Each Trimester

What are the Major Milestones During Each Trimester?

Pregnancy is one of the most precious things for any woman. Parenthood is filled with joy and cherishable moments. But the development of a single egg to baby causes excitement and increases your adrenaline also. There are various stages of baby development in pregnancy week by week. Pregnancy is divided into three phases called trimesters. In each trimester, your child meets the major milestones of life like heartbeat and long hair. Therefore, it is important to understand the phases of pregnancy in detail. The three phases of pregnancy are:

  • 1st Trimester: Week 1-12

  • 2nd Trimester: Week 12-24

  • 3rd Trimester: Week 24-40

Some doctors calculate the 42-week method:

  • 1st Trimester: Week 0-13

  • 2nd Trimester: Week 14-28

  • 3rd Trimester: Week 29-42

Here is a look at the various milestones achieved during each trimester:

1st Trimester:

Each Trimester

This is the first three months of pregnancy and the most crucial stage in pregnancy. In this phase, the organs of your little one are formed. Any deformity in the organ of the baby happens in this stage only. The major milestones of pregnancy week by week are as follows:

1)    4 weeks: At the end of 4 weeks, the ball of cells called blastocyst grows into the size of a poppy seed and officially becomes an embryo. After the embryo formation, the organs start developing until 6 weeks.

2)    5 weeks: During this time, the baby develops a heartbeat which beats twice the rate of an adult heart.

3)    6 weeks: At this time, facial features begin to form and the little buds for arms and legs are formed.

4)    8-9 weeks: Baby starts moving all the limbs, has earlobes and eyelids that are fused shut.

5)    10 weeks: Till this time, the embryo becomes the fetus. Various internal organs like kidneys, intestines, brain, and liver begin to function. Fingernails and toenails are also formed by this time. Bones harden and genitalia are formed externally.

6)    12 weeks: You may be able to hear the baby’s heartbeat at a prenatal checkup.

2nd Trimester: 


Milestones achieved during this period are:

1)    14 weeks: Baby’s kidneys start working properly. They produce urine which is released into the amniotic fluid. The baby can make facial expressions and may even suck his or her thumb.

2)    15- 16 weeks: You can see the baby’s gender in an ultrasound between 16-20 weeks. Baby can also see light from outside the womb and begins breathing amniotic fluid to develop his or her lungs.

3)    18 weeks: You can feel the baby’s movement inside your womb. Other people can also notice baby movements from outside your stomach.

4)    23 weeks: Baby movement further develops and hearing improves. He can feel you dancing or running.

5)    24 weeks: taste buds develop. Brain and hair grow quickly. Your baby is now a foot long and weighs over a pound.

6)    27 weeks: Your baby can suck thumb at this time. The lungs are developing at this stage. The baby will inhale and exhale amniotic fluid. Baby can now sleep and wake at regular intervals. He or she can now even open and close the eyes.

3rd Trimester:

1)    28-32 weeks: Your baby begins dreaming and has eyelashes for better eyesight. Weight increases up to 3 to 4 pounds and fingernails and toenails further grow.

2)    34 weeks: Lungs and central nervous system further develop and skin becomes soft and smooth.

3)    37 weeks: Your baby is now considered as an early term but ideally should not be born.

4)    39 weeks: Now the baby is fully termed and is ready for birth. The average weight of the baby is now 7.5 pounds and the length is about 20 inches.

5)    41 weeks: Now the baby is considered as late-term and anything post 42 week is post-term. Check with your doctor to discuss your pregnancy week by week.

Author – Vidya Kanekar

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