Foetal Development: Week by Week

by Sam Malone


Each week in pregnancy chronicles the development of fetus and the dramatic changes that take place in both the mother and the child. Here is a quick overview of the 40 weeks of pregnancy.

  • Week One: In the first week of your pregnancy, your medical expert or obstetrician will start numbering from the first day of your last menstrual period just before pregnancy. Hence week one commences from the first day of your menstrual period. During this period, conception has not yet taken place, but the standard norm is to start counting your pregnancy week by week from this stage.
  • Week Two: In the second week, the baby has still not been conceived but the time is ripe for your body to start ovulating.
  • Week Three: In the third week, the sperm unites with the egg within the fallopian tube. Now that impregnation has occurred, the egg goes along on its way towards the womb, where it will be embedded in the uterus within the uterine lining.
  • Week Four: In the fourth week, the egg has arrived at the uterus and is now looking for a place to stabilize. You are now formally pregnant!
  • Week Five: In the fifth week, the body is hard at work in developing the baby; hence you might experience intense weariness.
  • Week Six: During the sixth week is when the baby's heart starts to beat, and is the most exciting time of the first trimester.
  • Week Seven: In the seventh week, the baby's size is just about half an inch.
  • Week Eight: In the eighth week, rapid development and growth is ongoing and various features start to appear.
  • Week Nine: In the ninth week, the baby that is growing rapidly now measures up to about an inch in length.
  • Week Ten: In the 10th week, you will be able to identify fingers and toes of the baby through a sonography.
  • Week Eleven: During the 11th week, the baby's head growth starts to slow down as it is almost as big as the rest of its body.
  • Week Twelve: In the 12th week, the gender characteristics of the baby begin to take shape.
  • Week Thirteen: The 13th week is the start of the second trimester and the baby might weigh approximately two ounces.
  • Week Fourteen: In the 14th week, the baby's neck begins to take shape and gets longer, while the hands start to function.
  • Week Fifteen: During the 15th week the baby starts to use its hands to a great extent and might even be sucking his/her thumb.
  • Week Sixteen: The 16th week is when the baby's bones start to harden. You will start needing an iron-rich diet, from here on.
  • Week Seventeen: In the 17th week most mothers start to recognize kicking sensations as the baby is now large enough to kick and move around.
  • Week Eighteen: In the 18th week, the baby weighs almost half a pound.
  • Week Nineteen: In the 19th week the baby's permanent teeth buds start to form behind the baby's milk-teeth buds.
  • Week Twenty: At the middle!: In the 20th of week you might experience some soreness or tenderness around the navel due to the pressure of the uterus pressing against it.
  • Week Twenty One: During the 21st week, some important growth phases start to slow down, but the baby's heart begins to grow stronger while the legs get longer.
  • Week Twenty Two: In the 22nd week, the baby is likely to weigh almost one pound!
  • Week Twenty Three: In the 23rd week, the baby starts to sport fingernails! During this particular week, the baby might have developed a surfactant, which is a substance that will help the baby's lungs to expand after birth.
  • Week Twenty Four: In the 24th week, the baby gains weight as it rapidly starts to gain fat and muscle on the body. During this stage rapid eye movement also commences.
  • Week Twenty Five: In the 25th week, several other important joints and ligaments develop, including the spinal joints and ligaments.
  • Week Twenty Six: In the 26th week, the baby has actively developed lungs, while the air sacs start to develop from this week onwards.
  • Week Twenty Seven: In the 27th week, the second trimester is complete as the baby's brain continues its' speedy rate of maturation.
  • Week Twenty Eight: The 28th week begins the start of the third trimester.
  • Week Twenty Nine: In the 29th week, the baby is likely to weigh almost three pounds while the head is proportionate to the rest of the body.
  • Week Thirty: In the 30th week, the baby's eyelids start to open and close while the bone marrow begins to produce red cells.
  • Week Thirty One: In the 31st week the baby is likely to weigh approximately 3 1/2 pounds!
  • Week Thirty Two: In the 32nd week the baby begins to gain weight speedily in the last few weeks due to an increase in the fat stores and muscle.
  • Week Thirty Three: In the 33rd week, the baby is likely to weigh approximately 4 and half pounds.
  • Week Thirty four: In the 34th week, the baby starts to take in a high quantity of fluid and, as a matter of fact, urinates almost a pint every day!
  • Week Thirty five: In the 35th week the baby is likely to weigh approximately 5 and half pounds!
  • Week Thirty Six: In the 36th week the baby is almost ready to be delivered!
  • Week Thirty Seven: At the end of the 37th week your gynecologist or obstetrician is likely to consider your baby to be full term!
  • Week Thirty Eight: By the 38 week, the development of the baby is almost complete and its principal job is to gain weight.
  • Week Thirty Nine: In the 39th week the average baby is likely to weigh approximately seven pounds!
  • Week Forty: The 40th week is considered to be the end of pregnancy, ready for delivery!

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