The first trimester refers to the period from the first trimester to the 12th week of pregnancy, when the fetal organs and tissues are forming and developing, and there is less amniotic fluid production and accumulation. In the first trimester, the amniotic fluid surrounding the fetus mainly comes from the placenta and maternal blood. As the gestational age increases, the fetus begins to produce urine, gradually increasing the amount of amniotic fluid. Generally speaking, the second trimester (from 13 weeks to 27 weeks of pregnancy) is the period when the amount of amniotic fluid increases the fastest.
Does the embryo contain amniotic fluid in the first trimester?
In the first trimester, the embryo does not contain amniotic fluid. Amniotic fluid is filled with fluid produced by the fetus\’ urine and placenta after the embryo has developed to a certain extent. In the early stages of embryonic development, the embryo is called a blastocyst. There is a vesicle around the embryo, called the blastocyst sac. The blastocyst sac is filled with fluid, but it is not amniotic fluid. Amniotic fluid is produced after the placenta is formed in the blastocyst sac. The placenta supplies nutrients and oxygen to the fetus through the mother\’s blood. The urine excreted by the fetus is collected in the blastocyst sac to form amniotic fluid. Therefore, the production of amniotic fluid and embryonic development to a certain stage are closely related.