Have you ever heard of a pregnancy calendar? A pregnancy calendar is simply a record of all the changes a woman and her baby will go through during the 40 weeks of pregnancy. Many expectant parents spend countless hours going over the pregnancy calendar so they can monitor what is going on inside the mother's body at any given moment. While the changes the mother is going through are very evident by the changes in her body outwardly, the changes the baby is going inside the mother's womb are not evident. That is why having a pregnancy calendar is so useful. Expectant parents can look at a pregnancy calendar to know what stage of development their unborn baby is in at any given week. Here is a general rundown on what you find on a pregnancy calendar.

Week 1-4: Conception occurs and the egg is fertilized.

Week 5-8: Your baby's heart has begun to beat by the 6th week. You baby has arms and legs have started to develop by week 8.

Week 9-12: By the 10th week your baby will be moving around inside of your womb. You probably do not feel it, but he or she is moving.

Week 13-16: During the 13-14th week a doctor may be able to determine the sex of your baby through an ultrasound. Your baby's heartbeat can also be heard during this time. Your baby's bones begin to harden during this time and you may begin to notice it when he or she moves around in your womb. Babies at this age can suck his or her thumb.

Week 17-20: Your baby's organs are developing and the sex of your baby can positively be identified. Your baby's body starts to be covered with fine hair.

Week 21-24: Your baby will start to deposit fat on his or her body so that he or she can deal with changes in temperature during and after birth.

Week 24-28: Your baby is able to hear sounds and can sense darkness and lightness. This is the time when the baby's movements start to lesson because the uterus is becoming crowded.

Week 29-32: Your baby's eyes begin to move. The size of your baby's head is starting to catch up with the size of his or her body. Your baby's brain is growing very fast. All major organs are developed by the 32nd week, except the lungs.

Week 33-36: Your baby starts to open and close his or her eyes during this stage. Your baby's fingernails start to grow long.

Week 37-40: Your baby's lungs start to get ready for birth. You can go into labor at anytime during this stage.

These are just the highlights of what you would see on a pregnancy calendar. If you are pregnant, you are encouraged to get a pregnancy calendar of your own to chart your baby's development. These calendars can be as simple or as detailed as you would like them to be. You can even locate pregnancy calendars that have room for you to write important details down for each week. This is a great way for you to monitor yourself and your baby. Pregnancy calendars are a great thing to have for a keepsake that you can give to your child when he or she is grown along with their baby book.