Normal range of amniotic fluid index at 31 weeks of pregnancy

Pregnant women should understand the amniotic fluid, especially early pregnant women. They should pay more attention to the relevant knowledge about the development of the baby and should not ignore their own health. After checking the amniotic fluid index, we can refer to the amniotic fluid index standard to determine whether the amniotic fluid of the pregnant woman is normal. So now let's take a look at: What is the amniotic fluid index standard? What is the normal amniotic fluid index at 31 weeks of pregnancy?

What is the amniotic fluid index at 31 weeks of pregnancy?

Amniotic fluid index: The uterus is divided into four quadrants: upper left, upper right, lower left and lower right. The sum of the vertical depths of the larger dark areas of amniotic fluid in the four quadrants is AFL. If the AFL exceeds 24cm, it is diagnosed as polyhydramnios. If the AFL is between 18-24cm, it is abnormal polyhydramnios or too much amniotic fluid.

Accurate measurement of amniotic fluid in pregnant women: Accurate measurement of amniotic fluid in pregnant women is an important indicator to assess whether the pregnancy is normal. At present, most hospitals use ultrasound to control the amniotic fluid flow, and use the "amniotic fluid index method" to determine whether the amniotic fluid flow is normal. The method is to divide the uterus into four quadrants, accurately measure the maximum depth of the amniotic fluid in each quadrant, and then add them together to calculate the amount. The total value is normal in the range of 8 to 27 cm, oligohydramnios is less than 8, and polyhydramnios is more than 24.

The fetus grows slowly at 31 weeks, and its bones and organs develop more completely and strongly. At this time, the fetus can already hear the sounds outside the mother's body. Height 42 - 46 cm, weight 2KG - 2.7KG..Special reminder: biparietal diameter: 7.79 - 8.18 cm, humerus: 5.54 cm, femoral head: 6.55 cm, chest size: 22.3 cm, fetal abdominal circumference: 25.36 cm, amniotic fluid index: 15 - 16 cm.

Causes of low amniotic fluid

1. Malformed fetus

For example, if the fetus has congenital renal defects, renal dysplasia, urethral tube or urethral stenosis and other malformations, resulting in oliguria or anuria, it will cause oligohydramnios.

2. Post-term pregnancy

In case of overdue pregnancy, the placenta function is reduced, the amount of fluid injection is insufficient, the fetus is dehydrated, and there is less amniotic fluid. Some scientists also believe that during prolonged pregnancy, the fetus is too mature, its renal tubules are less sensitive to adrenal hormones, and the amount of urine is less, resulting in too little amniotic fluid. The incidence of oligohydramnios caused by post-term pregnancy is as high as 20% to 30%.

3. Intrauterine growth retardation (IUGR)

Oligohydramnios is one of the characteristics of intrauterine language development retardation in the fetus. Chronic hypoxia causes redistribution of the fetal blood circulation, mainly supplying the brain and heart, while renal blood volume decreases and fetal urine conversion decreases, resulting in oligohydramnios.

4. Amniotic membrane disease

Transmission electron microscopy revealed that the epidermis of the amniotic membrane became soft when there was too little amniotic fluid, the squamous epithelial cells shrank, the microvilli were short and thick, the tips were swollen, and the number was small. There was squamous metaplasia, the rough inner reticular tissue and Golgi complex in the somatic cells also decreased, and the desmosomes and hemidesmosomes between the squamous epithelial cells and the basement membrane decreased. It is believed that some unclear causes of oligohydramnios may be related to amniotic membrane disease itself.