The process of pregnancy marks a pivotal change in the life of any new mother, both physically and mentally. Physically, you will be faced with some changes, ranging from swollen and tender breasts, fatigue and increased urination. Emotionally, you may be faced with rapidly changing moods, ranging from excitement and joy to anxiety and agitation. To ensure that you are well equipped to manage this, it is important that you research as much as is possible about the different stages that go into pregnancy, as well as what you can expect from each one.
Pregnancy is broken up into three distinct phases, or trimesters, across which foetal development can typically be mapped. Find out what each trimester holds for you and your newborn come through our week by week pregnancy calendar.
First Trimester:
- Week 1 & 2:
Conception typically occurs about two weeks after your last period begins. While calculating your due date, doctors count ahead by 40 weeks from the start of your last period.
- Week 3:
During this stage, you will begin ovulating, and one of your eggs will be released, travelling from your ovary into a fallopian tube. During the next 12 to 24 hours, your egg will be fertilised by a sperm that managed to penetrate it. During the next 10 to 30 hours, the sperm’s nucleus will merge with that of the egg. Over the next three to four days, the fertilised egg, or zygote, will move down into your uterus or womb, and also begin to form a cluster of cells, called the morula.
- Week 4:
By the time the rapidly dividing cluster of cells, now called a blastocyst, reaches your uterus, it will have split into two distinct sections. While the inner section will become the embryo, the outer section will begin burrowing into the lining of your uterus, so that your body can start nourishing it. This process is called implantation. In tandem, your placenta, which will nourish your baby during the months of pregnancy, has also begun to form.
- Week 5:
The fifth week begins the embryonic period, where your baby’s brain, spinal cord, heart and other organs begin to form. Comprising of three layers, the embryo’s top layer, called the ectoderm, will form your baby’s outermost layer of skin, central and peripheral nervous systems, as well as the eyes, the inner ears and other connective tissues. The middle layers, called the mesoderm, will form your baby’s heart and a primitive circulatory system. This layer will also form the basis of your baby’s bones, muscles, kidneys and much of the reproductive system. The inner layer, also called endoderm, will form a simple tube that is lined by mucous membranes. The lungs, intestine and bladder of your baby will begin developing here.
- Week 6:
This week marks a significant amount of growth for your baby. The neural tube along the back of your baby is closing, and your baby’s heart has begun to pump blood. The body begins to take a C-shaped curve and begins to form small buds that will become arms and legs. Rudimentary facial features have begun to form, with passageways that will eventually form into the inner ears and arches that will form the jaw also starting to take shape.
- Week 7:
At this stage, the brain and face of your baby begin to grow quickly. The arm buds that developed last week begin to take shape, forming into paddle-shaped appendages. Tiny nostrils, as well as eye lenses, begin to form.
- Week 8:
The eighth week sees your baby begin to form longer arms and legs, with fingers also beginning to form. The baby’s upper lip and nose also begin to form here. Your baby’s ears are also taking form, and the trunk of the body also begins to straighten.
- Week 9:
In this week, the arms of your baby grow, beginning to develop bones and
- Week 10:
By the tenth week, your baby’s head begins to take a more rounded shape, with the neck beginning to develop. The baby’s eyelids also begin to close to protect the developing eyes.
- Week 11:
In this week, your baby’s eyes are widely separated, with the eyelids fused and the ears being low set. Red blood cells begin to form in the liver, and by the end of this week, your baby’s external genitalia start developing either into a penis or a clitoris and labia majora.
- Week 12:
After twelve weeks of development, your baby’s face now takes on a human silhouette and begins to develop fingernails. By this week, your baby could be 2 inches long from crown to rump and weigh about 8 grams.
Second Trimester:
- Week 13:
At week 13, your baby’s intestines return to the abdomen from the umbilical cord. Your baby also begins to form urine and discharge it into the amniotic fluid. Tissues also develop around your baby’s head and within the arms and legs which will later become bone.
- Week 14:
By this week, your baby could be 3.5 inches long from crown to rump and weigh about 40 grams. His or her arms would have nearly reached the final relative lengths they’ll be at birth. The neck becomes more defined, and genitals begin forming. Red blood cells begin to form in the spleen.
- Week 15:
At 15 weeks, your baby begins to grow quickly. His or her skeleton is beginning to develop which you will be able to see during ultrasound scans in the coming weeks. Your baby’s scalp hair pattern also is forming.
- Week 16:
The interesting thing about week 16 is thatmake sucking motions with the mouth. Movements become more coordinated and are noticeable during ultrasound scans. By this week, your baby could be 4.5 inches long from crown to rump.
- Week 17:
At this week, your baby’s toenails begin to develop. Fat stores begin to develop under the skin. This fat will help provide energy and keep the baby warm after birth.
- Week 18:
By this week, your baby could be 5.5 inches long from crown to rump and weigh about 200 grams. During this week, the ears begin to stand out on either side of the head and may begin to hear.
- Week 19:
During this week, a greasy, cheese-like coating called vernix caseosa begins to cover your baby. This cover helps protect a baby’s fragile skin from abrasions, chipping and hardening that can result from exposure to amniotic fluid.
- Week 20:
At week 20 you are halfway into your pregnancy! During this week you could begin to feel your baby’s movements, which is an exciting experience for new mothers. By this week, your baby could be 6.3 inches long from crown to rump.
- Week 21:
By this week your baby is poised to gain more weight. He or she is becoming more active and would be able to swallow.
- Week 22:
During this week your baby is completely covered in lanugo – a fine, soft hair-like material. This lanugo helps hold the vernix caseosa on the skin. Your baby’s eyebrows may be visible. By this week, your baby could be 7.5 inches long from crown to rump and weigh about 460 grams.
- Week 23:
By this week, your baby’s skin is wrinkled, more translucent and would be pink to red in colour. He or she begins to have rapid eye movements, and the tongue begins to develop taste buds. Fingerprints and footprints also are forming. Your baby’s genitalia also develop further.
- Week 24:
By this week, your baby could be 8 inches long from crown to rump and weigh more than 630 grams. Your baby is regularly sleeping and waking now. He or she is also growing hair on the head.
- Week 25:
During this week your baby may respond to familiar sounds, such as your voice, with movement. Your baby’s hands and startle reflex are also developing.
- Week 26:
By this week, your baby could be 9 inches long from crown to rump and weigh nearly 820 grams.surfactant – a substance that allows the air sacs in the lungs to inflate. The surfactant also keeps the lungs from collapsing and sticking together when they deflate. By now your baby would have fingernails.
- Week 27:
Your baby continues to grow rapidly, and his or her lungs and nervous system continue to develop. The second trimester comes to an end after this week.
Third Trimester:
- Week 28:
By this week, your baby could be 10 inches long from crown to rump and weigh nearly 1 kg. Your baby’s eyelids are partially open and eyelashes form. He or she is steadily gaining weight which is smoothing out wrinkles on the skin.
- Week 29:
By this week your baby’s bones are fully developed. However, they’re still soft and pliable.
- Week 30:
By this week, your baby could be 10.5 inches long from crown to rump and weigh nearly 1.3 kg. Red blood cells begin forming in your baby’s bone marrow. His or her eyes would be wide open for a good part of the time. Your baby may have a good head of hair by now.
- Week 31:
By this week, your baby’s central nervous system has matured to the stage where it can control body temperature.
- Week 32:
By this week, your baby could be 11 inches long from crown to rump and weigh nearly 1.7 kg. His or her toenails are visible. Your baby practices breathing though the lungs are not yet fully formed. He or she begins absorbing vital minerals, such as iron and calcium from the intestinal tract. Your baby’s lanugo starts to fall off this week.
- Week 33:
During this week, your baby’s pupils can constrict, dilate and detect light entering his or her eyes.
- Week 34:
By this week, your baby could be 12 inches long from crown to rump. Your baby’s fingernails would have reached his or her fingertips. The vernix caseosa begins to get thicker.
- Week 35:
This week onwards your baby begins to gain weight rapidly; about 230 grams a week for the next one month. His or her limbs begin to get chubby.
- Week 36:
By this week, your baby would take up most of your amniotic sac giving him or her less space to move around. You should keep a tab on baby movements and make sure that he or she is active.
- Week 37:
By this week, your baby’s organs are ready to function on their own. To prepare for birth, your baby’s head might start descending into your pelvis.
- Week 38:
By this week, your baby has shed most or all of the lanugo. His or her toenails would have reached the tips of toes. His or her brain might weigh about 400 grams. Your baby is developing a firm grasp.
- Week 39:
During this week, your baby’s chest becomes more prominent. For boys, the testes continue to descend into the scrotum. He or she is being supplied antibodies by the placenta to fight infections post birth.
- Week 40:
This is the week your pregnancy comes to an end, and you are ready to deliver your baby. By this week, your baby could be 18-20 inches long and weigh 2.9 kg or more.
