Fourth week of pregnancy: symptoms and pains, development of the embryo

In the fourth week, the tissues of the embryo begin to form, while the high levels of progesterone and hCG are responsible for most of the changes that occur in your body and the symptoms you may feel.

During the fourth week of pregnancy, the tissues of the embryo begin to form, while the high levels of progesterone and hCG are responsible for most of the changes that occur in your body and the symptoms you may feel.

At the 4th week of pregnancy a urine pregnancy test will almost certainly already be able to give correct results, because by now the production of beta hCG hormones is already well underway, and they can be found both in the blood and in the urine.

In this week the tissues of the embryo will begin to form: after implantation, the blastocyst divides into different cellular layers, which form the placenta and the embryo (which embryo will then become a fetus).

The embryo is composed of two layers called, one epiblast and the other hypoblast. The epiblast layer is divided into three “sheets” of essential cells:

  • the ectoderm (which will later give rise to the baby’s nervous system, skin, and hair);
  • the endoderm (which will then give rise to the gastrointestinal tract, pancreas, liver and thyroid);
  • the mesoderm (which will then give rise to the connective tissue, the skeleton, the circulatory system, the muscles and the genital-urinary system).

The hypoblast  contributes to the formation of the yolk sac and extraembryonic mesoderm .

Placental cells connect to the inner layer of the uterus, creating blood circulation to the growing embryo so that it can receive adequate nourishment and oxygen.

The trophoblast  (cellular tissue that serves to nourish the embryo) will begin to form the placental villi, thus initiating the uteroplacental circulation .

Therefore, it is from this moment that the connection between you and your future child begins: your blood will bathe the villi, and the nutritional exchange with the newly formed tissues will begin.

So let’s see what are the changes that take place in the woman’s body during the 4th week.

4th week of pregnancy: the woman’s body and the role of hormones

From this week on, the pregnancy hormone will increase exponentially (until it reaches its maximum between the 8th and 12th week.

You will probably already feel like “another person”: you will already feel that the baby is starting to grow inside you.

During the fourth week of pregnancy your volemia (blood volume) will start to increase, so that your baby can be supplied with enough blood.

During this time, your kidneys will have to work harder than usual because they have to “handle” a larger amount of blood, and this may lead to more frequent urination.

To be able to pump the additional blood, your heart   has to work harder, which can cause you to feel  tired and tired .

High levels of progesterone and hCG are responsible for most of the changes that occur in your body and the symptoms you may feel.

The embryo at 4 weeks of pregnancy

At this time, the embryo is still too small to be seen by ultrasound: it is the size of a poppy seed .

However, in some cases an ultrasound may already show a developing amniotic sac .

The sketches of the heart are already present – which had begun to form during the 3rd week [ 3 ] – even if it is still too early to hear its beat.

Pains and symptoms 4th week of pregnancy

During the fourth week of pregnancy, some women have a very light bleeding, called “implantation discharge”. These losses occur in the first 12 days of conception, and should not be confused with menstruation. They are also referred to as  spotting. They can be pink or brown in color.

As a result of all the changes (described in the previous paragraphs) that take place in your body, during the fourth week of pregnancy you will clearly begin to feel the first classic symptoms of an ongoing pregnancy.

In particular, in addition to the missed menstrual cycle (amenorrhea), you will begin to experience morning sickness, occasional dizziness, nausea and vomiting, a reduction in appetite.

At this stage you also have dizziness, bloating, bloating (caused by high progesterone levels), heartburn, headaches, breast tenderness , mood swings, constipation/diarrhea and cramps.

Other possible symptoms consist of,

  • lower abdominal pain;
  • lower back pain;
  • light vaginal discharge (caused by the implant);
  • shortness of breath;
  • food cravings or food cravings;
  • sensitivity to odors;
  • hot flashes.

Although it is, as a rule, still early to notice it, in this period some women are already starting to show a more swollen belly.

It’s too early to buy maternity clothes; you can rather try to use those clothes in your wardrobe that are more elastic and more comfortable.

In the following paragraphs we will try to answer some of the frequently asked questions relating to this period of pregnancy, and we will see what are the symptoms that could herald complications.

Other useful things to know about the 4th week of pregnancy

Beta hcg values ​​4 week

During the 4th week of pregnancy, thanks to a careful reading of the hCG levels (by specialized medical personnel), it will already be possible to have a first sign of the possibility of a twin pregnancy :

  • in a single gestation the average value of hCG, eighteen days after ovulation, is approximately 70mIU;
  • while it is about 200mIU in a twin gestation (these are values, however, which must be considered with great caution, as they can vary for various reasons and, therefore, are not 100% reliable).

However, for confirmation and more precise information, you should always refer to your doctor.

Nausea 4th week of pregnancy

Nausea is a rather annoying ailment. However, if it doesn’t lead to vomiting every time you eat or drink, don’t worry.

However, to avoid or reduce this nuisance it is useful,

  • eat smaller portions of food more frequently;
  • do long walks;
  • avoid foods that are too spicy or tasty. All of this should help you feel better.

Some studies claim that acupuncture is effective in combating nausea and vomiting in early pregnancy. But not all opinions agree. We therefore believe that further research is needed to be able to speak of scientific evidence.

Ginger intake also seems to have beneficial effects on the feeling of nausea.However, some experts warn that high doses of this herb could increase the risk of miscarriage. Although quantities of ginger less than 1500 mg are not considered dangerous, we advise you to consult your doctor before taking this root during pregnancy. 

There are also comfortable and safe anti-nausea bracelets, which you can buy online for a few tens of euros: these comfortable bracelets effectively affect the pressure points of traditional Chinese medicine by reducing/eliminating the sense of nausea.

Dental care

Bearing in mind that a dental infection, now but also later, could affect the development of the child or increase the risk of a premature birth, it is good that you start now to take special care of oral hygiene. You can eventually (if you don’t already have one) consider buying a new rotating electric toothbrush, and floss your teeth every day.


Check your weight systematically to keep track of how it will vary throughout your pregnancy.

Symptoms that may herald complications

While the symptoms listed above are normal, there are also some symptoms that could indicate the existence, or risk, of serious complications such as an ectopic pregnancy or miscarriage .

We indicate a few:

  • a dull pain in the lower abdomen (on both the left and right sides);
  • the fever;
  • vaginal bleeding;
  • vision disturbances.

In case you experience any of the above symptoms, consult your doctor first before drawing hasty conclusions.

4 weeks pregnant how many months is it?

If you are 4 weeks pregnant then you are in the first month of pregnancy. The birth is still about 8 months away.

Some tips for the 4th week of pregnancy

  • Evaluate whether you should be followed by an obstetrician during the next 36 weeks of gestation.
  • Make an appointment with a gynecologist to assess any risk of complications or congenital problems.
  • Follow a diet that is very rich in fruits and vegetables, and foods rich in folic acid
  • Your doctor may eventually recommend taking pregnancy-specific multivitamin supplements . In particular, starting this week, most women need to supplement the amount of folic acid normally taken with food. Women with a body mass index (BMI) over 30 in particular may need more folic acid.
  • Avoid smoking and  drinking alcohol .
  • If you haven’t already, tell your obstetrician or gynecologist about any medicines you are taking, or plan to take.
  • Keep fit: Regular exercise helps you better manage pregnancy-related weight gain, and it also has a positive effect on your mood.

Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.

She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform,

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