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A pregnancy is divided into trimesters: the first trimester is from week 1 to the end of week 12. The first trimester begins on the first day of your last period and lasts until the end of week 12. This means that by the time you know for sure you’re pregnant; you might already be five or six weeks pregnant! A lot happens during these first three months.

Physiological changes happen in pregnancy in order to develop the fetus and to prepare the mother’s body for labor and delivery. Most of the changes are normal and some of them may even mimic a disease. It is important to distinguish between the two. Many changes that women experiences during this period might be confined only to the duration of being pregnant, which might make her uncomfortable at times. But the entire body undergoes innumerable changes in order to make it hospitable.

Here are major changes that the body undergoes in the first trimester.

Week 1- 3:

For now, it may seem that nothing is happening on the outside. If the fertilization has been successful between your egg and your partner’s sperm, the resulting zygote is now turning into a blastocyst and is heading towards the uterus to transform into a complete human.

Hormones called, estrogen and progesterone are being produced in order to nourish the young one until the placenta takes charge. Simultaneously, the blastocyst attaches to the uterus (after 1 week of fertilization approximately) and the placenta starts to take shape, and begins producing hCG, (which can be picked up in urine to confirm pregnancy).

Sense of smell: A heightened sense of smell is the real side of pregnancy caused by estrogen and hCG. The same is also responsible for morning sickness.

By this time, your little one can be compared to the size of a vanilla bean. Yay!

Week 4-6:

 By the starting of week 4, many women may start experiencing morning sickness, that mimics PMS including nausea, vomiting, breast tenderness, backache, mood swings, bloating, cramping, etc. Some of them might experience nothing except missed periods. Implantation leads to the production of hCG which keeps on the release of estrogen and progesterone continuous which helps in inhibiting shedding of the uterus lining.

By week 5, It’s this time when you can get a pregnancy test done. You may now announce this big news to your loved ones.

Following the next week, you may have to go to the loo for urination more than usual, because of increased blood flow, and your kidneys are getting more efficient in removing wastes from the body.  Also, your growing uterus puts pressure on your bladder, leaving less space for urine storage.

Along with this, you might experience heartburn and indigestion, as your gastric muscles slow down in order to absorb optimum nutrients from everything you eat.

By now your baby is as big as a poppy seed. (That’s still too tiny).

Week 7-9:

By this time, you may now clearly notice your ever-growing breasts, this is because your breasts are now depositing fats and have got increased blood flow. The areola may also seem darker than ever. They may even hurt when you touch. This all is happening to prepare your body for breastfeeding in the months to come. Coping up with morning sickness might be a habit by now, but another thing that is waiting around the corner is exhaustion. You might feel as if you are out of energy throughout the day. But don’t worry, this is all going to go in the coming weeks.

Your baby is now as big as a raspberry.

Week 10-12:  

Some moms may still feel the symptoms and may even experience constipation due to reduced bowel movements. The fiber in the diet and adequate fluids may help relieve it. Some of you might even start seeing your veins more clearly under the skin that is because your blood volume, increases nearly almost by 50% and veins have to cope up with the flow. You might also see a little bump by the grace of your growing uterus.

By week 11, you might be feeling a lot hungrier than ever, that’s because your body is gearing up to get accustomed to increased nutrient demands. Your ever-growing uterus is now putting pressure on your stomach and putting your intestine in distress which may result in bloating, burping, and passing gas. This might make you feel uncomfortable, but hey! It’s all for your baby’s comfortable stay.

All this time, it’s not only your baby that is being formed but also the placenta. Once it is formed, your body will adjust to the system and your fatigue may kick-off.

By week 12, that’s the last week of 1st trimester, your blood vessels widen up and relax (all thanks to progesterone) increasing the blood flow to the baby, but slowing the return of blood to you, causing a little dizziness, this might also occur due to low sugar levels if you are not eating enough.

By the end of 1st out of 3 trimesters, your baby is as big as a lime. Congratulations!


M. Sc. Gold Medalist

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