Pregnancy Stages: Week by Week Fetal Development

Pregnancy creates havoc of hormones in the body which usually settle down after delivering the child. Women are often used to such hormones changes as they experience them throughout their menstrual phase. However, some women are prone to more hormone fluctuations and symptoms related to it.

The body reacts to various hormones and shows various symptoms to let know what exactly is going on in the body. Although the symptoms most often follow similar patterns in every cycle, sometimes they may go different and unusual.

Pregnancy is a similar process for every woman experiencing almost the same symptoms, however, only a few women will have complexities during that phase which should then be monitored well.

How To Monitor Progress During Pregnancy?

The following week by week progress of the baby’s development in the pregnancy period is a charm for a first time, mom, as she gets to know what is going on within her.

Technology has even introduced 3D ultrasounds to have a clearer look of the baby before it comes to the world. It is often recommended to have at least 1 2D ultrasound to known of everything is going well.

A detailed ultrasound will usually take place at weeks 20 of the pregnancy which shows every possible detail of the growing baby and rules out any risk factors.

It is important to know about the different phases of pregnancy so as to have an idea about what to expect when. Here are the three trimesters mentioned with the details of the week by week progress to know how the pregnancy progresses.

pregnancy stages week by week
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First Trimester of Pregnancy

The first trimester is usually the most critical for a pregnancy to get stable as most of the organs form during this period. This period comprises of the first 12-13 weeks after which there are only very few chances of miscarriage. Since everything is under control after crossing the first trimester, people usually now find it safe to disclose the news to others.

After a good 12 weeks, women usually get to hear the heartbeat at the doctor’s appointment through a device. This will be done every month to ensure the little one is safe and sound inside.


  • Bloating
  • Mild cramping
  • Mood swings
  • Morning sickness
  • Fatigue
  • Sore breasts
  • Heartburn
  • Frequent urination

Weeks 1-4: Pregnancy is achieved during the mid-cycle when ovulation occurs and therefore the first two weeks of the cycle are usually only added to date the pregnancy as the body just prepares itself for the egg release during that period.

Week 3 is when the egg implants in the uterus but you may not feel it now as it gets to the size of a poppy seed in week 4. Most women are unaware of their pregnancy until 5 or 6 weeks as the symptoms then start to show up.

Weeks 5-8: Women get to know about their pregnancy as soon as they miss their period which is usually the first sign. Although it may take another good 7-10 days for the hCG hormone to be detected in the urine test, this will only build up excitement to know the answer. By week 6 or 7, most women have an answer and start their emotional ride of pregnancy.

The embryo is the size of an orange seed at week 5, size of a blueberry at week 7, and that of raspberry at week 8. At week 6, the baby’s heartbeat is detected by the ultrasound on the screen which is the first thing to assure the little one has a life.

Weeks 9-12: Entering the third month of pregnancy, women may still have symptoms of morning sickness as the body is producing extra hormones to adjust the new little one inside. These hormones will settle down as soon as you enter your second trimester.

Most of the baby’s development takes place during the first three months after which the baby’s other features are formed. During these weeks, the baby is busy building muscles, bones, and cartilage. The baby will begin to look more like a human now by week 11 and will become the size of a plum at week 12.

Second Trimester of Pregnancy

The second trimester of pregnancy is the most favorable period for a woman as the hormones get settled and women start feeling more energetic and calm. This is a period to rejoice your pregnancy period as the growing belly will only start coming in the way from the third trimester. This is the ideal time to have some sexy time with your partner as you get in the mood.


  • Constipation
  • Decreased fatigue
  • Visible veins
  • Food cravings
  • Increased appetite
  • Stuffy nose
  • Increased Vaginal discharge
  • Bleeding gums
  • Backaches
  • Stretch Marks
  • Fetal Movement

Weeks 13-16: As you get along with pregnancy in the second trimester, you feel more relaxed as you have passed the most critical time. You may now expect nausea to go away and your mood will be elevated. As your baby grows, it starts kicking its legs and flexes its elbows although its too soon to feel them.

The baby has become the size of your fist by week 14, a navel orange by week 15, and that of an avocado by week 16. Your baby’s eyesight and eyelashes are built rapidly during this period.

Weeks 17-20: This is the time when the baby is still developing its features and starting to respond to the mother’s touch although it may not be felt until 20 weeks. The baby has now started practicing sucking and swallowing.

By week 18, your baby has reached the size of a sweet potato and you may start feeling the movements anytime from now. 20 weeks is known as the mid-phase of pregnancy when you are halfway through.

You will be advised to have a detailed anatomy scan to have a view of your growing baby. This is may take some time as many features are looked upon in this ultrasound including the gender!

21-24: The baby starts giving response and movements can be felt from this period. This is the time to feel your baby moving for the first time inside your body. The linea nigra is visible on your growing tummy by this period while the belly button may be popping out.

Third Trimester of Pregnancy

The third trimester brings you closer to delivery time which can be fearful for some women. You may start hearing other women’s experiences but it is important to keep yourself calm. Every woman is different and will have different experiences


  • Swollen feet
  • Need for more sleep
  • Blurred vision
  • Snoring
  • Leg aches
  • Tingling hands
  • Itchy belly
  • Dizziness
  • Migraines
  • Fetal movement

Weeks 25-28: Your baby is now the size of cauliflower and is preparing itself for the first breath. The baby will open his eyes and reaches the size of eggplant by week 27. The baby starts coughing, hiccupping, and blinking during this period.

Weeks 29-32: Your baby now reaches the size of cabbage and its senses start to increase. The baby’s brain gets smarter as it gets ready to enter this world. The baby now gets a boost for the immune system.

Weeks 33-37: The baby now gets as big as the head of lettuce. A baby is growing rapidly and the baby’s head now weighs more to exert pressure on the bladder. On reaching week 36, the baby’s bones get ready to rock and roll.

Weeks 38-40: The doctor may now check for labor signs as you reach the end of pregnancy period. Your baby is now producing surfactant which will help him breathe.

Also, colostrums is produced by the mother as a precursor to breast milk. At 38 weeks pregnant sharp pain in left side can be experienced as the baby is turning and breathing continuously.

Weeks 41-42: You may now start feeling the signs of labor while the baby’s brain development is in high gear. Week 40 is known officially as the end of pregnancy.

However, babies are commonly overdue the date and there is nothing to worry about if this happens. Just hang in there and wait for the right time. You may reach 42 weeks for the actual delivery to take place.

Khadija Ahmad

An author at Ask Health News, Khadija has good experience in Health And Physical Education and delivers her research work to entertain readers. Her words reflect creativity and intellect as she succeeds in shaping them into interesting articles for readers. Email: khadija@askhealthnews.com

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