Pregnancy: how your baby grows and your body changes

Pregnancy is a time of wonder and awe, when you are host to one of nature’s most prized phenomenons. If you are expecting, it is natural that you would want to know about whats going to happen to your body and how the baby will grow inside you. Therefore, a lot of information is available on the internet with week-to-week guides and ‘what-to-expect’ articles. However we present here a summary, or an overarching view of what happens during the three trimesters of pregnancy.

The three trimesters and the 40 weeks of pregnancy

Pregnancy begins with fertilization of mother’s ovum with father’s sperm in mothers tubes (fallopian tubes). This can happen only in the post ovulation part of your menstrual period, usually at least 14 days after the first day of your LMP (Last Menstrual Period). But, it is not possible to mark the exact date of fertilization. Therefore, doctors use the LMP to calculate how far along you are accurately.

Thus, the counting of weeks of pregnancy begins from nearly two weeks before the actual pregnancy happens.

The earliest that you can find out that you are pregnant, is on the expected day of your period, when you have a missed period.

So how do weeks correspond to trimesters of pregnancy?

Till 12 completed weeks from LMP is first trimester. From 13th week till 27 completed weeks is second trimester and from 28th week till the birth of the baby is the third trimester. So they are not exactly equal in timelength, as you can see.

Also, the trimesters are not set in stone. Some consider up til 14th week in first trimester and some count only uptil 24th completed weeks in second trimester. But, it does not matter so much, since the trimesters are just a way of dividing a continuous process of pregnancy for better understanding

How does the baby’s growth correspond to the three trimesters?

The product of fertilization, your future baby is called embryo for the first eight weeks of pregnancy and foetus thereafter, until it is born and called a neonate or newborn

First trimester- the baby gets its body structure and organs

Most pregnancies  happen in fallopian tube, where the fertilized embryo stays mostly for the next three days. Then it travels down to the uterus, where it gets latched on to the uterus wall and a placenta develops to transfer blood and nutrients from mother to the embryo. This process of latching on is called implantation and some women experience spotting and pain in abdomen at this time.

The embryo also develops a protective fluid filled bag around itself, which is called the amniotic sac. Inside the amniotic sac the embryo then undergoes rapid cell division, before it starts to form body structures. At first it looks like a bunch of grapes, then a tadpole and then the face starts to develop. Among vital organs heart begins to develop first. Then neural system and limbs start to develop, followed by other systems. This process is called organogenesis and it happens in first trimester.By the end of the third month, the baby is fully formed. All the organs and body parts are present and now have to mature.  Between days 17 and 56 is a vulnerable time, because that’s when the baby is most susceptible to anything that can affect normal growth.

By the end of the first month, the embryo is about 1/4 inch long only, by the end of the second month, it is about 1 inch long and weighs about 1/30 of an ounce. At the end of the third month, the baby is about 4 inches long and weighs about 1 ounce.

Second trimester: the organ grow and mature so that they can function properly

By the end of the fourth and fifth month, your baby is about 6 and 10 inches long and weighs about 4 ounces to 250-450 grams nearly. He/she will grow in weight to one to one and half kilogram by the end of second trimester

The heart, nervous system , faculty of hearing all start maturing. Baby can yawn or suck its thumb and also hear voices by 23rd week. Hair begins to grow in fifth month and eye open in the sixth month

Third trimester: baby grows in weight and important organs such as lungs mature

In this trimester, fat starts to get deposited below the skin, so the baby gais weight rapidly. Also, her reflexes develop so that she can do purposeful movements such as turing her head etc. The last organs to attain maturity are the lungs which are fully mature only at the end of 37-38 weeks

After this, both mother and child are just eagerly waiting to meet each other!

When and how can you feel the baby growing inside you?

Different expectant mothers respond differently to tests or signs of a baby growing inside them. So for some a positive UPT (Urine Pregnancy Test) itself may be enough to feel like a mom and bond with the unborn! But others may need something more tangible

The second instance when you can see or hear your baby’s heart is the ultrasound. Your doctor can show you the baby’s heart beating usually by end of 6th or 7th week of pregnancy on TVS (Trans Vaginal Sonography). You can hear the heartbeat on doppler ultrasound only by 11 weeks. By 14 to 16 weeks, your doctor can help you hear your baby’s heart beating by a handheld doppler in her clinic

Also around 20 weeks, your doctor may do a 3D ultrasound and show you your baby’s face and limbs. Sometimes you could see the baby yawn or flex her limbs etc.

But the most direct and overwhelming feeling for most women is when they feel the baby’s movements inside their tummy! Most women are able to feel these for the first time after 18-20 weeks in their first pregnancy. At first, it is a funny feeling or a flutter in the tummy but as the baby grows the kicks become more powerful. In the third trimester the baby moves as many as 30 times in an hour during some hours of the day

Baby’s response to your talking or music is the next big step! As early as week 18-19, some babies will respond if pushed. She recognizes soothing sounds by week 21-22 and by week 26 she can move to the rhythm of music!

What changes can you expect in your body in the three trimesters of pregnancy?

First trimester changes in expecting mother

Morning sickness, feeling of tiredness, tenderness of breasts and feeling of frequent urination are some of the first symptoms of pregnancy. The hormonal changes happening in the body lead to many different symptoms in the expecting mother. These include mood swings, food aversions, increased vaginal discharge and heart burn.

In the first trimester weight gain may or may not be there and the baby bump is rarely visible

Second trimester changes in pregnancy

The tiredness and morning sickness begin to settle. This is the most hassle free trimester of pregnancy. However mood swings may persist.

The hormonal changes lead to relaxation of blood vessels which can give you a pregnancy glow, but also can lead to bleeding gums, nose bleeds, headache etc.

The baby bump becomes visible by 13-14 weeks in most women and by 18-20 weeks it reaches just below the navel. By the end of second trimester it is above the navel.

In this trimester the body weight should grow by 300-400 grams/week

Also some hair growth and pigmentation can develop including a black line in the middle of abdomen below umbilicus or a brownish pregnancy mask

Third trimester changes in expecting mother’s body

In this trimester the increasing size and weight of the uterus carrying the baby can have pressure changes. These include constipation, which can lead to haemarrhoids and bleeding during defecation. It can also cause back ache and swelling of feet. The heart burn may worsen. Also, you could get stretch marks on the abdomen and on breasts due to their stretching during rapid growth

The body weight of the mother increases usually by 500-700 grams/week or more

The baby bump gradually reaches up to the margins of the rib cage and comes down a little in late third trimester when the baby’s head gets fixed in the mothers pelvis

When will the baby birth happen and what can you expect around that time

Most pregnancies which are planned to be normal vaginal deliveries end in child birth in the following manner. The expected date of delivery is calculated at 40 completed weeks from your LMP.  At the end of 38 weeks, the pregnancy would be a term pregnancy. Mostly between 38-41 weeks, women either start to get labor pains or their water breaks. Labor is a gradually progressive pain in abdomen, which starts to last longer and come more frequently with passing time. ‘Breaking of water’ is actually when the amniotic sac around the baby breaks and all the amniotic fluid comes out through the mothers vagina. In both these conditions, one should get to the hospital prepared for the child birth

If, however, these do not happen by the end of 41 weeks, your doctor may decide to induce labor and deliver your baby. So keeping in close contact with the doctor from 38 weeks on wards is important. This will help them monitor the baby’s health and plan a safe delivery

However, things may go wrong, so read about warning signs/red flags in pregnancy and tests and monitoring during pregnancy