The date that marks the beginning of your pregnancy is usually based on your last menstrual period. By the end of the first trimester (first 3 months) of pregnancy you will have experienced many physical changes. For your baby, the first trimester of gestation is a time of extremely rapid growth and development.

Your month 1

• The first changes are usually noticed during week 4 of your pregnancy.
  
  
• A metallic taste in your mouth might be your first—and only—real sign of the physical changes that are occurring.

Baby's month 1
By week 2 of gestation, the basic structures of the central nervous system have already begun to develop.

Your month 2

• By week 5, although you will have missed a menstrual period or have had 1 or 2 very light periods, you may feel as if you are just about to get your period. You may experience many of the feelings you normally get before your period—bloating, stuffiness, and headaches.
  
  
• Your breasts will begin to enlarge and to become tender.
  
  
• You will need to urinate more often than usual.
  
  
• In week 6, your vagina and outer labia will react to the increased blood flow by turning a bluish color.
  
  
• The nausea and vomiting of pregnancy often start now.
  
  
• By week 7, you may feel a bit dizzy sometimes and even short of breath.
  
  
• Small lumps may appear on your breasts, and the area around your nipples will become darker.
  
  
• By week 8, your hair may start to be less manageable.
  
  
• Vaginal discharges—clear, white, odorless—may start now.

Baby's month 2
By week 5, the embryo can be seen easily with the naked eye. By week 6, the heart is beating, and the head, chest, and abdomen are beginning to form. By week 7, indentations mark the sites where fingers and toes will form. By week 8, all of the internal organs are in place, and major joints such as shoulders and hips are quite obvious—despite the fact that the fetus is now only approximately 2.5 cm (1 in) in length.

Your month 3

• In week 9, you may notice changes in your skin. Also around this time your gums may begin to soften and need more care. For details, see Other Physical Changes.
  
  
• Your thyroid gland (at the side of the front of your neck) may become larger.
  
  
• By week 10, your uterus will have become the size of a grapefruit.
  
  
• Your breasts will have outgrown your usual bra size.
  
  
• By week 11, the nausea and vomiting of morning sickness may begin to disappear.
  
  
• Your blood volume will have increased a great deal, and you may have nosebleeds.
  
  
• By week 12, the end of the first trimester, your uterus will have risen above the pelvis and can be felt externally.

Baby's month 3
By week 9, a tiny mouth and nose are visible, and the limbs are growing rapidly. Week 10 is marked by clearly distinguishable fingers and toes, which are joined by webs of skin. By the end of week 11, every internal organ is formed and functional. By week 12—the end of the first trimester—eyelids are obvious, tiny fingernails and toenails are present, joints contract, and your developing baby can suck and swallow.

By the end of the first trimester, all of the systems of the body are well developed, and many organs are nearly complete. The fetus is not yet capable of living outside the womb, but it has certainly come a long way in 12 weeks.

First Month

Second Month

Third Month