Sunday , 20 October 2019
Breaking News
Home / Prenatal Care / Pregnancy Trimesters | Stages of Pregnancy week by week

Pregnancy Trimesters | Stages of Pregnancy week by week

The normal pregnancy period ranges between 40 and 42 weeks, Usually, Pregnant women must reach at least the 37th week of pregnancy to give birth to a fully-developed baby which is free from any congenital abnormalities that be with incomplete pregnancies which in the labor is usually done before the 37th week.

The normal period of pregnancy that is required for the pregnant woman to give birth to a fully-developed fetus is called “Term of pregnancy” normally as mentioned before it is 37 weeks, If she gave birth to her child before that time, birth would be called “Preterm labor”.

These 42 weeks are divided into three parts called pregnancy trimesters, each trimester includes three months or 12-14 weeks (fig. 1), Read on to know more in detail about stages of pregnancy week by week.

The first trimester of pregnancy

The first trimester of pregnancy starts from the first week of pregnancy until the 12th week.

This trimester is the most critical for the development of the baby, And, most fetal abnormalities are common in the first trimester.

Symptoms of pregnancy during the first trimester

  • Repeated Nausea and Vomiting, especially in the morning.
  • Craving and Aversions, e.g: increased appetite to chocolate while decreased to meat.
  • Raised smell sensation.
  • Psychic disturbances and mood swings.
  • Fatigue and easily tiredness.
  • Increased emotional feelings due to the hormonal changes.
  • No breast changes except, just mild tenderness especially in the first pregnancy due to the opening of milk ducts.

Fetal developmental milestones in first trimester

  • Firstly, the sperm from the man meets the egg from the woman at the outer part of the fallopian tube in the uterus to form the zygote.
  • Then, the zygote will divide repeatedly to form the primitive human baby which acquires the initial shape of the human body by the end of this trimester.
  • The eyelids appear but it still closed as a protection of the eye.
  • During the first 5 weeks of pregnancy, the baby height is around 0.5 inches, and it becomes approximately 3 inches by the end of the first trimester.
  • The baby weight is around 3 ounces during the first trimester.
  • In the eighth week, you can hear The baby heartbeats on the ultrasound doppler in the Obst. clinic.
  • Also, during this week, baby can flex his fingers to make a fist.
  • At the end of the first trimester, the doctor can tell the parents the gender of the fetus whether the baby is male or female Because he can see the external genitalia clearly in the ultrasound device during this stage.

The second trimester of pregnancy

The second trimester starts from the beginning of the 13th week and lasts for 14 weeks i.e. until the end of the 26th week of pregnancy.

Symptoms of pregnancy during the second trimester

  • At the beginning of the second trimester, the pregnant woman feels Pain in the lower part of the belly, due to the stretching of the round ligament of the uterus which supports the uterus and keeps it in place (fig. 2).
    • This pain of the round ligament is dull aching, sharp, or stabbing pain, and the pregnant woman may feel it in one or both sides of the lower abdomen, also she may feel it at the groin.
    • The pregnant woman can feel this pain when she gets up from the bed or chair, or while sneezing, laughing, and coughing.
  • Nipple changes, it starts to be darker and turns from a pink color to be dark brown.
  • Stretch marks start to appear on the abdomen and the lower back.
  • Quickening (i.e. The feeling of the baby movements or kicks in the lower part of the abdomen) starts at the end of the second trimester, but it still weak.
  • Fatigue, Nausea, and Vomiting decrease, Although, craving and aversions may continue.
  • The abdominal belly starts to enlarge markedly.
  • At the end of the second trimester of pregnancy, the pregnant woman can feel mild contractions in the uterus which are normal and called “Braxton–Hicks contractions”.
Round ligament of the uterus
(Fig. 2) : Round ligament of the uterus

Fetal developmental milestones in second trimester

  • The baby height increases to be 12 inches.
  • Also, the weight of the baby raised to be more than one pound.
  • And, the major internal organs are formed during this trimester, such as:
    • The musculoskeletal system includes (bone, muscles, and joints).
    • Skin, Nails, and hair.
    • Eyebrows and Eyelashes.
    • Taste buds.
    • Footprints and fingerprints are also formed during this trimesters.
    • Red and white blood cells start to form.
  • Internal genitalia starts to develop in this stage, as the testis comes out the body to drop in the scrotum in the male baby, Also, the ovaries start producing eggs in the female baby.
  • At the second trimester, baby can hear the sounds from outside.
  • And, the baby starts to swallow the amniotic fluid to practice swallowing to can do suckling after birth.
  • Also, the baby acquires his regular pattern of sleeping and waking.

The third trimester of pregnancy

The third trimester of pregnancy starting from the beginning of the 27th week and lasts until the end of the pregnancy which normally is after the end of the 37th week of pregnancy.

Symptoms of pregnancy during the third trimester

During this trimester the pregnant woman starts to feel that she is not comforted because all symptoms markedly increase.

  • Baby movements and kicks become stronger.
  • The lower part of the leg and the feet swollen.
  • The breasts start to leak the milk.
  • Abdomen become more enlarged and intra-abdominal pressure increases which lead to:
    • Frequency of going the bathroom to urinate.
    • Reflux of stomach content.
    • Shortening of breathing.
    • Lower back pain due to the stretch of the ligament behind the uterus.
  • Braxton–Hicks contractions become marked and severe, also it increases gradually during the period of this trimester.
  • The pregnant woman may develop psychic disturbances at the end of pregnancy such as the anxiety of labor.
  • Also, Insomnia and mood swings may start at the end of pregnancy.

Fetal developmental milestones in the third trimester

  • The baby height increases to be 20 inches.
  • Also, the weight of the baby raised to be more than 7 pounds.
  • At the beginning of the third trimester, most internal organs are fully mature.
  • Although, there are some organs which are partially developed and become fully matured at the end of pregnancy and before delivery, such as the lung.
  • The baby will start practicing breathing movements as a preparation for it after birth.
  • The number, regularity, and the strength of the Baby movements increase and become more than 10 kicks per day.


There are three stages of pregnancy woman pass through, each one has different symptoms, signs, and characters of the growing baby.

The pregnant woman should follow up on her pregnancy with her doctor routinely to ensure that stages are passing normally.

The first trimester of pregnancy is the most critical one and the commonest in which fetal defects occur.

Don’t forget to tell us in comments below that you are passing which one of these stages of pregnancy.


About Diaa Asaad

Leave a Reply

Your email address will not be published. Required fields are marked *