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

In the absence of the classic symptoms, by the third week of pregnancy most women do not know they are pregnant. However some simple signs may show up. Let’s find out more.

For the reasons explained in the previous article on the first two weeks of pregnancy , technically you are not pregnant until the first few days of the third week of pregnancy, when ovulation and conception occurs. Precisely at the source of these important events, it is with the 3rd week of pregnancy that the very first symptoms of the pregnancy in progress could begin to appear. However, remember that these symptoms are related to the production of hormones whose concentration may not yet be high enough to be felt. 12 ] If you haven’t planned your pregnancy, it’s much more likely that you’re expecting your next period right now.

Your body during the 3rd week of pregnancy

L’Early Pregnancy Factor

One day after fertilization, the ovary produces an immunosuppressive protein called Early Pregnancy Factor (EPF) whose function is to ensure that the embryo is not “recognized” as a foreign element by your body.

Beta hcg 3 week

The production of hCG increases throughout the first weeks of pregnancy until it reaches a peak concentration towards the eighth / twelfth week, when it stabilizes or begins to decline.

hCG is produced to support the production of estrogen and progesterone by the corpus luteum.

The higher the hCG level, the more obvious the pregnancy symptoms will be.

Progesterone, estrogen and implant

About seven days after fertilization, the trophoblast attaches to the endometrium, the lining tissue of the uterus, and penetrates it. This process is called implantation (but also nidation or nesting).

Progesterone is a hormone whose main function is to prepare the lining of the uterus to favor implantation.

During pregnancy the level of progesterone increases following a curve and favoring the growth of the fetus.

Estrogens , also hormones, perform several essential tasks during pregnancy :

  • increase the rate of blood flow in the placenta to get the fetus all the nutrients it needs to grow,
  • they increase the adipose component in the breast and take care of forming the lactiferous ducts, the channels that carry milk to the nipple.

During pregnancy progesterone and estrogen are secreted by different organs:

  • from the corpus luteum, in the first weeks,
  • from the placenta and ovaries in the 2nd trimester of pregnancy,
  • only from the placenta in the third trimester.

Belly at 3 weeks pregnant

At this point in your pregnancy, you still don’t notice obvious changes in your body, such as the growth of your belly, therefore, you will easily wear the most comfortable clothes you have in your wardrobe, but soon you will have to resort to maternity trousers  , at the very least, resort to a widening band.

So let’s see what are the symptoms of implantation and, subsequently, what the embryo looks like in this stage of growth.

Pains and symptoms in the third week of pregnancy

During the 3rd week of pregnancy, the other symptoms may consist of:

  • an increase in basal body temperature;
  • crampetti uterini;
  • mood swings due to hormonal changes;
  • a decrease in the consistency of the cervical mucus, or in vaginal discharge linked to the implantation of the embryo (if these are accompanied by severe pain, it is advisable to consult a doctor, because there could be an ectopic pregnancy);
  • headache and tiredness, due to increased progesterone levels;
  • frequent urination (in fact, both the increase in hormones and the pressure of the uterine volume that “pushes” against the bladder could lead to an increase in the daily episodes of urine expulsion);
  • a large appetite; 
  • a strong sense of tension in the breast, can give you the feeling that you are expecting a baby. 

Other symptoms may also occur during this time, such as morning sickness, sore breasts, food cravings , fatigue, bloating, bloating, mood swings, lower back pain and – albeit infrequently – diarrhea.

For the reasons mentioned above, do not be alarmed if you think (or if you already know) that you are in the 3rd week and, despite this, you do not feel any of the symptoms described above: in about ten days or less, they will not fail to make themselves felt!

Now, the watchword is: «no scaremongering». He tries to distract you and relax you, perhaps by reading a good book.

In case of a twin pregnancy

According to some sources, the symptoms of a twin pregnancy would not be particularly different from those of a pregnancy with a single fetus, but could be felt earlier, and in a clearer and more intense way.

This is probably due to the higher production of  human chorionic gonadotropin that occurs in the case of a twin pregnancy. However, the rule always applies that each pregnancy is a case in itself, and therefore also its symptoms. 

The embryo in the third week of pregnancy

The embryo, or the fertilized egg that has undergone (at least) one cell division – at this time we are not yet talking about a fetus – develops as described below:

  1. descends along the fallopian tube;
  2. it is fertilized only by the single sperm that passes a selection with about 300 million other sperm (before being able to reach the ovum, pending fertilization, this “winning” sperm must rise in the uterus for about 15-20 centimeters. It takes about 20 minutes for it to penetrate the thick outer layer of the egg);
  3. over the next eleven hours, the nuclei of the sperm and egg fuse together, completing the fertilization process. The zygote, from the ancient Greek ζυγωτός (zygōtós) – which means united or yoked – is the cell that is obtained with fertilization. The egg and sperm contain 23 chromosomes each. These combine and then go on to form the zygote containing 46 chromosomes. Since the nuclei merge, the individual’s genetic heritage is defined, is fixed, and already holds all the hereditary characteristics including hair color, eye color and build.
  4. The newly formed zygote travels down the fallopian tube towards the uterus where it attaches to the uterine wall and then develops further. This process is called implantation. The implantation process is completed between six and twelve days (usually nine days) after ovulation and fertilization. Meanwhile, the zygote continues to divide forming a grouping (cluster) of about 100 cells which is called a blastocyst . In rare cases (about 2% of pregnancies), the blastocyst can attach itself somewhere in the fallopian tube, ovary, abdomen, or cervix, causing an ectopic pregnancy . At the end of this week, the embryo it measures about 0.1 mm, and is not detectable by scanning tests such as ultrasound .
Tests and examinations during the third week of pregnancy

A pregnancy is usually detected  by assessing hCG levels  in two different ways:

  • in the urine,
  • in the blood.

In the urine, a pregnancy test can show positive results only during the 3rd week of pregnancy, i.e. the IV-V week after the implant we have mentioned.

Blood tests, on the other hand, are able to show a positive result as early as 3-4 days after the implant, and are in any case the safest way to confirm pregnancy.

Unless you haven’t already, this period could be the right time to have a pre-conception visit.

3 weeks pregnant how many months is it?

If you are 3 weeks pregnant then you are in the first month of pregnancy. The birth is still about 8 months away.

Some useful tips for a peaceful expectation and for a healthy baby

We have already mentioned that during the 3rd week of pregnancy most women still do not know they are pregnant. Those who already know this have the opportunity to start making the right changes to their diet and lifestyle right now:

  • First, it is good to start taking note of the evolution of your weight to have a trace of how – over the next nine months – you are gaining weight. In case you don’t already have one, we recommend purchasing a digital bathroom scale.
  • It is advisable  to stop taking alcohol and tobacco  and to reduce  caffeine .
  • In recent decades, many studies have shown that there is an association between  maternal oral infections and poor pregnancy outcomes . In addition, it should be added that pregnancy represents a very stressful period for a woman’s teeth and gums. So start taking great care of your mouth even by buying a new toothbrush: maybe, if you don’t already have one, try an electric toothbrush and dental floss.
  • Starting this week, before undergoing  X-rays, even if only for dental treatment, do not forget to inform the health personnel in charge of your pregnancy. They will then decide if and how to proceed.
  • Avoid being around harmful substances, such as pesticides,  which substances could interfere with cell division.
  • It is useful to take prenatal vitamins containing folic acid, following the doctor’s instructions, which are useful for preventing most of those defects concerning the brain and spinal cord of the child, which could occur during the first weeks of birth .
  • And finally, it could be useful to be followed not only by a doctor, but also by a midwife (not to be confused with the professional figure of the gynecologist) who the Ministerial Decree of 14 September 1994, No. 740 qualifies as “the healthcare operator who , in possession of the qualifying university diploma and registration in the professional register, assists and advises the woman during the gestation period, during childbirth and in the puerperium , conducts and completes eutrophic deliveries with her own responsibility and provides assistance to the newborn “.

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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