Amniotic fluid is not ordinary water, it is vital to the normal growth and development of the fetus, and in folklore there are some about the source of amniotic fluid, to say it may make you shocked, in fact, in the mid-pregnancy, the main source of amniotic fluid is the fetus’s urine, and another secondary source of fluid secreted by the fetal lungs. In late pregnancy, the fetus can produce more than 1,000mL of urine per day, so much amniotic fluid must have a way out, otherwise it will lead to excessive amniotic fluid. The main way of amniotic fluid absorption is swallowed by the fetus, to put it bluntly, “how to pee out, how to drink down”, can not urinate and defecate anywhere is reasonable, right? If the fetus “poop” in the uterus, it must be mixed with urine and swallowed. But don’t get too hung up on it. Fetal urine and feces are relatively clean, and amniotic fluid also has antibacterial properties. Another secondary route of amniotic fluid absorption is the blood vessels on the surface of the placenta. Functions of amniotic fluid Amniotic fluid can provide a space for the fetus to move, which is important for the development of the musculoskeletal system of the fetus; the fetus can swallow amniotic fluid for the development of its gastrointestinal tract is also very important, amniotic fluid can also provide the fetus with a constant temperature of the protective environment, so that the fetus is not subjected to the uterus of the direct pressure, as well as in the pregnant woman’s abdominal shock to make the fetus free from injury. Amniotic fluid also has another special anti-bacterial function that decreases the chances of intrauterine infection in the fetus. Excessive Amniotic Fluid The amount of amniotic fluid cannot be measured directly clinically, and the commonly used aid in determining the amount of amniotic fluid is ultrasound. If a single maximum pool of amniotic fluid is used as the standard, more than 8 cm is considered to be excess amniotic fluid, and if the Amniotic Fluid Index (AFI, which is the addition of amniotic fluid from the four quadrants) is used, more than 25 is considered to be excess amniotic fluid. The most common causes of amniotic fluid overload are fetal malformations, twin births, and diabetes mellitus. The most common fetal malformations associated with amniotic fluid overload include central neurologic malformations (e.g., anencephaly) and gastrointestinal anomalies (e.g., esophageal atresia, duodenal atresia). In the case of amniotic fluid overload, the most important thing is to look for the cause, including further detailed scanning of the fetal structures by an ultrasound specialist, MRI if necessary, and fetal chromosomal testing. Even after a thorough and detailed examination, the cause of amniotic fluid overflow is not identified in about 70% of cases. Serious complications of amniotic fluid overload include premature rupture of membranes, preterm labor, placental abruption, and postpartum hemorrhage due to weak contractions. In most cases, amniotic fluid does not require intervention if there is no other maternal or fetal evidence. If there is a significant increase in the amount of amniotic fluid over a short period of time, resulting in severe discomfort and respiratory distress for the mother, amniocentesis may be considered to release the amniotic fluid. For most mothers-to-be with amniotic fluid, there is no need to be overly concerned, as the prognosis for babies with unexplained amniotic fluid, mild amniotic fluid, and amniotic fluid with no detectable fetal abnormalities is better in most cases. Hyponatremia A baby with ≤2 cm of amniotic fluid is considered to have hyponatremia if the single largest pool of amniotic fluid is used as a criterion, and a baby with ≤5 cm of amniotic fluid is considered to have hyponatremia if the Amniotic Fluid Index (AFI) is used. The prevalence of oligohydramnios ranges from 1-2%, and the most common causes are fetal malformations (mainly abnormal renal development) and reduced fetal urine output due to placental dysplasia (which is often accompanied by fetal growth retardation). The incidence of adverse perinatal fetal prognosis associated with hypoamniotic fluid is higher compared to that of amniotic fluid, including fetal malformations, preterm labor, stillbirth, and fetal lung dysplasia. In terms of management, the main focus is to find the cause of the disease, strengthen monitoring, and terminate the pregnancy promptly if necessary. Some foreign medical institutions will do amniotic fluid infusion to prolong the gestational week and reduce complications, which is done less in China.