oligohydramnios
Introduction
Introduction to oligohydramnios In the third trimester of pregnancy, the amount of amniotic fluid is less than 300ml, called oligohydramnios. The criteria for B-ultrasound diagnosis of oligohydramnios are amniotic fluid index (AFI) <5cm or maximum sheep pool depth <2cm. Early and mid-pregnancy, the amniotic fluid is too small, mostly ending in miscarriage. When the amniotic fluid is too small, the amniotic fluid is sticky, turbid, dark green. In the past, the incidence of oligohydramnios was about 0.1%. However, in recent years, due to the widespread use of B-mode ultrasound, the detection rate of oligohydramnios is 0.5% to 4%. The incidence has increased. The lack of oligohydramnios seriously affects the prognosis of perinatal children and is valued. basic knowledge The proportion of the disease: the incidence rate of pregnant women is about 0.01%-0.03% Susceptible population: pregnant women Mode of infection: non-infectious Complications: hypertension, fetal growth restriction, fetal distress, neonatal asphyxia
Cause
Causes of oligohydramnios
Fetal malformation (15%):
Many congenital malformations, especially urinary system malformations, are associated with oligohydramnios, such as congenital kidney deficiency, renal dysplasia, polycystic kidney and urethral stricture or atresia, etc. These abnormalities lead to reduced or no formation of urine, resulting in urine. The liquid can not be discharged or discharged, no urine or oliguria, resulting in decreased amniotic fluid production, normal absorption of amniotic fluid, and finally oligohydramnios.
Placental insufficiency (5%):
The basic structure of the placenta for material exchange between the mother and the child is the maternal and child barrier of the placenta. The pathological mechanism of the placenta mother-child barrier due to edema, thrombosis, fibrosis, calcification can lead to barrier function of the placenta and mother, and the substance between the fetus and the mother. The exchange decreased, and finally led to a decrease in amniotic fluid production. The maternal volume of pregnant women with expired pregnancy remained unchanged. However, due to the above changes in the maternal-child barrier, the total effective placental material exchange area decreased, and finally the amniotic fluid was too small.
Drug effect (5%):
Many drugs can cause oligohydramnios. There are two types of non-steroidal antipyretic analgesics and angiotensin-converting enzyme inhibitors. The most studied non-steroidal antipyretic analgesics are indomethacin. Mesin can cause uterine, placental circulation decline, fetal blood volume and renal blood volume decrease, and urine production decreases.
Expired pregnancy (25%):
When the pregnancy is overdue, the placental function is reduced, the perfusion is insufficient, and the fetus is dehydrated, resulting in less amniotic fluid. Some scholars believe that when the pregnancy is overdue, the fetus is over-mature, the sensitivity of the renal tubules to diuretic hormone is increased, and the amount of urine is too small, resulting in too little amniotic fluid. The incidence of oligohydramnios caused by overdue pregnancy is 20% to 30%.
Intrauterine growth retardation (5%):
Amniotic fluid is one of the characteristics of intrauterine growth retardation. Chronic hypoxia causes fetal blood circulation redistribution, mainly supplying the brain and heart, while renal blood flow is decreased, and fetal urine production is reduced, resulting in too little amniotic fluid.
Amniotic membrane disease (5%):
Electron microscopic observation showed that the amniotic epithelial layer became thinner when the amniotic fluid was too small, the epithelial cells were atrophied, the microvilli were short and thick, the tip was swollen, the number was small, and the squamous epithelial metaplasia occurred. The coarse-grained inner mesh and the Golgi complex were also reduced in the cells. There is a decrease in desmosome and hemides between the epithelial cells and the basement membrane, and it is believed that some of the unexplained oligohydramnios may be associated with the amniotic membrane itself.
Pathogenesis
During pregnancy, the amount and composition of amniotic fluid are not fixed, but in a relatively stable and dynamic process of continuous generation and absorption, when amniotic fluid production is reduced and/or amniotic fluid absorption is increased, amniotic fluid production is less than Amniotic fluid will occur when amniotic fluid is absorbed. The mechanisms involved in amniotic fluid production and absorption are mainly fetal urine, fetal swallowing, fetal respiratory movement, fetal skin and fetal membranes (including amniotic membrane and chorion). The above mechanism varies with gestational age. Different effects, fetal urine is the main mechanism of amniotic fluid production, fetal swallowing is the main mechanism of amniotic fluid absorption, and other mechanisms may have the dual role of amniotic fluid production and absorption.
Prevention
Amniotic fluid prevention
For women of childbearing age, we should strengthen the promotion and guidance of prenatal and postnatal care, and do a good job in prenatal screening. We will establish a regular system of health checkups within 3 months of pregnancy; plan to give birth after 37 weeks of pregnancy to 40 weeks of gestation, reducing the incidence of oligohydramnios. Drugs that can affect the amount of amniotic fluid are mainly indomethacin. They can reduce the amount of amniotic fluid used to treat polyhydramnios. When using it, pay attention to the amount of amniotic fluid, reduce or stop the drug in time, and avoid causing too little amniotic fluid. The drug should not be used in pregnancy. After the week, it can cause the fetal arterial catheter to be closed early.
Complication
Amniotic fluid complication Complications, hypertension, fetal growth restriction, fetal distress, neonatal asphyxia
Complications include hypertensive disorder complicating pregnancy, fetal growth restriction, umbilical cord entanglement, amniotic fluid fecal infection rate and fetal distress, neonatal asphyxia.
Symptom
Symptoms of oligohydramnios Common symptoms Twin-venous anastomosis Postpartum labor painful severe abdominal pain Fetal intrauterine growth retardation Fetus distress pregnancy-induced hypertension suffocation
Pregnant women often feel abdominal pain during fetal movement. The abdominal circumference is higher than that of the same period of pregnancy. The uterus is highly sensitive. The slight stimulation can cause contractions. After labor, the pain is severe, the contractions are not coordinated, and the uterine cervix is slow. Prolonged labor, if the oligohydramnios occurs in early pregnancy, the membrane can adhere to the carcass, causing fetal malformation, and even limb shortage. If it occurs in pregnancy, late, the pressure around the uterus directly affects the fetus, easily causing musculoskeletal malformation Such as torticollis, curved back, hand and foot deformity, it has been confirmed that inhalation of a small amount of amniotic fluid during pregnancy contributes to the expansion and development of the fetal lung, oligohydramnios can cause lung hypoplasia, and some scholars have proposed an overdue pregnancy, intrauterine development. Delayed, pregnancy-induced hypertension, fetal heart rate changes before the official labor, should consider the possibility of oligohydramnios, oligohydramnios is prone to fetal distress and neonatal asphyxia, increase perinatal mortality, Shanghai statistics perinatal Child mortality, oligohydramnios is five times higher than normal pregnancy, so it is one of the key diseases.
Examine
Amniocentesis check
According to the condition, blood, urine, routine examination, biochemistry, liver and kidney function examination are selected.
1. B-ultrasound: It is the main method for diagnosing oligohydramnios, including qualitative diagnosis and semi-quantitative diagnosis. Under the B-ultrasound, the amount of amniotic fluid is obviously reduced, the interface between amniotic fluid and fetus is unclear, and the amniotic fluid can be made by overlapping the fetal limbs. Too few qualitative diagnoses, semi-quantitative diagnosis of oligohydramnios by further measuring the depth of the sheep pool after qualitative diagnosis. During the 28- to 40-week period of pregnancy, the B-mode ultrasound determines that the largest sheep pool diameter is stable in the range of 5.1 cm ± 2.0 cm. If the maximum vertical depth of the sheep pool (AFV) 2cm is too little oligohydramnios, 1cm is severe oligohydramnios. At present, the amniotic fluid index method (AFI) is used to diagnose oligohydramnios. This method is more accurate and reliable than AFV, AFI 8cm When the critical value of oligohydramnios is diagnosed, if the AFI 5cm, the oligohydramnios is diagnosed.
2. Direct measurement of amniotic fluid: when the membrane is broken, the amniotic fluid is less than 300ml for the diagnosis of oligohydramnios. Its nature is viscous, turbid, dark green. In addition, many round or oval nodules are often seen on the surface of the amnion. Diameter 2 ~ 4mm, light gray yellow, opaque, containing stratified squamous epithelial cells and fetal fat, the biggest shortcoming of direct measurement method is that it can not be diagnosed early.
3. Magnetic resonance technology: It is a new imaging technique that can be applied in obstetrics in recent years. In addition to accurately determining the depth of the sheep pool, magnetic resonance technology can also use three-dimensional imaging technology and volumetric calculation technology for amniotic fluid. Estimating the total amount is an important method for diagnosing too little amniotic fluid.
For patients with oligohydramnios, it is important to judge the amount of amniotic fluid by imaging technique. The larger role of imaging technique is to diagnose fetal malformation. It is the key to formulate treatment plan for fetal malformation. For intrauterine diagnosis of fetal malformation B-ultrasound Technology has been a milestone, and emerging magnetic resonance technology has greater advantages than B-ultrasound technology.
Diagnosis
Amniotic fluid diagnosis and identification
diagnosis
Mainly based on clinical manifestations, B-ultrasound and direct measurement of amniotic fluid confirmed.
Direct measurement of amniotic fluid, if the amniotic fluid <300ml is too little amniotic fluid, its nature is sticky, turbid, dark green, in addition, many round or oval nodules are often seen on the surface of the amniotic membrane, diameter 2 ~ 4mm, light Gray-yellow, opaque, containing stratified squamous epithelial cells and fetal fat, the biggest drawback of direct measurement is that it cannot be diagnosed early.
Differential diagnosis
When the oligohydramnios is too small, the uterus low height and abdominal circumference are smaller than the same pregnancy month, and should be differentiated from the following diseases.
1. Fetal growth restriction: the uterus low height is less than the 10th percentile of the normal height of the same gestational age. Before 36 weeks of gestation, the B-ultrasonic test fetal head double top diameter is less than 5 percentages of the same gestational age, and the intrauterine amniotic fluid sensation is examined. Generally speaking, there is no "real sense" of oligohydramnios. The amount of amniotic fluid in B-mode ultrasound is in the normal range. The amount of amniotic fluid is >300ml when the membrane is broken. The weight of the newborn is <2500g at the time of full-term delivery. The uterus is too tightly wrapped in the uterus. B-type ultrasound examination of the amniotic fluid dark area <2cm, or even <1cm, full-term newborn weight is often > 2500g, but fetal growth restriction often combined with oligohydramnios.
2. Premature delivery: Although the height of the uterus is small, it is consistent with the gestational age. The sensation of the amniotic fluid in the uterus is obvious. The uterus is not tightly wrapped in the carcass. The B-mode ultrasound examination of the amniotic fluid volume is within the normal range, and the fetal head double top diameter value is consistent with the gestational age. When the membrane is broken, the water volume is >300ml, and the birth weight and characteristics of the newborn are consistent with premature infants.
