Pregnancy Trimesters


Pregnancy is divided into three distinct trimesters. The pregnancy trimesters are characterized by specific changes and development in the mother and the baby. Find out what happens is each trimester.


Pregnancy Trimesters

A normal pregnancy usually lasts for 40 weeks though most first pregnancies might extend up to 42 weeks. For the convenience of medical observation and examination, pregnancy is divided into three distinct stages, commonly called as trimesters. The three trimesters mark important milestones in the progress of your pregnancy. Each trimester lasts for around 13 weeks, spanning the following pregnancy timelines

  • First Trimester – Weeks 1 to 13
  • Second Trimester – Weeks 14 to 27
  • Third Semester – Weeks 28 to 40

What happens in the First Trimester?

From a single cell to tiny body and limbs, your baby begins to grow rapidly in your womb during the first trimester. Strangely, in the first few weeks of your first trimester, you might not be aware that you are pregnant. 

Conception and Implantation

In the first week of your pregnancy, you’ll be surprised to hear that your baby isn’t even formed yet. Yes, your pregnancy theoretically begins on the first day of your last period even though you are not physiologically pregnant. In the next two weeks, you’ll ovulate and if a sperm manages to successfully reach your ovum, you’ll get pregnant. 

The single cell (zygote) that had formed after the sperm fertilized the ovum, undergoes cell divisions to become what is called a blastocyst. It is a ball of a few hundred cells which keeps growing tremendously. Most likely, you’ll have no idea at this stage about your pregnancy unless you have been closely following the early pregnancy signs. The growing embryo is planted in your uterus lining and by the end of week 4, you have missed your period. 

Pregnancy Tests and Confirmation

A home pregnancy test will soon show a positive result. In a prenatal appointment with your OB, you’ll be advised to take a pregnancy blood test and urine test to further confirm your pregnancy.

Morning Sickness

The implanted embryo puts your pregnancy hormones in action and you might begin to experience a few of the common pregnancy symptoms such as sore breasts, fatigue, frequent urination, and nausea. You can feel your food cravings and aversions take strange tastes as you try to visualize different kinds of foods to figure out what your taste buds are up to. Towards the end of the first trimester, the queasiness may seem to leave you slowly, while for some pregnant mothers, it can well last through the middle of the second or third trimesters as well. 

Embryo to Fetus

The blueprint of your baby’s organs is laid out and you can expect a rapid growth of your baby and also your body in the weeks that follow. Body organs undergo growth spurts inside your tiny baby. Your breasts too enlarge preparing your mammary glands for lactation. Your hips and waist see a change in shape as your uterus continues to bulge bigger. 

What happens in the Second Trimester?

While the first trimester began with the disbelief of carrying a life inside, with the start of the second trimester, you begin to sync well with your pregnancy. As the morning sickness eases away, you are energetic more than ever, you are hungry more than ever and you eat, more than ever now. This phase is often referred to as the ‘honeymoon’ period of pregnancy as you. aren’t as sick as you were in your first trimester and you wouldn’t be as heavier as you are going to be in the next trimester.

Baby’s organs and senses develop

Your baby has doubled in weight from what he or she was last week. Your baby is more like a baby now, wriggling and squirming inside all day. Your baby can listen to voices around now and his or her eyesight is at a rapid stage of development.

Pre-natal Tests

Between 15 to 20 weeks, your OB might schedule diagnostic tests. A multiple marker screening, popularly called as Triple screen test, is to check for any neural tube defects in the baby. If you opt for, amniocentesis may be scheduled to detect the chances of chromosomal abnormalities in the baby.

Baby Kicks and Baby Bump

Feeling your baby move is one of the exciting moments of pregnancy. At around week 18, most pregnant moms-to-be can feel their baby move or kick the belly. A baby bump can as well become apparent with the start of the second trimester. 

Rapid Changes and Development

Towards the end of the second trimester, your baby begins to breathe amniotic fluid.  Baby’s brain and eyes undergo active development. You might have leg cramps and feet swelling at this stage which are likely to last until childbirth. You may also begin to experience Braxton Hicks contractions sometime during the second trimester.

What happens in the Third Trimester?

You and your baby have undergone a huge metamorphosis and all that you want to happen as the third trimester sets in is hold your baby in your arms. The good news is that you are not too far as you have just one-third of your pregnancy left.

Huge and Heavy

With a big belly, sleeping discomforts can be common. There’s too much pressure to your bladder from above now and you can’t help yourself from frequent loo visits. Not to mention, the aches your body experiences are getting new and varied. Braxton Hicks can continue to get frequent. When baby drops down in the womb in the late third trimester, shortness of breath which has bothered you may ease up.

Kick Counting

Your OB may advise you to do kick counts. As long as you can feel your baby’s kicks 10 times in around two hours, she is doing fine inside. You may also experience increasingly stronger and closer Braxton Hicks contractions which sign that your body is preparing for the upcoming D-day. In the early third trimester, you shouldn’t get more than four contractions in an hour.

Baby is getting closer to the birth form

Baby’s eyelashes are grown and may flutter too. Baby begins to open and close the eyes. Baby’s brain continues to grow and the immune system develops steadily. A baby also begins to practice to master lung function by coordinating breathing with sucking and swallowing.

Except for the lungs and brain, most of your baby’s organs are almost developed. His lungs continue to mature and he might begin to shed vernix and lanugo, the white stuff off his body. Meconium (your baby’s first poo) is already in there inside her intestines and is not going to get out until she’s out. 

Contraction and Labor

In the last four weeks of the third trimester, you will visit your OB every week. Baby drops low in the womb with the head turned down. Around the time of true labor, the mucus plug which protected your cervix will gradually or suddenly get released in preparation for labor. Cervix will begin to dilate in a process which can last for a few hours or a few weeks. Labor contractions or water breaking is most often the first step in the birth process. 


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