Your unborn baby does not breathe through her mouth and nose while she is in the womb. Until her exit from the womb, your baby develops in an environment filled with amniotic fluid.

At 37 weeks, a pregnancy is full term--if the baby is born now, it will not be premature. Ideally, however, the pregnancy will continue until 40 weeks. This final stage of the pregnancy may be difficult. The cumulative weight gain may make the mother uncomfortable, even while sitting or lying down.

The first trimester of pregnancy lasts from fertilization to the 13th week. During this time the embryo will implant, form the fetal part of the placenta and develop all its organs. Your body will pump out hormones and produce more blood cells to support the pregnancy.

The third trimester of pregnancy lasts from week 28 until delivery. During this time the baby is growing and gaining weight rapidly. There are many physical and emotional experiences that occur during the last months of pregnancy.

When you are 14 weeks pregnant, you have just completed your first trimester. While more miscarriages occur in the first trimester than at any other time, pregnancy complications can still develop after this time.

At the end of your 13th week of pregnancy you are at the beginning of your second trimester. Your baby is almost 3 inches long and weighs almost an ounce, according to Baby Center. It is important to realize that not all women experience the same symptoms at the same time.

Week 6 of pregnancy is considered early pregnancy and is about halfway through the first trimester. Some women find out they are pregnant around this time. Babies at this stage can be measured with an ultrasound, although many details may be difficult to see.

At seven months (28 weeks) into your pregnancy, you are in the first week of your third trimester and about 12 weeks from your due date. By this week, your baby weighs 2 1/4 pounds (about the size of a Chinese cabbage) and measures 14.8 inches from the top of her head to her heels, reports BabyCenter.

For many women anxious to find out if they are pregnant, waiting until a positive pregnancy test is possible is just unbearable. Although many signs of pregnancy do not appear until weeks after conception, there are a few signs that can occur as soon as a week after conception in some women.

The first trimester, or three months, of pregnancy, can present many risks to the developing fetus. Because organs, facial features, skeletal tissue and limbs are developing at this time, any negative affect on the fetus can result in serious birth defects.

During the first trimester (or first three months) of pregnancy, changing hormone levels begin to transform a woman’s body in ways that help to support the growing fetus and physically prepare the mother for childbirth.

Although many women in the first trimester of pregnancy want to eat as healthy as possible, morning sickness can make it difficult to keep those healthy foods in their stomachs long enough to be digested.