What effect does low amniotic fluid have on the fetus?

If the amount of amniotic fluid is too low, it may be caused by fetal malformation. If it is an overdue pregnancy or the fetus has intrauterine growth retardation, it will show symptoms of too little amniotic fluid. We can also understand the health problems of the fetus through the amount of amniotic fluid.

1. Fetal malformation

For example, congenital renal agenesis, renal dysplasia, ureteral or urethral stenosis and other malformations in the fetus may lead to oliguria or anuria and cause oligohydramnios.

2. Post-term pregnancy

In post-term pregnancy, the placenta functions poorly, perfusion is insufficient, and the fetus becomes dehydrated, resulting in low amniotic fluid. Some scholars also believe that in overdue pregnancy, the fetus is overmature, its renal tubules are more sensitive to antidiuretic hormone, and the low urine volume leads to oligohydramnios. 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 growth retardation. Chronic hypoxia causes redistribution of fetal blood circulation, mainly supplying the brain and heart, while renal blood flow decreases and fetal urine production decreases, resulting in oligohydramnios.

4. Amniotic lesions

Electron microscopic observations found that the amniotic epithelial layer becomes thinner when the amniotic fluid is too low, the epithelial cells atrophy, the microvilli are short and thick, the tips are swollen, the number is small, there is squamous metaplasia, the rough inner reticular and Golgi complex in the cells are also reduced, and the desmosomes and hemidesmosomes between the epithelial cells and the basement membrane are reduced. It is believed that some unexplained oligohydramnios may be related to lesions of the amniotic membrane itself.