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This page and the pages associated with it, provide basic information about pregnancy. It is only intended to be source of basic information and should never be used as a guide to self diagnosis or self treatment. We will discuss the basic changes , the common complaints and the more serious complications of pregnancy. Please refer to Fertilization and Early Pregnancy and Implantation .

Implantation is complete at the time of onset of the next expected menstruation. The next menstruation will not occur ( unless there is implantation bleeding, but this occurs very seldom).

As soon as implantation occurred the pregnancy must prevent menstruation to occur . If the inner part of the endometrium is discarded , it will be the end of the early pregnancy. ( See Implantation ). The early pregnancy prevents menstruation by secreting a hormone called hCG (humanChorionicGonadotrophin). See hCG and the Glossary page. This hormone (hCG) stimulates the corpus luteum. The corpus luteum grows bigger and produced more progesterone and oestrogen. The higher progesterone levels causes the changes in the endometrium to continue. The glands secrete more protein and the spiral arteries become bigger. The endometrium growths thicker and it is no referred to as a decidua. ( Decidua is the scientific name of a endometrium supporting a pregnancy.) Progesterone has a side effect. It has the same effect on the brain as some sleeping tablets. This is the reason for the tiredness and drowsiness experienced during early pregnancy. The high levels of estrogen ( also produced by the corpus luteum) causes breast stimulation and is the reason for the tender breasts and nipples. The oestrogen and progesterone levels are higher than they ever were during the non pregnant state.

The high progesterone levels decreases the tone of non voluntary muscles. These muscles relax. The bowel muscles ( also involuntary muscles) also relax. The bowel contains gas and as the muscle tone decreases the gas causes bowel distention. A feeling of bloating is thus very common in pregnancy . ( long before the the pregnancy itself is palpable).

As the embryo and placenta grow bigger the womb must enlarge to accommodate the pregnancy. The enlarged womb pushes against the bladder . This is the reason why pregnant women need the bathroom more often.

Graphic Presentation of Early Pregnancy
This drawing shows the pregnancy at the completion of implantation. The purple ball represent the embryo and the yellow outer part represent the chorine. The chorine will develop into the placenta. Its function is to supply the embryo with oxygen and nutrients and remove the embryo's waste products. (refer to Implantation and Early Pregnancy).

Compare it with the next drawing. The next drawing shows what would happen if the corpus luteum stopped functioning. Menstruation will start and the inner two thirds of the endometrium will be discarded with the early pregnancy.

This drawing illustrates the effect of human Chorionic Gonadotrophin (hCG) on the corpus luteum. It stimulates the corpus luteum to produce more progesterone and to grow bigger. Normally in the absence of hCG the corpus luteum will stop functioning after ten days and menstruation will begin.

All pregnancy tests (blood or urine) detect the presence of hCG. If hCG is detected the pregnancy test is positive. hCG is present only in pregnant women.