Pregnancy Week by Week

Pregnancy is counted as nine months, or 40 weeks, long. There is a slight anomaly here as an average baby generally spends about 38 weeks in the womb. This is because pregnancy is counted from the first day of the woman’s last period. Conception generally happens about two weeks after that. The 40 weeks of pregnancy are divided into three trimesters:

First Trimester: 1 to 12 weeks

Second Trimester: 13 to 28 weeks

Third Trimester: 29 to 40 weeks

During the course of these 40 weeks, the baby transforms from a fertilised egg to a fully grown human. The woman also experiences major changes in her body. If you are too wondering about what happens to the baby and the mother throughout her pregnancy, here is the week-wise changes that happen:

First Trimester

As you already know that the first trimester lasts from week 1 to 12. Here are the changes that happen during this period:

Week 1

As you already know that the pregnancy is calculated from the first date of your last period, hence this week comprises of that. Do note that you haven’t conceived as yet.

Week 2

At the end of this week, the fertilisation of the egg takes place.

Week 3

In this week, the fertilised egg slowly moves down the fallopian tube towards the uterus, where it gets implanted for the remainder of the pregnancy.

Week 4

At this stage, the baby is smaller than a grain of rice. However, the rapidly dividing cells are working to develop major body systems, such as the digestive system.

What Happens To You: The woman generally experiences no symptoms for the first four weeks.

 Week 5

The central nervous system, which comprises the brain and spinal cord, starts to develop.

What Happens To You: This is generally the time when you might miss your first period.

 Week 6

The baby is developed enough to be called an embryo. It grows 3mm long by week 6.

What Happens To You: As your hormones change, you will experience other pregnancy-related symptoms.

Week 7

By week 7, the placenta, an organ responsible for transporting oxygen and nutrients to the baby, gets developed. It also gets burrowed into the wall of the uterus to get the baby oxygen and nutrients from the mother’s bloodstream. The amniotic sac, which is a fluid-filled bag-like structure, also develops. It houses the baby inside the mother’s womb throughout the pregnancy. The baby’s heart also starts beating

What Happens To You: This is the time when you might start experiencing a range of symptoms. You might feel more tired, your breasts will get tender and sore, you will experience nausea and vomiting, which comprises the ‘morning sickness’, and you will have the urge to pee often. 

Week 8

The baby continues to grow and by the eighth week, it grows about 1.3 cm in length. The spinal cord develops and looks like a tail. The baby’s developing head gets disproportionately larger than the rest of the body. 

What Happens To You: You might experience symptoms similar to those in week 7.

Week 9

Some of the baby’s vital body parts, such as the eyes, mouth, and tongue, start to form. The developing muscles allow the fetus to move around. Also, the red blood cells start to form.

What Happens To You: As you know that the breasts start growing during pregnancy. By week 9, they grow big enough that you might need a supportive bra. You might also have mood swings, which means you might have episodes of elation and gloom. Do not worry, as these are normal and generally go away by the second trimester. Another symptom you might experience by this stage is an increase in vaginal discharge. However, if the discharge looks strange and smells really bad, you must tell your doctor, as it might be because of an infection.

Week 10

By this time, the baby grows about 2.5 cm long and transforms from an embryo to a fetus. The body parts continue to form, the fingers and toes start to develop. By week 10, the baby’s brain gets active.

Week 11

The baby’s teeth start forming and the heart continues to develop.

What Happens To You: You might get headaches. These are largely due to the major body changes that occur during the initial pregnancy. You can contact your doctor to know how to deal with headaches.

Week 12

The last week of the first trimester, the baby’s fingers and toes start to look distinct by week 12.

What Happens To You: As you know that pregnancy symptoms differ from woman to woman. Some women experience constipation. Some also get stomach or abdominal cramps from time to time. This is nothing to worry about and might be a result of constipation, or gas, or loosening ligaments to support the growing uterus.

This trimester lasts from week 13 till 28. Here are the changes you and your baby will experience:

Week 13

The fetus grows about 7cm long by the start of the second trimester. The baby can also swim well in the amniotic fluid.

What Happens To You: In most women, morning sickness starts fading by the 13th or 14th week. After the tiring first trimester, they also get their energy back by this stage. Many women also experience a rise in their sex drive. This might be due to the pregnancy hormone or the rise in blood flow in their pelvis area. The baby bump also starts showing by this week.

Week 14

By week 14, the baby’s eyelids develop and he/she can even cry, however, mutely. The baby can suck his/her thumb and the nails on the toes and fingers start to develop.

What Happens To You: You experience symptoms similar to that in week 14.

Week 15

By this stage, the baby starts to hear. He/she can hear some faint noises from the outside world, sounds from your digestive system or that of your heart beating. Although the fetus’ eyes are closed, the baby’s eyes get sensitive to light outside.

What Happens To You: As your womb gets heavier, it puts pressure on the lower back. So, you might experience some aches and pains in the lower back. 

Week 16

The baby grows 14 cm long. His/her eyelashes and eyebrows develop. The tastebud on the tongue also forms.

Week 17

By this time, the baby grows enough to weigh about 150 grams. Although the eyelids are shut, the baby can move the eyes. He/she can also open and close the mouth. The fingerprints develop and the baby’s hands now develop a firm grip.

Week 18

The baby can move around. However, you might not be able to feel it, especially if it is your first pregnancy.

Week 19

The baby continues to develop and keeps putting on weight.

What Happens To You: Most moms feel their baby’s first movement around 17 to 18 weeks of pregnancy. However, first-time moms generally experience that somewhere between the weeks 18 to 20. You might also experience pain in your pelvis and/or hips. This might be due to the hormonal changes or your growing baby bump.

Week 20

By week 20, the baby grows 21 cm long. The baby’s genitals can be distinguished now. 

Week 21

By week 21, the baby grows enough to weigh 350 grams. This is also the time when the baby starts weighing more than the placenta. Although the placenta grows throughout pregnancy, but by week 21, it doesn’t grow as rapidly as the baby itself. Also, the baby gets covered with a thin, soft covering of hair, called lanugo. Its purpose isn’t fully understood yet, however, it is believed to keep the baby at a fine temperature.

What Happens To You: You start being hungrier by this time. However, you must continue to have a balanced diet for the sake of your health and that of the baby.

Week 22

This is the time when your baby starts following a pattern for sleeping and waking up. However, this might not be similar to the normal sleep pattern. This means that when you are deep asleep at night, your baby might be wide awake.

What Happens To You: Many women get stretch marks on their belly, breasts, and thighs around this time.

Week 23

The lungs continue to develop and start practicing breathing for once the baby is born. However, till that time, all of the baby’s oxygen demands are met by the placenta.

What Happens To You: Many women suffer from piles, or hemorrhoids, during this stage.

Week 24

The baby grows 33 cm long. The eyelids were fused up until this time. By week 24, the upper and lower eyelids separate, allowing the baby to open and close eyes.

Week 25

Your baby can now respond to touch and sound. In fact, he/she may jerk or kick to loud noise. The baby also gets hiccups, which you can also feel. The baby also urinates in the amniotic fluid.

What Happens To You: Swelling in the face, hands, and feet is quite common, and is generally caused by water retention. However, if you have it, you must inform your doctor to rule out any complications. The growing baby bump might also make your back hurt more.

Week 26

This is the time when your baby’s eyelids open for the first time and it is about time that he/she is able to start blinking.

What Happens To You: By this time, you might notice that you leak pee whenever you cough, sneeze or put pressure on your stomach. This is because pregnancy and childbirth make the pelvis muscles weak.

Week 27

The baby’s body parts continue developing, such as the heart, brain and the digestive system.

What Happens To You: Having nosebleeds are common during pregnancy. It is largely caused by hormonal changes.

Week 28

By week 28, the baby grows 37 cm long and weighs about 1 kilogram. Until now the baby’s head was disproportionately larger than the rest of the body. But by week 28, the body develops enough to catch up with the head. This means that the baby looks in better proportion.

What Happens To You: Many women suffer from heartburn and indigestion. Although not harmful, these can make you uncomfortable. However, you are advised against taking any over-the-counter medication. If you are too uncomfortable, consult your doctor, who might prescribe you a safe drug.

The final leg of your pregnancy, the third trimester stretches from week 29 till 40.

Week 29

By week 29, your baby starts moving a lot and you can feel the movement very well.

What Happens To You: From the third trimester onwards, many women start experiencing breathlessness. Swollen ankles are also common in pregnancy.

Week 30

The baby starts gaining muss, as a result, starts appearing less wrinkled. Lanugo, the thin, soft hair that had covered the baby till now, begins disappearing.

What Happens To You: From week 29 till 32, having leg cramps at night is quite common. As it can make it uncomfortable for you to sleep, try putting a pillow in between your legs. You might also have the urge to urinate often.

Week 31

The baby’s eyes get developed enough to focus. The lungs continue to develop.

Week 32

As you know that the baby moves around a lot. By week 32, the movement gets strong and better coordinated. However, the baby spends most of the time sleeping. The baby starts moving into the head’s down position, required during birth. 

Week 33

By this time, your baby’s brain and central nervous system get fully developed.

What Happens To You: Owing to the hormonal changes and the uterus pressing against the stomach, you might continue to have heartburn and indigestion. 

Week 34

The baby’s bones start hardening. This applies to every bone, except skull bones, which continue to be soft until delivery to make the baby’s passage through the birth canal easier. 

Week 35

The baby gets into the curled-up position with the legs across the chest. There will be little room in the uterus to move around, but your baby still will. In case you are having a baby boy, his testicles will descend from the abdomen into the scrotum.

What Happens To You: Some women get into labour before 37 weeks. This is known as premature birth. If this is the case with you, your baby will be kept in special care for some time.

Week 36

By this time, the baby’s length is about 46 cm. The baby also starts moving into your pelvis area to be born.

What Happens To You: You might start having contractions, which are dull and irregular. These are common and are known as Braxton Hicks contractions or false labour. You can understand these as your uterus’ preparation for contraction during birth. However, if they get strong and irregular, then it can be a sign of the start of labour.

Week 37

At week 37, the pregnancy is considered full-term. This is the time when your baby is ready to be born.

Week 38

Your baby might poo in the amniotic fluid. This is generally closely monitored by the doctor as it can be a sign that your baby is stressed out.

Week 39

Most women go into labour around this time.

Week 40

The pregnancy is generally 40 weeks long and your baby might be ready or is born by this time. However, if this doesn’t happen, the doctor might wait for a week or two more, and then will induce labour for the child to be born.