound image and what is particularly important now.

This happens with you

In the 4th week of pregnancy, the embryo – as your baby is called in the first 3 months – is about the size of poppy seeds. The fertilized egg has settled in your uterus. From this point on, the little embryo will grow bigger and bigger every day.

Important facts about the 4th WOP: What you should know

A lot will change in your body during the 4th week of pregnancy. The fertilized egg has successfully implanted in your uterus. The embryo is now about the size of poppy seeds.

Now you should pay attention to a healthy lifestyle, so that you can support your body optimally during pregnancy. A healthy diet, light exercise and abstaining from alcohol and nicotine are especially important now.

Since the so-called all-or-nothing principle prevails in the 4th WOP, a miscarriage can occur during this time under certain circumstances. Unfortunately, the first weeks of pregnancy are always particularly delicate.

Our tip: Take care of yourself and your body and enjoy the exciting time ahead.

Tip for fathers-to-be:

Pregnancy test – while some expectant fathers want to be present at the test, some prefer to be surprised. Talk to your wife about it and decide together how you want to be sure about the pregnancy

How your body changes in the 4th week of pregnancy

Due to the increased release of corpus luteum hormones, you may experience the first pregnancy symptoms in the 4th week of pregnancy. Since the embryo now needs special protection, all functions in your body run a little slower than usual.

During the 4th week of pregnancy, you may feel tired and listless. Constipation or other intestinal problems may also occur.

After the embryo has settled in the lining of the uterus, theplacenta takes over the production of the corpus luteum hormone.

This also causes the familiar pregnancy symptoms, such as nausea or fluctuations in sensation. You may feel a slight tightening in your breasts. Abdominal pain or back pain can also occur from the 4th week of pregnancy. You can counteract these complaints with massages, warming baths and sufficient relaxation.

Signs of pregnancy in the 4th week of pregnancy

Now an exciting time begins: From now on you can notice the first signs of pregnancy on your body. We have summarized all the symptoms for you at a glance.

Urinary urgency

Due to the increase in hormones, you may feel a stronger urge to urinate than usual. The hormone progesterone promotes the relaxation of the uterine muscles.

Over the next nine months of your pregnancy, your uterus will expand to make room for your baby. Unfortunately, the muscles of the bladder are also affected.


It is not uncommon to experience light spotting – called implantation bleeding – during the 4th SSW. This is completely normal.

If the bleeding becomes heavier or lasts more than two days, it is probably just your period. If you have already had a positive pregnancy test or are worried, you can ask your gynecologist for advice.

Mood swings

Pregnancy hormones can really mess with your emotions. This is a good time to try out some methods that will relax you. Massages, enough sleep and the right diet will help.

The breasts are tense

The hormonal change causes your breasts to adjust to milk production. The growth of the mammary glands is stimulated and the color and shape of the nipples can also change.

Morning sickness

In the 4th week of pregnancy you may suffer from morning sickness. Nausea is probably the best-known pregnancy symptom and is experienced differently from woman to woman. Most often, however, nausea occurs in pregnant women in the morning.

While some expectant mothers only feel slightly unwell, others have to throw up every day. The good news: the frequency of morning sickness usually decreases from the second trimester of your pregnancy.

Light discharge

During the 4th week of pregnancy, an odorless discharge is a normal symptom. The color varies from clear to milky. If you notice any unusual discharge, you should tell your gynecologist.


Do you often feel exhausted during the day? Your body is going through many changes now. It first has to get used to the new state – this can take some time. This change naturally affects your energy balance. However, iron deficiency

can also be a reason for the state of exhaustion.

Did you know? More than 20% of women in Europe suffer from iron deficiency during their pregnancy. Talk to your gynecologist about taking additional iron to prevent deficiency symptoms.

How safe is a pregnancy test in the 4th week of pregnancy?

Many expectant mothers have become aware of a possible pregnancy in the 4th week of pregnancy due to an early menstrual period – or implantation ble eding. You can determine the hCG level in your urine by means of an early test. In the 4th week of pregnancy, the hCG level is usually high enough for a test to be positive if you are really pregnant.

But it is also possible that the pregnancy hormone has not yet been sufficiently formed and the test is negative despite the existing pregnancy.

To be on the safe side, you can have a blood test performed by your doctor at the end of the 4th week of pregnancy. A pregnancy can thus be detected almost 100%.

Which pregnancy test is the best?

Pregnancy tests are available in many different versions. In addition to the specified precision, they also differ in the display and the duration of the analysis. If you are unsure about “line tests”, a pregnancy test with a written display is recommended.

Early test

An early test gives you very early information about an existing pregnancy. Early tests detect an hCG concentration in your urine after only 8 to 10 days. The concentration of hCG is highest in the morning – so test your urine for the pregnancy hormone in the morning.

Digital test

Digital tests also show the week you are in, among other things. They can also be used a few days before your missed period and are extremely accurate in determining whether or not you are pregnant.

Medical examination

The most accurate method is to visit a gynecologist. He or she can confirm whether a pregnancy is present or not already in the first days of pregnancy.

4. WOP (3+0): What does that actually mean?

You have probably read that women indicate the duration of their pregnancy as follows: WOP 4 (3+0). But what does that mean exactly?

The 4th WOP means that you are three weeks and x (the days are counted from 0 to 6 for the individual days of the week) days pregnant. We will enlighten you with a small calculation example.

3+0 = day 1 of the 4th WOP

3+1 = day 2 of the 4th WOP

3+2 = day 3 of the 4th WOP

3+3 = day 4 of the 4th WOP

3+4 = day 5 of the 4th WOP

3+5 = day 6 of the 4th WOP

3+6 = day 7 of the 4th WOP

The crucial 4th WOP: The all-or-nothing principle

Not only in the 4th week of gestation, but also in the first 3 weeks, many external influences play an important role in ensuring that implantation is successful.

The following factors can be responsible for preventing the implantation of the fertilized single cell:

  • Deficiency of the corpus luteum hormone
  • Too much stress
  • Alcohol and nicotine
  • Unhealthy diet

Even if a fertilized egg has been able to implant, other complications can occur. For example, the embryo may be rejected by your body (miscarriage) or there may be deformities during development.

In the 4th week of pregnancy, you should therefore do everything you can to support your body as much as possible during the pregnancy. How you can best do this, you will learn in the further course of this article.

In summary, the all-or-nothing principle prevails in the 4th week of gestation. If the embryo is damaged in any way, or if implantation does not work, your body will reject the egg. If everything works smoothly, the embryo will continue to develop.

What can be seen on the ultrasound during the 4th week of pregnancy?

Expectant parents are full of anticipation for the first ultrasound

and can hardly wait to see their own baby for the first time. But can the embryo really be seen on the ultrasound in the 4th week of gestation?

The good news is that you can already see something in the 4th week of pregnancy. However, “only” the amniotic cavity. The embryo is still much too small. In the 4th WOP it is about 0.5 mm in size.

Only in the course of the pregnancy will you be able to see the little miracle in your belly more and more clearly on the ultrasound. From around the 7th week of pregnancy, the embryo is clearly visible on the ultrasound image.

How important is an ultrasound in the 4th week of pregnancy?

Since implantation has not occurred until the 4th WOP, an ultrasound is not usually performed at this time. A blood test or urine test provides more clarity.

Instead of performing an ultrasound in the 4th week of pregnancy, three ultrasound examinations are usually scheduled during the rest of the pregnancy.

Various measurements are taken to see how your baby is developing and to check how it is progressing.

Ultrasound examinations

The first ultrasound examination usually takes place between the 9th and 12th week of pregnancy. The crown-rump length, the biparietal diameter and the diameter of the amniotic sac are measured.

The second ultrasound examination is scheduled between the 19th and 22nd week. The size of your baby will be measured. Furthermore, the position of the placenta and the amount of amniotic fluid are checked. Your baby’s heartbeat and movement pattern will also be closely examined.

The last ultrasound examination is scheduled between the 29th and 32nd week of pregnancy. Your gynecologist will check the position of your baby and its size. The function of the organs and the amount of amniotic fluid will be checked again.

What happens to the baby

The fertilization of the egg

The mature egg was already fertilized in the 3rd week of pregnancy and was on its way to your uterus. At this point, the embryo already carries your genes and those of your partner.

The uterine lining was already produced in the 2nd week and provides important nutrients for the optimal development of the embryo.

The corpus luteum hormone plays a decisive role in this development. This is produced by your body at the beginning of pregnancy.

The implantation

The little embryo has arrived on its journey and is in your uterus. But before it can implant in your uterine lining, it must first shed its shell.

A small amniotic fluid cavity and a yolk sac develop, which ensures the supply of nutrients. The embryo is now surrounded by the vital placenta, also known as the placenta, which is discharged as afterbirth during delivery.

The cells from which the embryo is formed are called the “germinal shell”. All the important organs will later develop from this. Which functions they will later take over is already clear in the 4th WOP.

Your baby will nest in your uterus at the beginning of the 4th week of pregnancy. But before implantation takes place, the embryo has to come out of its egg shell. The embryo penetrates the mucous membrane of the uterus in order to continue its care.

The little embryo now needs your nutrients and oxygen to continue developing. Please make sure to abstain from alcohol and nicotine immediately.

Your baby is about the size of a poppy seed or the size of a dot that you draw with a pencil

This is important now

Here’s how you can support your body in the 4th week of pregnancy

In the 4th week of pregnancy, your body is busy supplying the embryo with important nutrients. This section explains what you can do to support your body during this exciting time.

The right diet

You’ve probably heard the phrase “eating for two” before.

It doesn’t necessarily mean that you should eat twice as much. It’s more about what you eat. Are you wondering which foods are particularly nutritious? We will tell you. Basically, you should always keep in mind that everything you eat also reaches your child. Things that are unhealthy for you are in most cases not beneficial for the development of your child.


Eggs contain a lot of proteins and valuable D and B12 vitamins. In addition, you can prepare them quickly and easily – this is great for everyday life.

Dairy products

Milk, cheese and yogurt are rich in calcium. Calcium is the most important bone building block – almost 100% of the calcium in the body is bound in the bone.

When there is a deficiency of calcium in the blood, it is released from the bones, which can affect bone strength.

Attention: You can consume heat-treated milk without any problems. You should avoid raw milk.

Since raw milk and raw milk products are not heated, they may contain pathogens such as listeria. These are killed when milk is heated.


Nuts are the ideal on-the-go snack. They are rich in proteins and healthy fats that support your baby’s development.


Fruit contains many vitamins and fiber – important components of the diet during your pregnancy. Fruit can work wonders for constipation during pregnancy.


Light exercise can, for example, reduce back pain or dizzy spells. It also gets your circulation going again. However, the first weeks of pregnancy are considered particularly delicate.

Therefore: Take care of yourself and your body. However, light sports such as yoga or swimming are okay. To be on the safe side, you should talk to your doctor about it.

Folic acid

Foods containing folic acid are particularly important during pregnancy. Why is that? The intake of folic acid during pregnancy ensures the development of the embryo’s brain and nervous system.

The recommended daily intake for men and women (outside pregnancy and lactation) is 300 mg of folic acid.

Pregnancy increases the need for folic acid, so 550 mg per day is recommended during this time. When you are breastfeeding, you need about 450 mg per day.

Folic acid is found in the following foods:

  • Cabbage
  • Leaf spinach
  • Salads
  • Tomatoes
  • Fruits (e.g. oranges)
  • Whole grain products
  • Legumes
  • Nuts
  • Sprouts
  • Wheat and soy germs
  • Dairy products

However, it is usually not enough to cover the need for folic acid through food. Doctors and midwives therefore recommend taking folic acid supplements. It is best to talk to your doctor about this.


Everyone needs magnesium. Magnesium is a vital mineral that we need to take in regularly through food.

It performs numerous tasks in the human body. For example, it stabilizes the bones and contributes to the function of heart and vascular muscle cells.

However, pregnant women usually take in enough magnesium through a balanced diet. In the case of pregnancy complaints, such as calf cramps, premature labor or preeclampsia (pregnancy poisoning), the additional intake of magnesium supplements makes sense. You should also discuss this with your doctor,

Midwife tip

The first weeks of pregnancy are particularly delicate. Now it is important to support your body as much as possible during pregnancy. You can do this by eating a healthy diet, avoiding stress and abstaining from alcohol and nicotine.

Since you now know how important folic acid is for the development of the embryo, I advise you to take folic acid supplements.


What happens in the 4th week of pregnancy?

In the 4th week of pregnancy, the fertilised egg nests in your uterus. From now on, the embryo is supplied with all the nutrients you consume.

What can you see in the ultrasound during the 4th week of pregnancy?

Even if the anticipation is enormous – in the 4th week of pregnancy only the amniotic cavity can be seen on the ultrasound. It is not until the 7th week that the small embryo can be seen on the ultrasound.

How safe is pregnancy in the 4th week of pregnancy?

The first weeks of pregnancy are considered particularly delicate. During this time, external influences can cause your body to reject the embryo. However, with a healthy lifestyle you can optimally support your body during pregnancy.

4th WOP: Bleeding like period?

Light bleeding is caused by implantation in the uterus, also called implantation bleeding. If the bleeding is persistent, there may have been complications with implantation and the fertilised egg may have been rejected – in the form of the normal recurrent period. Consult a doctor for certainty.

Video about the 4th WOP

Want to know the signs of pregnancy in the 4th week of pregnancy? Crystal reveals it to you.

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