Growth and Development.
During pregnancy, the baby grows in the mother’s uterus, which is a muscular organ located between the bladder and the rectum. The lining of the uterus thickens and its blood vessels enlarge to nourish the growing baby. The placenta is the channel through which oxygen, nutrients, and other substances pass from mother to baby.

The process of growth and development has three phases called trimesters.
Weeks 0 through 13 are known as the first trimester. During the first trimester, growth and development in mother and fetus cause many changes to occur.

A woman may notice:

  • No period or a light period
  • Blue lines under the skin over her breasts and abdomen
  • Waistline expansion
  • Breasts that grow larger
  • Protruding nipples

Weeks 14 through 27 are known as the second trimester. During the second trimester, continuing growth and development in mother and fetus cause many changes to occur.

A woman may notice:

  • The abdomen begins to swell. By the end of the second trimester, the uterus is near the rib cage.
  • The skin on the abdomen and breasts stretches. Stretch marks may be visible.
  • Movements made by the fetus. Known as quickening, this often occurs sometime around weeks 16 to 20.
  • A dark line forming from the navel down to the middle of the abdomen
  • Brown, uneven marks on the face or other changes in skin pigment
  • Darkening of the area around the nipples

Often, the second trimester delivers a welcome energy boost to women and an end to morning sickness.

Weeks 28 through 40 are known as the third trimester. During the third trimester, continuing growth and development in mother and fetus cause many changes to occur.

A woman may notice:

  • Movements of the fetus can be felt more strongly
  • Abdominal pain that may or may not be true labor pains
  • Shortness of breath because the uterus is pushing against the diaphragm. The diaphragm is a flat, strong muscle that aids in breathing. Towards the end of the third trimester, the baby may drop down into a lower position. This will make it easier for the mother to breathe.
  • A need to urinate more often when the baby drops down into a lower position in the pelvis
  • Yellow, watery fluid leaking from her nipples, known as colustrum
  • Her navel sticking out

As the body readies for birth, a woman’s cervix begins to thin out and open.

During the third trimester, certain discomforts and mood changes may occur.