1st Trimester

Fetal Development

First Trimester (First Three Months)

First of all, congratulations. You are pregnant and expecting a baby. You are probably wondering how your baby is growing and developing. Here we will tell you how your baby develops week by week in the womb during the first trimester. Here you will find answers to all your questions: “What does your baby look like, how big is it, when will the heartbeat start?” and so on.

Week 1 (Preparation Period)

It may sound strange, but in the first two weeks of pregnancy you are not really pregnant. Yes, you read that right. Pregnancy can only start two weeks after your last menstrual period. When calculating your due date, your doctor counts 40 weeks from your last menstrual period. This period also includes the period when you are not pregnant.

Week 2 (Fertilization = fertilization)

In the oviduct, the sperm and egg cell form a single cell called a zygote. If more than one egg cell is released and fertilization takes place, more than one zygote can develop. The zygote has 46 chromosomes, 23 from the mother and 23 from the father. These chromosomes contain the genetic structure that will determine your baby’s gender, eye and hair color, height, weight and face shape. They also contain the genetic structure that determines intelligence and personality traits. After fertilization, the zygote travels down the oviduct into your uterus. During this journey, the cells continue to divide rapidly and become a cluster of cells resembling a small raspberry. The inner cells will form the embryo and the outer cells will form the membranes that will nourish and protect it.

Week 3 (Implantation=Implantation)

When the zygote has about 500 cells, we call it a blastocyst. Once in the uterus, the blastocyst attaches to the uterine wall to feed. Thus, the placenta (the partner) begins to form, which will provide nourishment for your baby throughout your pregnancy. By the end of this week, the pregnancy test will be positive.

Week 4 (Embryo period)

The embryo stage begins in the fourth week. Your baby’s brain, spinal cord, heart and other organs are already forming and are about one millimeter in size. The embryo is made up of three layers. The outermost ectoderm layer forms the neural tube, the part that will develop your baby’s brain, spinal cord, nerves and spine. The middle layer, called the mesoderm, forms your baby’s heart and the vessels that will circulate blood. This is also where muscles, bones, kidneys and reproductive organs are formed. The innermost layer, called the endoderm, forms the lung, intestine and bladder.

Week 5

Your baby is a few millimeters long, about the size of the tip of a ballpoint pen. In this week, your baby’s heart and circulatory system is forming and its heart is beating. Even if you cannot hear it yet, the heartbeat can be detected during an ultrasound examination. Thus, your baby’s circulatory system is the first system to start working.

Week 6

Growth is accelerating this week. The neural tube along your baby’s back is closing and the heart is beating in a regular rhythm. The shape of your baby’s face is beginning to emerge and the mouth and inner ear are forming. The respiratory and digestive systems begin to develop. Connective tissue, ribs and muscles will form from the tissues in the center of your baby. Arms and legs will develop from the small ridges on the sides.

Week 7

Your baby has reached 8 millimeters in length. That means it is slightly bigger than a pencil eraser and weighs less than an aspirin. The umbilical cord between the placenta and your baby can now be seen more clearly. The brain is beginning to form and the skull is still transparent. The arm is getting a little bigger. Your baby’s face becomes a little more distinct. Mouth, ears and nostrils become visible.

Week 8

Your baby’s fingers and toes are starting to form. Elbows and wrists become visible. Eyelids start to form. The ears, upper lip and nose are more prominent and the baby’s height reaches 1-1.5 cm. Your baby’s heart is now highly developed and beats 150 times a minute, twice as fast as a normal adult.

Week 9

Your baby is 2.5 cm long and weighs 3.5 grams. The appendage on the coccyx is gradually diminishing and it is beginning to resemble a human being. Its head, which makes up half of its entire body, is tilted towards its chest. Nipples and hair follicles begin to form. The pancreas and gall bladder take their place. The testicles or ovaries begin to develop. From this week onwards, your baby may start to move, but you won’t be able to feel it.

Week 10

From this week onwards, your baby’s organs are becoming well defined. The embryonic tail disappears completely. The fingers and toes are completely separated. The bones of the skeleton are also beginning to form. Also from this week, your baby’s brain starts to produce 250,000 new nerve cells every minute. The eyelids are no longer transparent and the ears are starting to take their final shape. The roots of the teeth are also beginning to form. If your baby is a boy, his testicles will start producing the male hormone testosterone.

Week 11

By the end of this week, your baby’s external genitalia will be visible. The sex of your baby is now visible. From this week until week 20, your baby’s weight will increase 30 times and its length will increase 3 times. This will happen when the blood vessels in the placenta grow and increase in number, so that it receives enough nutrients.

Week 12

Your baby is now called a fetus. It is about 7-8 cm long and weighs about 20-25 g. The fingernails and toenails are forming. The jaw and ear are taking their final shape. If you first choose a healthy lifestyle for yourself, this will have a positive effect on the development of your baby. It is even better if you start before conception.

Please note the list of do’s and don’ts listed below;

What to do:

Take vitamin and folic acid supplements prescribed by your doctor.

Watch your weight. Do the exercises recommended by your doctor regularly.

Eat a healthy diet. Watch out for stress and other health problems.

Have regular check-ups. Be sure to tell your doctor about all the medicines you are taking.

They will not be made:

Avoid smoking and alcohol. Do not use drugs.

Popular Topics

1st Trimester

2nd Trimester

3rd Trimester

Air Travel during Pregnancy

Amniocentesis

Antidepressant Medication Use in Pregnancy

Bed rest during pregnancy

Birth Control Methods

Changes that occur during pregnancy

Depression in Pregnancy

Development of the Mother’s Body According to the Months of Pregnancy

Diabetes in Pregnancy

Diabetes in Pregnancy (Gestational Diabetes)

Ectopic pregnancy

Exercise in Pregnancy

Femilift

Foot swelling during pregnancy

Genetic Diseases

High Blood Pressure in Pregnancy and Preeclampsia

How Does Pregnancy Start?

How Should Weight Gain Be During Pregnancy?

How to know when labor has begun

Hygiene during Pregnancy

Identification of Genetic Diseases in Pregnancy

If you no longer want children

Infectious Diseases in Pregnancy

Maternal Psychology During Pregnancy and Puerperium

Medicines in Pregnancy

Miscarriage During Pregnancy

Mole Pregnancy

Multiple pregnancy follow-up, delivery and postpartum

Nausea – Vomiting in Pregnancy

Normal Birth, Cesarean Birth, Water Birth, Hynobirthing

Nutrition Guide during Pregnancy

Placement of the Placenta Down (Plazenta Previa)

Placenta Previa

Postnatal care

Postoperative patient information

Postpartum Depression

Postpartum Exercise