The growth of a foetus in the womb is truly amazing; it is a miracle in itself. Every week, your baby is changing and growing. The initial stage of pregnancy, being the first three weeks, is when conception occurs, and the embryo attaches itself to the uterus. The placenta originates at this time also. You can keep track of how your baby is developing week by week. This way, you know what parts of the body he is developing at certain times.
During this time, your baby will start to develop organs, such as the brain and heart; his spinal cord will also start to form. The heart starts to do its pumping work around week five. He now has a stomach, and he is starting to get eyes and ears.
In his sixth week, his heart will develop its chambers, two atria and two ventricles. Cosmetically, the baby also has the beginnings of an upper lip.
The rest of the first trimester is full of growth and new developments, beginning with the formation of the umbilical cord, which coming from the placenta, helps to nurture and sustain your baby throughout the pregnancy. The arms and legs are becoming more apparent, as are fingers and toes. The baby is starting to look like a baby. At week nine, and at just an inch in size, your baby starts to be able to move. The baby's skeleton starts to develop around week 10. He started to get his reproductive organs back in week nine, but week 11 is when his gender is obvious. By the end of week 12, your baby has grown to 3 inches in size.
Week 13 starts the beginning of your second trimester. Your baby starts to kick at week 13, and at week 14, his hormones are starting to activate. His skin starts to develop during this period, starting out very thin. By your 16th week into pregnancy, your baby may be able to make certain faces, and he has grown to approximately 5 inches in size. He is also able to form a fist.
As the second trimester goes on, so too does your baby's growth. He will start to gain some fat, which will be needed after birth. During this time, he can also start to hear you; it may be sort of muffled, but he can hear you, as well as other things going on around you. His kidneys are also working, and his skin is becoming stronger and thicker. He may even start to get hair during this time. His arms and legs are developed fully.
During this last stretch of the second trimester, many changes take place. The baby's blood cells begin to be produced by the bone marrow. He can taste and feel now. His lungs are also developing and getting ready, and he begins the process of breathing. His bones have also become hard and provide stability. He is definitely moving all around in there, depending on when he is awake and when he is sleeping.
The rest of the pregnancy, known as the third trimester, is a whirlwind with checkups and preparing for the arrival of your baby. His nervous system starts to work, and his brain is still developing very quickly over this time. He can also open his eyes now. His respiratory system continues to work, and it is preparing for life after birth. His moving around may keep you up at night, but make sure to feel for his movements every day. He is really growing at this time, adding on weight. The baby can grab onto something and hold on, and he also has a good sucking reflex.
During this last part of the third trimester, your baby is finally ready to be born; his lungs have fully developed, his immune system is functioning, his brain is at work, and he has probably grown to approximately 2.72 to 3.63 Kilogram, if not larger.
It's important for you to be aware of all of the changes going on inside your body and with your baby. As his brain is developing, it is especially important for you to practice good nutrition and take a prenatal vitamin every day, according to your doctor's orders. Get plenty of rest, and take care of yourself because you have another person to think about now. Especially stay away from cigarettes, alcohol and drugs while pregnant. These can cause significant problems for your baby.