Amniotic fluid in the third trimester mainly comes from urine excreted by the fetus and then swallowed by the gastrointestinal tract. When gastrointestinal tract is abnormal and neural tube is abnormal, polyhydramnios may occur. Most of the former can be diagnosed after birth, and the latter can be found by B-ultrasound, but some amniotic fluid is normal for fetal development. Oligohydramnios in the third trimester are mostly caused by placental dysfunction. Oligohydramnios can also occur due to abnormal development of urinary system, but it is rare and can sometimes be found by B-ultrasound. There are two ways to measure amniotic fluid volume by B-ultrasound. One is the largest sheep pond, more than 3cm and less than 8 cm; The second is to measure amniotic fluid index, and the normal range is 8~ 18cm. Amniotic fluid index less than 5cm is oligohydramnios, and pregnancy should be terminated as soon as possible.
In the third trimester of pregnancy, placental function gradually declines, and amniotic fluid will gradually decrease. But if there is oligohydramnios, we must attach great importance to it. Oligohydramnios has little influence on pregnant women and great threat to the fetus, and is often accompanied by acute fetal urinary system, such as congenital kidney deficiency and renal hypoplasia. Late pregnancy is often accompanied by overdue pregnancy and placental insufficiency. Regular prenatal examination and B-ultrasound examination found oligohydramnios. When oligohydramnios is diagnosed, we should be alert to fetal malformation, fetal hypoxia and placental insufficiency. If there is no fetal malformation, pregnant women should pay close attention to the changes of fetal movement, follow up the growth of uterus, and check the amniotic fluid level by B-ultrasound. If necessary, the placental function should be continuously measured to know whether there is fetal hypoxia. If there is fetal malformation, the pregnancy should be terminated immediately. Of course, we must be more cautious, after all, it is fate!
Effect of oligohydramnios on infants;
Oligohydramnios in early pregnancy may protect the baby's fetal membranes from attaching to the baby, affecting the development of the baby's limbs; The initial function of amniotic fluid is to cushion the pressure of the uterus on the baby. Therefore, oligohydramnios will occur in the second and third trimester of pregnancy, and uterine pressure will be excessively exerted on the baby, greatly increasing the probability of musculoskeletal malformation in the baby; There are also some cases, such as the baby's congenital urinary system development abnormality, and the decrease of urine volume leads to the decrease of amniotic fluid, and the degree of influence on the baby depends on the specific situation.