The amniotic sac

The amniotic sac is one of the most important structures that surrounds the fetus. It is filled with a liquid that envelops the baby during the nine months. It is the child’s “home”, his gym and his main protection from knocks, bumps and other external pressures.

It allows the fetus ample space to swim and move around, and in this way helps it build its muscle tone.

In order to keep the baby in a welcoming environment, the sac and the amniotic fluid it contains have a slightly higher temperature than that of the mother’s body, usually 37.6°C.

In this bag, there are about 30 ml of amniotic fluid in the 10th week of pregnancy .
This liquid has its peak around weeks 34 – 36 reaching about 1 liter in volume.

When we talk about water breaking, we are referring to this sac which tears releasing the amniotic fluid contained in it which then begins to flow out through the cervix and vagina. Water usually breaks around the end of the first stage of labor.

Identical twins (monozygotic or monovular twins) often share the same placenta, but usually have amniotic sacs, as well as separate umbilical cords . While non-identical twins (dizygotic or biovular twins) have placentas, amniotic sacs, and umbilical cords that are separate.

The functions of the amniotic sac

Amniotic fluid has the following main functions:

  • Protection of the fetus: * acting as a shock absorber, the fluid protects the baby from external pressures.
  • Temperature control: * insulates the baby, keeping him warm and maintaining a regular temperature.
  • Infection Control: * Amniotic fluid contains antibodies.
  • Development of the pulmonary and digestive system: * breathing and swallowing the amniotic fluid, the baby ;practices the use; of the muscles of these systems as they grow.
  • Muscle and Bone Development: * As the baby floats within the amniotic sac, they have the freedom to move around and give the muscles and bones the opportunity to develop properly.
  • Lubrication *: amniotic fluid prevents certain parts of the body such as fingers and toes from growing together; which can occur if amniotic fluid levels are low.
  • *Umbilical Cord Support: ** The fluid in the uterus prevents the umbilical cord from being compressed. This cord carries food and oxygen from the placenta to the growing fetus.

Amniotic fluid problems

There are a few conditions that can cause the amniotic sac to have more or less amniotic fluid than normal:

  • oligohydramnios , when there is too little amniotic fluid;
  • polyhydramnios , when there is too much fluid.

Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.

She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform,

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