We can see the earliest signs of pregnancy not long after conception occurs. Our body undergoes a remarkable change and will continue to change over the next 9 months. Hormones are responsible for these changes and for the very early pregnancy signs. The hormones are like little chemical messengers that run the show. Fluctuations in the hormones can cause an array of symptoms. Let's take a look at these and try to understand what's going on with the pregnancy hormone levels.

The hormones human chorionic gonadotropin (hCG), estrogen and progesterone will increase as the pregnancy progresses. The beginning of the increase early on will set about major changes in the body. The uterus and abdomen muscles will have to expand to take on the growing fetus. Early on you may feel cramping or pulling in the uterus. These are among the first signs of pregnancy.

Many women say that breast changes are one of the earliest signs of pregnancy. Breast changes will occur to nourish the baby after his birth. It's because they will enlarge as the milk-producing glands increase in size. You may see blue veins in the breasts and/or darkening of the areolas. The rising levels of estrogen and progesterone are responsible for these changes.

In early pregnancy the corpus luteum (the cyst that was formed when the egg popped from the ovary) will produce the tiny amounts of progesterone that will keep the uterine lining from shedding. Several weeks later the placenta will take over the production of progesterone that maintains the pregnancy.

The progesterone levels are ten times higher in a pregnant woman than in a non-pregnant woman. The progesterone is responsible also for preventing miscarriage. Low levels of this hormone can cause miscarriages and later in the pregnancy can cause preterm labor and/or premature birth. Progesterone helps the uterus to not contract and promotes the growth of blood vessels in the walls, which is essential for the baby's nourishment.

The key hormone in conception, estrogen, is also produced by the placenta. Estrogen that's responsible for the egg popping out of the ovary, and causing changes in the cervix, vagina, breasts and uterus to help bring about fertilization.

The number one hormone in pregnancy and the one that will give you a positive on a home pregnancy test is hCG - one of the most reliable of the pregnancy first signs. hCG is produced in small amounts by the placenta at first, increasing as the pregnancy progresses. hCG can be detected in both urine and blood. Many times a miscarriage can be diagnosed by seeing the falling hCG numbers in a blood test. This hormones keeps the body from rejecting the growing fetus. This hormone determines when to test for pregnancy and see a positive result.

So the earliest signs of pregnancy are a direct result of the hormones estrogen, progesterone and hCG. If the levels of these hormones fluctuate it can cause an array of problems including miscarriage, preterm labor, gestational diabetes and premature birth. The levels rise all through pregnancy then right before birth drastically drop. It's this drop that causes post partum depression, night sweats and mood swings.