What is the normal depth of amniotic fluid?

As we all know, when a mother is pregnant, her baby is in the amniotic fluid, which plays a vital protective role for the fetus. Therefore, when pregnant women are undergoing prenatal checkups, they need to check the depth of the amniotic fluid. The so-called amniotic fluid depth refers to the vertical depth of the amniotic fluid pool, which is an important indicator for prenatal checkups. So, under normal circumstances, what is the normal range of amniotic fluid depth for pregnant women?

What is the normal depth of amniotic fluid?

The normal amniotic fluid depth is 3-7cm. Before 28 weeks (7 months) of pregnancy, because there is more amniotic fluid and the fetus is smaller, the fetus has a larger range of movement in the uterine cavity and the fetal position is easy to change. After 32 weeks (8 months) of pregnancy, the fetus grows rapidly and the amniotic fluid decreases relatively.

The influence of amniotic fluid depth on pregnancy

The amniotic fluid in the pregnant woman's uterus has a buffering effect that protects the fetus from external harm. It can also maintain a suitable temperature in the uterus and allow the fetus to move freely. It is very important for pregnant women. The depth of amniotic fluid is an important indicator to determine the amount of amniotic fluid, so pregnant mothers must pay attention to checking the depth of amniotic fluid.

If the depth of amniotic fluid is ≥8cm, it means that there is too much amniotic fluid. The effects of too much amniotic fluid on pregnant women mainly include placental abruption, uterine atony, postpartum hemorrhage, etc. Due to excessive amniotic fluid, the fetus has a greater range of motion in the uterine cavity, making it easy for malposition to occur; excessive expansion of the uterus and high pressure can easily lead to premature birth. If the amniotic fluid flows out after rupture of the membranes, resulting in a decrease in uterine cavity pressure, it may cause early placental detachment. In addition, the pregnant woman's uterus is large, and excessive traction can easily lead to uterine atony and the risk of postpartum hemorrhage, which have a great impact on both the pregnant woman and the fetus.

If the depth of amniotic fluid is ≤2cm, it means that there is too little amniotic fluid. The impact of too little amniotic fluid on the fetus is mainly to increase the perinatal mortality rate and cause fetal intrauterine malformation, deformity and hypoxia. The impact on pregnant women is an increased chance of cesarean section.

The difference between amniotic fluid depth and amniotic fluid index. Amniotic fluid depth and amniotic fluid index are two different concepts. Many pregnant mothers are confused about them. Let’s take a look at the difference between amniotic fluid depth and amniotic fluid index.

Amniotic fluid depth: It is the vertical depth of the amniotic fluid pool examined by B-ultrasound. Generally speaking, an amniotic fluid depth (AFV) of 3-7cm is normal, ≤2cm indicates too little amniotic fluid, and ≥8cm indicates too much amniotic fluid. It is a medical term and an important indicator for determining the amount of amniotic fluid.

Amniotic fluid index: The uterus is divided into four quadrants: upper left, upper right, lower left and lower right. The sum of the maximum vertical depths of the dark areas of amniotic fluid in the four quadrants is the amniotic fluid index. Generally, an amniotic fluid index of 9-24cm is considered normal. If the amniotic fluid index is ≥25cm, it is diagnosed as polyhydramnios. An amniotic fluid index (AFI) of 25-35cm is mild polyhydramnios, 36-45cm is moderate polyhydramnios, and >45cm is severe polyhydramnios. When the amniotic fluid index is ≤5cm, it means oligohydramnios, and when it is ≤8cm, it means low amniotic fluid.