Baby growth starts, when the ball of cells attaches to the lining of the uterus by the process called implantation.                                                                       

   This process starts after 6-7 days of fertilization and it takes about 3-4 days to be completed. It’s a time of great anticipation and a series of changes occur in your body and the fetus. Here we will discuss the changes that occur in a fetus in a little detail. 

Changes that occur in the fetus during the first phase: 

         During the first 3 months of pregnancy, your baby changes from a fertilized egg to a fully formed fetus. All the major organs and systems of the body are getting shaped so you need to be very careful with the protection of the baby. 

•    The fertilized egg becomes a cluster of cells that implants in your uterus. The placenta and the amniotic sac (filled with fluid) all start to grow. 

• The nervous system of baby changes from a simple tube to a developed brain and spinal cord. Nerves and muscles of the body start working together baby can start moving but it is so early for you to feel. 
• The heart takes its original shape and begins to beat you can hear this beat in ultrasound as early as week 8. It beats normally 120-160 times every minute. 
• The baby develops the digestive system with the kidneys and intestines. 
• Lungs and other major organs are also formed but are not working so properly. 
• A soft skeleton is fully formed and it starts to grow. 

• The baby starts to look like a baby because the external structure is formed. Now the baby has arms, legs, fingers, and toes. His face gets eyes, ears, a nose, and a mouth.  
• Genital or sex organs also start to grow but it is too early to judge by ultrasound whether you will have a baby girl or a baby boy. By the end of the first three months, the baby will be only 2-3 inches long. 

Conclusion; 

 In this paragraph, I explained all the physical changes that happened in the growth and development of the baby. the heartbeat of the baby and fetus become in the baby shape in the last of the first trimester. 

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