During pregnancy, the fetus grows inside the mother’s abdomen. There it is surrounded by the so-called amniotic sac, which protects it. It bursts under the birthing process.
What is the amniotic sac?
The amniotic sac is a bag of tissue. It serves as a protective space for the growing fetus in the womb. By the eighth week, the embryo is forming, which is medically called embryogenesis. This period, called the embryonic period, includes fertilization of the egg through implantation in the lining of the uterus to the development of the anlagen for the organs. From the third month of pregnancy, called fetogenesis, the amniotic sac develops through an unfolding of the middle and outer germ layers. It consists of two skins called the amnion and chorion. These skins are two thin but very stable membranes. They grow with the fetus until birth, giving it its own space in which to develop. This space is filled with amniotic fluid. This serves to prevent the tissue of the amniotic sac from growing together with the developing embryo and later the fetus. Until birth, the amniotic fluid has a volume of about one to 1.5 liters. During delivery, the amniotic sac ruptures and the amniotic fluid leaks out.
Anatomy and structure
The amniotic sac forms from two membranes beginning in the eighth week of pregnancy. The inner membrane is called the amnion. It surrounds the amniotic fluid and the fetus. The outer one is called the chorion. It is part of the placenta and connected to it by the umbilical cord. The exchange with the mother takes place through the chorion. The amniotic sac has no vessels. It is very thin, but extremely durable. The amniotic fluid is a clear liquid consisting of water, potassium, sodium, proteins, fat and glucose. It completely surrounds the fetus and is formed on the inner wall of the amnion. As the pregnancy progresses and the baby develops, the proportion of other substances in the amniotic fluid increases. For example, the fetus loses hair and skin scales. Therefore, it is renewed every three hours. From the twelfth week, the fetus begins to drink the amniotic fluid. In this way, he trains the lungs and digestive system. Thus, the child releases the first urine already in the womb.
Tasks and functions
The functions of the amniotic sac can be summarized as a protective membrane for the fetus. It absorbs shocks from the fetus and from outside. At the same time, it protects against noise, which reaches it only in a muffled manner. It is also a barrier to invading germs. Thus, it is supposed to protect against infections. Another task of the amniotic sac is the exchange of amniotic fluid and the removal of harmful substances. As the pregnancy progresses, the amount of amniotic fluid also increases so that the fetus continues to be completely surrounded by the fluid. Thus, the amniotic sac provides for the increase in production no later than the 15th week of pregnancy. As the fetus begins to drink the amniotic fluid, an increase in the amount of water is essential. An important and its last function is performed by the amniotic sac at birth. If it bursts, it sets the start signal for the delivery. In the normal case, the rupture of the membranes is spontaneous. It occurs in conjunction with labor pains and can happen at different times. If it occurs before labor, doctors call it premature rupture of the membranes. If it happens at the beginning, it is categorized as premature. If it goes off at the end of the opening phase, it is timely. It is classified as late if it remains intact until the expulsion phase or even survives the birth. In addition, to speed up the birth process, in some cases it is advised to burst the amniotic sac. This is called bubble bursting. The color of the amniotic fluid also provides an indication of whether the baby is overripe. If it is green in color, delivery is induced so as not to endanger either the baby or the mother.
Diseases and ailments
The amniotic sac usually does not open until the baby is born. It becomes problematic when premature rupture of the membranes occurs. This happens when the amnion ruptures. Depending on the timing, it can pose a risk to the pregnancy. It is often caused by an infection in the woman’s genital area that travels to the uterus. In half of the cases, the birth of the child takes place within the 48 following hours after the rupture of the amniotic sac.A complication of the loss of amniotic fluid is a higher susceptibility to infections. Depending on the week of pregnancy, the fetus may develop malformations of the lungs. In addition, the freedom of movement for him is limited. The greatest risk is that of miscarriage or premature birth if labor is induced. Chorioamnionitis, which has the medical term, is an inflammation of the membrane of the amniotic sac that can spread to the amniotic fluid. Its incidence is low, at one to five percent of all pregnancies. It is caused when bacteria from the mother’s rectum enter the vagina and reach the amniotic sac. If it occurs, it can not only lead to premature birth or miscarriage of the baby, but also cause blood poisoning in the mother.
