Oligohydramnios

　　So far, the generation and circulation mechanism of amniotic fluid have not been fully elucidated, and there are still many cases of oligohydramnios with unclear causes. Clinically, the following situations are common.

　　Fetal malformations such as congenital renal agenesis, renal hypoplasia, or ureteral or urethral stenosis can cause oligohydramnios due to reduced urine or anuria.

　　In the case of post-term pregnancy, the placental function decreases, the perfusion volume is insufficient, the fetus becomes dehydrated, leading to oligohydramnios. Some scholars also believe that in the case of post-term pregnancy, the fetus becomes overly mature, and the renal tubules become more sensitive to antidiuretic hormone, resulting in decreased urine output and oligohydramnios. The incidence rate of oligohydramnios caused by post-term pregnancy is up to 20% to 30%.

　　Oligohydramnios is one of the characteristics of intrauterine growth restriction (IUGR) in the fetus. Chronic hypoxia causes redistribution of fetal blood circulation, mainly supplying the brain and heart, while reducing renal blood flow, resulting in decreased fetal urine production and oligohydramnios.

　　Electron microscopy observation of amnion lesions shows that the amnion epithelial layer becomes thin when there is oligohydramnios, with atrophy of epithelial cells, short and thick microvilli, swelling at the tips, fewer in number, and the phenomenon of squamous metaplasia. The rough endoplasmic reticulum and Golgi apparatus in the cells also decrease, and the desmosomes and hemidesmosomes between the epithelial cells and the basal membrane decrease. It is believed that some oligohydramnios cases with unknown causes may be related to the inherent lesions of the amnion itself.

　　The causes of oligohydramnios are complex, and many experts in the medical community are actively studying.

　　During pregnancy, oligohydramnios usually results in fetal malformation, which refers to fetal malformation secondary to oligohydramnios, known as the oligohydramnios tetrad. Due to oligohydramnios, the uterus is tightly wrapped around the fetus, causing fetal growth and movement to be restricted, leading to abnormal organ growth and function, and finally, the typical oligohydramnios tetrad appears. The oligohydramnios tetrad includes incomplete lung development, special facial features, limb deformities, and growth retardation. During labor, oligohydramnios usually results in irregular uterine contractions, slow cervical dilation, umbilical cord compression, fetal distress, and other conditions, so the cesarean section rate increases. Even in vaginal delivery, it is relatively difficult and prone to occur, leading to birth injuries. After birth, neonatal asphyxia and other neonatal diseases are prone to occur, and the neonatal mortality rate increases significantly.

　　Pregnant women with oligohydramnios often feel abdominal pain during fetal movement during pregnancy, and the examination will find that the abdominal circumference and fundal height are smaller than those of the same pregnancy period, the uterine sensitivity is high, and mild stimulation can cause uterine contractions. Due to the small fundal height, fetal movement is restricted, natural rotation is not easy, so the occurrence of breech presentation is more common, often exceeding the expected delivery date by 2 to 3 weeks. During the delivery process, primary uterine contraction weakness or irregular uterine contraction, slow cervix dilation, and easy occurrence of the first stage of labor extension.

　　Oligohydramnios is usually thick and yellow-green, causing fetal hypoxia. During labor, the pain is severe, the uterine contractions are often not coordinated, the cervix dilates slowly, and the labor duration is prolonged. If oligohydramnios occurs in the early stage of pregnancy, the amniotic membrane may adhere to the fetus, causing fetal malformation, even limb shortness. If it occurs in the middle and late stages of pregnancy, the pressure around the uterus directly acts on the fetus, easily causing musculoskeletal deformities, such as torticollis, kyphosis, and hand and foot deformities.

　　It has been confirmed that inhaling a small amount of amniotic fluid during pregnancy helps the expansion and development of the fetal lungs, and oligohydramnios can lead to incomplete lung development. Some scholars also propose that for pregnant women with post-term pregnancy, intrauterine growth restriction, and gestational hypertension, there are changes in fetal heart rate before formal labor, and it should be considered that there is a possibility of oligohydramnios. Oligohydramnios is prone to cause fetal distress and neonatal asphyxia, increasing the perinatal mortality rate. Among the factors affecting perinatal mortality, oligohydramnios is a significant factor, so oligohydramnios is one of the diseases that should be prevented and treated as a priority.

　　To prevent oligohydramnios, it is necessary to strengthen the publicity and guidance of eugenic and eugenic education for women of childbearing age, and to do a good job in prenatal screening. Regular health checks are carried out from the 3rd month of pregnancy; plan for delivery from 37 weeks to before 40 weeks of pregnancy, to reduce the incidence of oligohydramnios. The drugs that can affect the amniotic fluid volume of pregnant women at present are mainly indomethacin, which can reduce the amount of amniotic fluid for the treatment of polyhydramnios. It is necessary to pay attention to the detection of amniotic fluid volume, and to reduce the dose or discontinue the drug in a timely manner to avoid causing oligohydramnios. This drug should not be used after 34 weeks of pregnancy, as it may cause early closure of the fetal ductus arteriosus.

　　12, Starting from the 37th week of pregnancy, perform B-ultrasound regularly. If oligohydramnios is found, it is appropriate to admit the hospital earlier. During the waiting period for delivery, oxygen therapy can be performed twice a day for 3 minutes each time, and fetal heart sounds should be listened to regularly, with attention to changes in fetal heart rate.

　　11, Teach pregnant women to self-monitor, pay attention to changes in fetal movement, and lie on their left side more often. At the same time, they can increase their water intake appropriately to increase blood circulation and, consequently, amniotic fluid volume. Repeat fetal heart monitoring every 1-3 days, and also repeat B-ultrasound examinations to timely grasp the fetal condition in utero.

　　10, During the delivery process, listen to the fetal heart regularly, and if possible, use a fetal heart monitor continuously. Report any conditions to the doctor immediately, and if oxygen inhalation is needed, inject 40ml of 5% glucose and 1g of vitamin C. If the situation does not improve, especially in cases of membrane rupture with cloudy amniotic fluid, delivery should be terminated as soon as possible. If it is estimated that delivery cannot be completed in a short period of time, an emergency cesarean section should be performed promptly.

　　9, Prepare all necessary rescue items during delivery. In case of amniotic fluid meconium contamination, clean the mouth, nose, and throat secretions promptly, and suck out the mucus and amniotic fluid containing meconium.

　　8, After delivery, dry the baby promptly, pay attention to keeping warm, and observe the newborn's overall condition. Report any abnormalities to the doctor immediately and take appropriate measures.

　　The examination for oligohydramnios usually includes B-ultrasound diagnostic method and direct measurement of amniotic fluid. Each method has its own advantages and disadvantages, and patients should choose a method more suitable for themselves for examination, and treat each examination during pregnancy with caution and care.

　　(1) B-ultrasound diagnostic method

　　To date, this method has made significant progress in the diagnosis of oligohydramnios, but there are still different opinions on the diagnostic criteria. During the 28th to 40th weeks of pregnancy, the maximum amniotic fluid pocket diameter measured by ultrasound is stable within the range of 5.1±2.1cm, therefore, the vertical depth measurement method (AFD) of the maximum amniotic fluid pocket perpendicular to the uterine contour ≤2cm is considered oligohydramnios, and ≤1cm is severe oligohydramnios. In recent years, the application of amniotic fluid index (AFI) has been advocated. This method is more sensitive and accurate than AFD. AFI ≤8.0cm is considered the critical value for diagnosing oligohydramnios, and ≤5.0cm is considered the absolute value. In addition to the amniotic fluid pocket, ultrasound also reveals unclear interface between amniotic fluid and the fetus, the placenta contacting the fetus's body obviously, and the fetus's limbs being compressed and curled.

　　(2) Direct measurement of amniotic fluid

　　The diagnosis of oligohydramnios is based on amniotic fluid less than 300ml at the time of membrane rupture, which is characterized by its sticky, turbid, and dark green nature. In addition, multiple circular or oval nodules can often be seen on the amniotic membrane surface, with a diameter of 2-4mm, pale grayish yellow, opaque, and containing stratified squamous epithelial cells and fetal fat. The direct measurement method has the major drawback of not being able to make an early diagnosis.

　　Amniotic fluid deficiency can also be alleviated by food therapy, and there are usually the following foods that can alleviate the harm caused by amniotic fluid deficiency.

　　1, Ginger and Tangerine Peel

　　Take 10g of ginger and 10g of tangerine peel, add sugar to taste, boil into syrup and take as tea.

　　2, Raw Mung Bean Powder

　　Dry 75g of raw mung beans, grind into fine powder, take 10g each time, and take with congee.

　　3, Preserved Chinese Cabbage and Lean Pork

　　Take 1g of preserved Chinese cabbage, 15g of preserved Chinese radish, 100g of lean pork shreds, appropriate amount of salt and monosodium glutamate, boil together and take as a soup, take regularly.

　　4, Fresh Lemon Juice

　　Peel and core 500g of fresh lemon, cut into small pieces, put them in a pot with 250g of sugar and soak for 24 hours, then simmer over low heat until the juice is exhausted. After cooling, mix in a little sugar and it can be eaten. Take 1 dose per day, twice a day.

　　5, Persimmon Calyx and Hearth Soil

　　Take 15g of persimmon calyx and 30g of hearth soil, boil and filter the juice, mix with sugar and take it as food.

　　6, Sugarcane Juice

　　Squeeze the juice of sugarcane and add a little ginger juice to make tea.

　　Amniotic fluid deficiency is similar to the manifestation of 'amniotic fluid atrophy and dryness' discussed in traditional Chinese medicine, which is due to weakness of Qi and blood, Yin deficiency leading to deficiency of amniotic fluid and atrophy of the fetus. The treatment of traditional Chinese medicine focuses on nourishing Qi and blood, strengthening the spleen and stomach, and nourishing Yin, so that the pregnant woman has sufficient essence and blood, and the fetus is well-nourished. The commonly used food therapy formula is 'Fetal Primordial Drink' with raw and processed rehmannia and ophiopogon. The specific method of use is: 15g of ginseng, 15g of atractylodes, 6g of prepared licorice, 10g of angelica sinensis, 15g of white peony, 15g of processed rehmannia, 20g of eucommia, 6g of tangerine peel, 15g of raw rehmannia, and 15g of ophiopogon. This formula helps to replenish Qi, nourish blood, and nourish Yin, can increase the production of amniotic fluid, and thus increase the amount of amniotic fluid. It usually takes 5-7 doses to produce a significant effect.

　　Although traditional Chinese medicine and food therapy have little side effects and can produce obvious therapeutic effects, it is only recommended for pregnant women with chronic amniotic fluid abnormalities to try, and the early treatment effect is better. For those with abnormal symptoms such as rapid increase or decrease in amniotic fluid, it is still necessary to deal with it early according to the gestational age and condition of the mother and child. For example, when the amniotic fluid is significantly reduced and the pregnancy is full term, consider terminating the pregnancy and performing induction or cesarean section.