In week 3 of pregnancy, a lot is happening in your body—often without you noticing. Fertilization now takes place, and the egg then embarks on its exciting journey. Once it has implanted in your uterus, you are “officially” pregnant! Here, you’ll find out exactly what is happening in your body this week and what matters most right now.

3rd Trimester: What's changing for you

You probably haven’t noticed much yet, but with week 3, your first “real” week of pregnancy begins. Once a sperm cell reaches the egg in the fallopian tube, breaks through its membrane, and they fuse, the egg is fertilized and is called a Zygote . It continues its journey through the fallopian tube to the uterus and begins to divide. In a very short time, numerous cells with different functions form—together, they will soon develop into a tiny human. This cell structure is called a Morula or Mulberry seed , because its appearance can be compared to that of a knobby mulberry. Around the fourth day after fertilization, the morula forms a fluid-filled cavity inside and develops into the so-called Blastocytes or Blasenkeim. It already consists of around 200 cells and is smaller than one millimeter. From the inner part of the blastocyst, the so-called Embryoblast , the embryo soon develops. From the other part, the Trophoplasten , the Placenta and umbilical cord develop, which will later nourish the embryo. Five to six days after fertilization, the blastocyst implants into the uterine lining and establishes a connection with your bloodstream. This way, your baby can be supplied with all the essential nutrients for rapid growth. Towards the end of the 3rd or the beginning of Week 4 of pregnancy , you are now officially pregnant after successful implantation.

Pregnancy signs

Most women don’t know they are pregnant in the 3rd week of pregnancy. It’s almost unbelievable that you usually don’t feel much of the new life forming inside you. Even on an ultrasound image in the 3rd week of pregnancy, there would be little to see besides a thick uterine lining. Pregnancy can usually be detected for the first time by ultrasound from the 5th week of pregnancy, once the gestational sac has formed.

Some women experience a slight pulling sensation in the abdomen during implantation, which occurs at the end of the 3rd or in the 4th week of pregnancy, similar to menstrual cramps. It’s also possible that you notice light, bright red bleeding at this time, known as implantation bleeding ( Nidationsblutung ). This can occur when small blood vessels are damaged during implantation into the uterine lining
. If you are hoping for a pregnancy or have a suspicion, the bleeding might scare you, but it is completely harmless. And even if you don’t notice any pregnancy symptoms at this early stage, that’s perfectly normal and no reason to worry.

3rd Trimester: Development of Your Baby

As soon as the sperm penetrates the egg, 23 chromosomes from you and 23 chromosomes from the biological father combine to form a unique set of 46 chromosomes and a total of 40,000 genes. The fertilized egg already contains all of your baby’s genetic information, such as hair color and sex. Which combination of genes will prevail—and whether your baby gets mom’s or dad’s nose—will only be decided later during the embryonic phase. In the 3rd week of pregnancy, all genes are still present in duplicate.

Good to know: When is a pregnancy test "reliable"?

A pregnancy test measures the level of the hormone hCG in the body, which rises sharply, especially in the first months of pregnancy. In the 3rd week of pregnancy, however, when the egg has not yet implanted or has only just implanted in your uterus, your body produces little or no hCG at all. The level is therefore still too low to be detected by a pregnancy test. Pregnancy can be reliably confirmed by a blood test from the 4th week or a urine test from the 5th week of pregnancy—so you’ll need to be a little patient.

This is now important

• The risk of miscarriage is particularly high in early pregnancy. More than half of fertilized eggs are lost before the 6th week of pregnancy, often before the pregnancy is even detected and frequently without being noticed. You can find more about the causes, signs, and treatment of pregnancy loss in the article “ Miscarriage “.

• As soon as you find out you’re pregnant, the rule is: alcohol and nicotine are off-limits, as these toxins can harm the embryo’s development.

• When it comes to your diet, it’s important to avoid certain things and focus on a healthy, balanced diet so your baby is supplied with all the necessary nutrients from the very beginning—nutrients it needs for healthy development.
  In the article “ Proper Nutrition During Pregnancy “ you will learn what you should pay attention to now.

• Most vitamins can be obtained in sufficient amounts through a balanced diet during pregnancy. However, the need for folic acid is especially high and cannot be covered solely through diet—therefore, it’s best to start taking folic acid when trying to conceive, or at the latest, at the start of pregnancy. You can learn more about the importance and correct dosage of the vitamin in the article “ ".

With our pregnancy calendar, we want to accompany you through this exciting time and provide you with relevant information, created in exchange with our
LILLYDOO experts. Nevertheless, the information listed here can
never replace personal consultation with your doctor or midwife. Always contact your healthcare professional with questions and for professional care.