How does your baby grow

By Smriti Daniel

It takes 40 weeks inside the womb for a single cell to turn into a baby – 40 weeks of growing fingers, toes, heart and lungs, skin and bones. When will your baby begin to move? When will he or she be able to hear your voice?

When will you know whether it’s a boy or a girl? This week, Dr. Nalinda Rodrigo, Consultant Obstetrician and Gynaecologist, takes us through the development of a foetus, pointing out some of the most crucial milestones.

First Trimester:

Week 2: A doctor will count the days of your pregnancy from your last period, but at two weeks you are not actually pregnant. Instead your body is preparing itself – it will release an egg that will eventually make its way down the fallopian tube. “The fertilization typically happens around the 14th day,” says Dr. Rodrigo, explaining that this is in the middle of the average 28 day cycle. When the egg meets the sperm fertilization takes place. The fertilized egg, now known as a zygote, will take three to four days to finish its journey down the fallopian tube – ending up in the safety of the uterus.

Week 4: The tiny zygote has now gathered cell mass and is now known as a blastocyst, says Dr. Rodrigo. It has made itself at home – implanting itself into the rich, nurturing lining of your uterus. As the blastocyst grows it turns into an embryo. After implantation, the embryo divides itself into two parts: one will become the placenta, while the other becomes the foetus. Pointing out to the availability of very sensitive blood and urine tests, Dr. Rodrigo says that by the end of this week you may be celebrating a positive pregnancy test.

Week 5: The fifth week marks the beginning of the embryonic period and now your embryo is made of three layers. The outermost is the ectoderm and out of it will form your baby’s top layer of skin, central and peripheral nervous systems, eyes, inner ear, and many connective tissues.

Out of the middle layer of cells – known as the mesoderm - will come your baby’s heart and circulatory system. This layer of cells will also develop into your baby’s bones, muscles, kidneys and much of the reproductive system. The remaining inner layer - the endoderm - will become a simple tube lined with mucous membranes. Inside it, your baby’s lungs, intestines and bladder will develop.

Week 6: During the sixth week of your pregnancy, red blood cells have begun forming in your baby’s spleen. Your baby’s heart will begin to beat and blood will start to circulate throughout his or her body. The amounts of blood the tiny heart can hold are miniscule, says Dr. Rodrigo, estimating that there may be as little as 1/50 or 1/100 of a drop of blood in the heart. Sensitive ultrasounds introduced through the vagina are nevertheless sensitive enough to pick this up. His/her umbilical cord will also start to form, as will his/her head, eyes, intestines and liver.

Week 8: Eight weeks into your pregnancy, or six weeks after conception, your baby’s arms and legs are growing steadily longer, and fingers have begun to form. The delicate shell-shaped parts of your baby’s ears are becoming visible, as are his or her eyes. The upper lip and nose have formed. As for the body, the trunk is beginning to straighten, giving your baby more length.

By the end of this week, your baby may be about 1/2 inch long. Week 10: Congratulations! Your baby has now earned the title of foetus and is no longer an embryo. This week marks the end of the embryonic stage of development. Your baby’s external genitalia begin to form this week while his/her facial features as well as limbs become more apparent. By the end of the week, your baby’s vital organs will not only be formed but will also have begun to work. According to Dr. Rodrigo, the baby may begin to move this week, but it will be a few weeks before you can feel it.

Second Trimester:

Week 14:Now that you are 14 weeks pregnant, you have officially started your second trimester. “The risk of miscarriage is significantly decreased at this point,” says Dr. Rodrigo adding that morning sickness will also have subsided in most mothers. Your baby’s arms have almost reached the length they’ll be at birth and your baby’s neck is slowly becoming more defined. The baby’s reproductive organs continue to develop, as the baby begins to grow some hair as well as form eyelids, fingernails and toenails.

Week 18: Since the toe pads and finger pads are formed, fingerprints aren’t too far behind. “The baby’s nails have come up to the edge of their fingers,” says Dr. Rodrigo, explaining that later they will overgrow. Still, the most exciting development is that 18 weeks into your pregnancy, or 16 weeks after conception, your baby’s ears have begun to function. Standing out from the sides of his or her head, the ears and nerve endings have become “hooked up” and the brain is now receiving auditory information.

Your baby is now lulled by the steady beat of your heart and twitches in response to your stomach rumbling and your blood rushing through your veins. Though cocooned from the external world, he or she may even be startled by loud noises. Your baby’s sex will become apparent this week or in the coming weeks.

At this point, your baby may be 5 1/2 inches long from crown to rump and weigh 200 grams.

Week 22: Your baby’s sense are so developed by the time you are 22 weeks pregnant that he/she is likely to start experimenting. An ultrasound might reveal the baby sucking on his or thumb, for instance. The brain’s development is progressing rapidly and the baby’s sweat glands have also begin to develop.

“The baby is now completely covered with a fine, down-like hair called lanugo,” says Dr. Rodrigo. The lanugo helps hold the vernix caseosa on the skin. This white cheesy substance will cover and protect the skin of the foetus right up until birth. By now your baby may be 7 1/2 inches long from crown to rump and weigh 460 grams.

Week 23: By week 23, there is a decided thickening of the skin, says Dr. Rodrigo. This week your baby begins to have rapid eye movements and his or her tongue will soon develop taste buds. In boys, the testes are beginning to descend from the abdomen. In girls, the uterus and ovaries are fully formed –already stocked with her lifetime’s supply of eggs.

Week 26: Should an emergency lead to an early delivery, the chances are that with good neonatal care and proper facilities the child can survive, says Dr. Rodrigo, explaining that he or she has put on weight and now comes in about 600 grams.

Third Trimester:

Week 28: At this point in your pregnancy, your baby’s weight gain has begun to fill out the many wrinkles of skin that covered his or her body. The baby’s eyelids are partially open, complete with delicate eyelashes.

By now your baby may be nearly 10 inches long from crown to rump and weigh nearly 1,000 grams. The good news is that generally healthy babies born this week have a 90 percent chance of survival without physical or neurological impairment — and these odds only get better with every additional week he or she stays in your womb.

Week 28: By week 28, you should be able to sense some regular movement during the daytime. “Keep a mental count of the baby’s movements, there should be a minimum 10 movements during daytime or one every hour,” says Dr. Rodrigo, advising patients to contact their doctor if the baby seems to be decreasing its activity.

Week 30: “Your baby’s lungs are maturing,” says Dr. Rodrigo, adding that in about two weeks they will have completely matured. As your baby begins practising how to breathe, he or she may end up with a case of the hiccups – the result of gulping down too much amniotic fluid. Your baby has also begun to prepare for her entry into the world by layering on some body fat – something that will keep her warm when she is born.

He/ she weighs about 1.2 kilograms right now.

Week 36: Thirty-six weeks into your pregnancy, or 34 weeks after conception, your baby is gaining weight rapidly — approximately 227 grams a week for the next month. This is of course provided maternal nourishment is up to mark, cautions Dr. Rodrigo.

It’s a snug fit inside your womb, and your baby can no longer draw his or her fists back for a nice punch or move his or her feet for a proper kick. Instead expect lots of stretches, rolls and wiggles, says Dr. Rodrigo. He adds that the baby will soon move into its “final position” – preparing to be born, the baby must descend into the head-down position.

Week 40: This is the official end of the gestational period. Even though your baby is ready and able to live outside of you, it is perfectly normal for your baby to arrive as much as two weeks before or after the due date.

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