What Is Oligohydramnios?

When the amount of amniotic fluid is less than 300ml, it is called too little amniotic fluid, which is a traditional concept. However, it is difficult to accurately estimate the total amount of amniotic fluid regardless of vaginal delivery or cesarean delivery. The criteria for B-mode diagnosis of oligohydramnios are amniotic fluid index (AFI) <5cm or maximum amniotic fluid depth <2cm. In recent years, the prevalence of high-risk pregnancy and the improvement and popularity of B-ultrasound technology have led to an increase in the incidence of oligohydramnios, up to 5%.

Basic Information

English name: oligohydramnios
Visiting department: Obstetrics and Gynecology

Common causes: Fetal malformations, placental insufficiency, drug effects
Contagious: no

Causes of oligohydramnios

Fetal malformation

Many congenital malformations, especially urinary system malformations, are associated with oligohydramnios, such as congenital kidney deficiency, renal dysplasia, polycystic kidney disease, and urethral stricture or atresia. The above malformations result in reduced or unproducible urine production, inability to excrete or reduce excretion of urine, anuria or oliguria, resulting in decreased amniotic fluid production, normal absorption of amniotic fluid, and oligohydramnios.

2. Placental insufficiency

The placenta is an organ for material exchange between the fetus and the mother. Decreased placental function can lead to decreased fetal blood volume, decreased fetal kidney blood supply, and ultimately reduced fetal urine production.

3. Drug effect

Many drugs can cause oligohydramnios, and non-steroidal antipyretic analgesics and angiotensin-converting enzyme inhibitors are common.

Clinical manifestations of oligohydramnios

Pregnant women often feel pain due to fetal movements. The abdominal circumference and the height of the uterine floor are less than the month of pregnancy. Fetal movement is limited and natural turning is not easy. Pregnancy is prolonged, often more than 2 to 3 weeks beyond the expected date of delivery. In the process of childbirth, primary uterine contraction weakness or uncoordinated uterine contraction often occurs, the uterine opening expands slowly, and the prolonged first stage of labor is prone to occur. Amniotic fluid is rare, sticky, and mostly yellow-green, which can cause fetal hypoxia. Various developmental abnormalities caused by lack of amniotic fluid, such as oligohydramnios occurred in early pregnancy, part of the fetal surface may adhere to the amniotic membrane, or form an amniotic membrane band, causing fingers or limbs to be disconnected; if oligohydramnios occurs in late pregnancy, fetal skin Dry like parchment. Due to the lack of amniotic fluid, the fetus is in a mandatory position in the womb, which is susceptible to compression and causes special musculoskeletal deformities, such as hand and foot deformities, back flexion, torticollis, and upper and lower limb bending. Fetal lung dysplasia is also often caused by: developmental defects in the lungs that cannot excrete fluid that maintains the amount of amniotic fluid; due to low amniotic fluid, the uterus presses the fetal chest and affects the chest wall and lungs; , Hinder lung development. In normal pregnancy, inhalation of an appropriate amount of amniotic fluid is important for the expansion and development of the fetal lung. The oligohydramnios that occur in early and mid-term pregnancy often end up with abortion of the fetus.

Oligohydramnios check

1. Choose blood, urine and stool routine examinations, as well as biochemical, liver and kidney function tests according to the condition.

2. Auxiliary inspection

(1) B-ultrasound is the main method to diagnose oligohydramnios, including qualitative diagnosis and semi-quantitative diagnosis. A B-ultrasound showed that the amount of amniotic fluid was significantly reduced, the interface between the amniotic fluid and the fetus was unclear, and the fetal limbs were clearly aggregated and overlapped, which could make a qualitative diagnosis of oligohydramnios. After qualitative diagnosis, semi-quantitative diagnosis of oligohydramnios was made by further measuring the depth of the amniotic fluid. During 28 to 40 weeks of pregnancy, the maximum amniotic fluid diameter measured by B-mode ultrasound is stable in the range of 5.1 cm ± 2.0 cm. If the maximum vertical amniotic fluid depth (AFV) 2 cm is oligohydramnios and 1 cm is severe oligohydramnios. Amniotic fluid index method (AFI) is often used to diagnose oligohydramnios, which is more accurate and reliable than AFV. AFI 8cm is the critical value for the diagnosis of oligohydramnios, if AFI 5cm is the diagnosis of oligohydramnios.

(2) Magnetic resonance technology is a new imaging technology developed in recent years that can be applied in obstetrics. In addition to accurately determining the depth of the amniotic fluid, magnetic resonance technology can also be used to estimate the total amount of amniotic fluid using three-dimensional imaging technology and volume calculation technology. It is an important method for diagnosing oligohydramnios.

Oligohydramnios diagnosis

Diagnosis is mainly based on clinical manifestations, B-ultrasound and direct measurement of amniotic fluid. Measure amniotic fluid directly, if the amount of amniotic fluid is less than 300ml when the membrane is broken, it is viscous, turbid and dark green. In addition, multiple round or oval nodules are often seen on the surface of the amniotic membrane, with a diameter of 2 to 4 mm, light grayish yellow, opaque, and containing stratified squamous epithelial cells and fetal fat.

Differential diagnosis of oligohydramnios

When oligohydramnios, the height of the uterine floor and abdominal circumference are less than the same month of pregnancy, should be distinguished from the following diseases.

Fetal growth restriction

The uterus is low and its height is less than the 10th percentile of the normal height at the same gestational week. The diameter of the double top of the fetal head of B-mode ultrasound before 36 weeks of gestation was less than 5 percentages of the same gestational week. Examination of amniotic fluid vibration in the uterus is generally more obvious, there is no "real sense" of oligohydramnios, B-mode ultrasound examination of amniotic fluid volume is in the normal range, amniotic fluid volume is> 300ml when the membrane is broken, and newborn weight is <2500g at term delivery. Those with oligohydramnios tightly wrap the uterus, and the dark area of amniotic fluid measured by B-mode examination is <2cm, even <1cm, and the weight of term newborns is often> 2500g. However, fetal growth restriction is often associated with oligohydramnios.

2. Premature birth

Although the height of the uterine floor is small, it is consistent with the gestational week. Amniotic fluid in the uterus has obvious vibration, and the uterus is not tightly wrapped around the fetus. The volume of amniotic fluid in the B-mode ultrasound examination was within the normal range, and the diameter of the fetal head double parietal diameter was consistent with the gestational week. The amount of water when the membrane was broken was> 300ml. Newborn birth weight and characteristics are consistent with premature infants.

Oligohydramnios treatment

1. Too little amniotic fluid found during pregnancy

If you have a fetal malformation, you need to terminate the pregnancy immediately.

2. Diagnosis of oligohydramnios during pregnancy

It is clear that those who have no fetal malformations and the fetus has matured can consider termination of pregnancy, and the method of termination can consider cesarean section.

3. Amniotic cavity perfusion method

Decreased amniotic fluid is the main cause of adverse effects on mothers and children during pregnancy and childbirth. Increasing the amount of amniotic fluid by amniotic cavity perfusion is a targeted treatment.

(1) Indications Increase the development of fetal viscera. Too little amniotic fluid, the fetal body is close to the uterine wall and placenta, the visceral structure is not clear, and it is difficult to determine whether the fetal malformation is combined. The amnioinfusion method can increase the sound window and improve the diagnosis rate of fetal malformations. Diagnosing atypical premature rupture of membranes For premature rupture of membranes that are difficult to diagnose, perfusion of the amniotic cavity through the abdominal wall can be diagnosed if vaginal discharge occurs. reduce the pressure of the fetus during pregnancy , fetal growth and development and movement restrictions. reduce umbilical cord compression during delivery, reduce uncoordinated uterine contraction.

(2) Types The amniotic cavity perfusion method is divided into two types according to the perfusion route: transabdominal wall and transvaginal amniotic cavity perfusion. The former is usually in the case where the membrane is not broken, and the latter is usually the membrane has been broken.

(3) Precautions Normally, the perfusion solution is normal saline, and warmed before perfusion. The perfusion rate is usually about 180ml / h, and the maximum is 800ml at a time. The perfusion power is gravity. Avoid using bolus injection and infusion pump. antibiotics, fetal lung maturation drugs and amino acid nutrients can be added to the perfusate. Pay attention to monitoring changes in uterine contraction and fetal heart rate. Can be perfused continuously or multiple times, pay attention to prevent infection.

Prognosis of oligohydramnios

Poor amniotic fluid and its effects on mothers and babies: Early-onset oligohydramnios refers to oligohydramnios that occur in the second and third trimesters of pregnancy and are relatively rare. Common causes are fetal malformations and restricted fetal growth, and pregnancy outcomes are poor. Common causes of late-onset oligohydramnios are premature pregnancy, premature rupture of membranes, fetal growth restriction, fetal distress, low blood volume in pregnant women, indomethacin pregnancy protection and captopril in women Treatment of hypertensive disorders during pregnancy. Fetal malformation usually occurs during oligohydramnios during pregnancy. This fetal malformation refers to a fetal malformation secondary to oligohydramnios, the so-called quadriplegia of oligohydramnios. The tetrad of oligohydramnios includes lung hypoplasia, special facial features, limb deformities, and stunting. Too little amniotic fluid during childbirth usually results in uncoordinated contractions, slow cervical dilatation, umbilical cord compression, and fetal distress, so the rate of cesarean section increases. Even if the vagina is delivered, delivery will be relatively difficult and prone to birth injuries. The fetus is prone to neonatal asphyxia and other neonatal diseases after birth, and the neonatal mortality rate has increased significantly.