How long does it take for amniotic fluid to appear during pregnancy?

It is well known that amniotic fluid is a substance produced in the body of every pregnant woman, and amniotic fluid is also an important factor in maintaining the baby's vital functions. It’s just that amniotic fluid does not produce in the early stages of pregnancy, but it will gradually be produced as the pregnancy months progress. So under normal circumstances, how long does it take for amniotic fluid to appear in a pregnant woman's body?

How long does it take for the placenta and amniotic fluid to form?

At 11 weeks of pregnancy, the gestational sac disappears completely and the placenta is formed. As for amniotic fluid, in the early stages, it is mainly produced by the secretion of the amniotic epithelium and the transport of the amniotic membrane. On the eighth day after fertilization, the amniotic sac will slowly begin to form, and amniotic fluid will appear at this time. As the pregnancy cycle increases, the amniotic membrane will slowly increase in size, and the amount of amniotic fluid will also slowly increase.

Amniotic fluid can reduce the impact of external vibrations on the baby and avoid the mother's discomfort when the baby moves. At the same time, the antibacterial components in the amniotic fluid reduce the baby's chance of infection. The lubricating effect of the amniotic fluid helps expectant mothers give birth smoothly. Doctors can understand the baby's health status through amniotic fluid testing. Under normal circumstances, the amniotic fluid is generally 250mL at 16 weeks of pregnancy and can reach 1000mL at 36 weeks of pregnancy. In the late pregnancy, both situations of amniotic fluid less than 300mL or more than 2000mL are extremely detrimental to the baby's development and require close monitoring.

Amniotic fluid is very important for the fetus, and the amount of amniotic fluid will have different indicator ranges in each stage of pregnancy. In the tenth week of pregnancy, the amount of amniotic fluid is only 30 ml. By the twentieth week of pregnancy, the amount of amniotic fluid will increase to 35 ml. It will reach its peak in the seventh month of pregnancy, and will slowly decrease in the last two months. Before birth, the amount of amniotic fluid will generally be around 1,000 ml. If it exceeds 1,500 ml, it is a case of polyhydramnios, indicating that the fetus has a developmental disorder of the nervous system or upper gastrointestinal tract atresia. If it is less than 500 ml, it is a case of oligohydramnios, indicating that the fetus has kidney absence or dysplasia, or urinary tract obstruction.

Is there amniotic fluid and placenta at 9 weeks of pregnancy?

At full-term pregnancy, the depth of amniotic fluid >3cm is within the normal range, 2-3cm is oligohydramnios, ≤1cm is oligohydramnios, and ≥8cm is polyhydramnios. Currently, the amniotic fluid index method is commonly used for estimation. An amniotic fluid index of >20cm indicates polyhydramnios, >8cm is in the normal range, 6-8cm indicates oligohydramnios, and <5cm indicates oligohydramnios.

In the early stages of pregnancy, amniotic fluid is mainly the dialysate that enters the amniotic cavity from the maternal serum through the fetal membrane. After the fetal blood circulation is formed, water and small molecules can pass through the fetal skin that has not yet been keratinized, which is also a source of amniotic fluid. After the second half of pregnancy, fetal urine is discharged into the amniotic cavity, which gradually reduces the osmotic pressure of the amniotic fluid and increases the levels of uric acid and creatinine. On the other hand, the fetus achieves balance by swallowing amniotic fluid. In the late pregnancy, in addition to the two important routes of amniotic fluid circulation, namely the excretion of fetal urine and the swallowing of amniotic fluid, the absorption of amniotic fluid by the fetal lungs is also a route of circulation.

The composition of amniotic fluid changes continuously as pregnancy progresses. The amniotic fluid of early and mid-pregnancy is clear, while the amniotic fluid of full-term pregnancy is an alkaline white turbid body containing small pieces of suspended matter visible to the naked eye (seed skin, epithelial cells, vellus, etc.). Its specific gravity is between 1.007-1.025, and water accounts for 98%. The remaining 1%-2% is inorganic salts and organic matter, such as calcium, magnesium ions, glucose, protein, fatty acids, bilirubin, urea, creatinine, estrogen, progesterone, placental lactogen, lysozyme and detached cells.