Pregnancy is a beautiful journey loaded with miracles that unfold every week. From conception to birth, changes take place week by week, physically and mentally. Pregnancy week by week are transformations seen within the mother’s body and the developing fetus. Each week brings along new signs, symptoms, growth, and developments. The whole gestation period is calculated as 40 weeks and begins from the day you had your last menstrual period.
Pregnancy is divided into three trimesters, each lasting three months. The first trimester spans conception to 12 weeks of pregnancy. The second trimester covers weeks 13 to 27, and the third from weeks 28 to 40. While the average gestation length is 40 weeks, it can vary from one pregnancy to another. For some women, the gestation period may range from 37 to 42 weeks, and babies born during this time are full-term (1).
During the first trimester of pregnancy, in the first month, from weeks one to four, several significant changes occur. This phase marks the fusion of cells, fertilization, hormonal releases, and your body’s preparation for the baby. The phase is referred to as the ‘getting ready’ stage. This is also when you may experience uncomfortable symptoms, such as nausea and fatigue. The growth increases during the second month, from week five to eight. The nervous system starts forming tiny buds or arms and legs, and the little heart initiates its beats. By the eighth week, all major organs and body systems start developing, and the fetus size resembles a black bean.
In the third month, from week nine to week 12, the teeth and taste buds begin to form. The arm, hands, and fingers are fully formed at this stage. Organs, muscles, and bones continue developing, and the digestive and circulatory systems become functional. The size of the developing fetus will be that of a plum. Passing the first trimester brings relief as the most significant development has occurred, and the chances of miscarriage also get considerably less.
The second trimester is an exciting phase as you can discover the gender of your baby. There are some more precious developments spanning four months, from weeks 13 to 16. Now you can hear the baby’s heartbeat clearly, while the vocal cord and lungs begin to develop. The skin starts to thicken, and the external genital organs are fully formed. In the fifth month, from weeks 17 to 20, most women can sense kicks and punches of the baby. The baby’s skin is covered in peach fuzz at this stage, and distinctive fingerprints take shape.
In the sixth month, spanning weeks 21 to 24, the baby’s eyelids begin to part and it responds to sounds by gentle movements. Limbs take shape and are coordinated. The bone marrow helps form blood cells, and the lungs complete their development. The seventh month is the last month of the second trimester, from weeks 25 to 28. Now the baby is maturing and growing faster. There is more body fat at this stage, and melanin forms, giving the baby color. The baby will now have the ability to turn their head around (2).
The third trimester marks the final stage of pregnancy and is the most fascinating period as you are close to meeting your baby. This trimester spans from week 29 to week 40. In the eighth month, from week 29 to week 32, the fetus' lungs and brain develop, enabling it to process more information. The kicks become more prominent, and other major organs are fully formed. In the ninth month, from week 33 to week 36, the bones grow stronger, and the lungs mature. The fetus loses its body hair and hair on the head.
The tenth month is the final month of the trimester, from week 37 to week 40. You are ready to deliver the baby at any time. The fetus has now changed its position and is mainly head-down in the uterus. At this stage, you might feel contractions, prompting the requirement of your family, doctors, and midwife as the time to meet your baby arrives (3). Although your pregnancy ends with the third trimester, more joyous moments await you and your magical baby.
Some people experience no pregnancy changes at week one, while others may experience breast tenderness, fatigue, and cramping symptoms. A woman is not pregnant at week one since the pregnancy is usually calculated from day one of the last menstrual period. It can only help estimate the due date. The actual pregnancy will start when you miss your periods at the end of week four (4).
At the 20th week of pregnancy, the baby is active and can kick, punch and turn around. Its skin is covered by a white, greasy substance called vernix, helping prevent the skin from drying. The baby also develops the sucking reflex (5).
At this stage, the baby is referred to as full-term, which means the baby is mature enough to survive outside the mother’s womb. However, you may still have to wait a few weeks before giving birth (6).
During the last weeks of pregnancy, you may experience swelling, tingling, and numbness in your hands and legs. You can also experience heartburn, hemorrhoids, and varicose veins. These conditions are normal to occur in the last weeks of pregnancy, and they usually resolve soon after child-birth (7)
A birth is referred to as premature, when the baby is born before 37 weeks of pregnancy (8).
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