Premature birth is inevitable

Introduction Inevitably premature delivery: in addition to regular uterine contractions, intermittent period is gradually shorter, duration is longer, and the intensity is increasing, accompanied by cervix tolerance 75% and cervical dilatation 2cm; or progressive cervical tolerance And cervical dilatation, and vaginal blood secretions or fetal membranes have been broken, the situation is similar to the full-term pregnancy clinical.

Cause

(1) There are no obvious reasons for the premature birth of about 30% of the cause of the disease. Common incentives are:

1, pregnant women

(1) excessive expansion of the uterus: twin or multiple pregnancies, too much amniotic fluid can make the intrauterine pressure high, early delivery and premature birth.

(2) Cervical stenosis: In anatomy, there is no true sphincter-like arrangement in the uterine neck. The connective tissue is mainly composed of collagen fibers, which is elastic and has a sphincter-like effect on the cervix. In the second trimester, the uterine isthmus extends to form the lower uterus. The internal cervix is relaxed and the amniotic cavity pressure is gradually increased. The cervix is passively dilated. The amniotic sac bulges toward the neck tube. The membrane is broken due to tension changes or infection factors. Premature rupture of premature rupture of membranes.

(3) acute or chronic diseases, such as viral hepatitis, acute nephritis or pyelonephritis, acute appendicitis, viral pneumonia, high fever, rubella and other acute diseases; heart disease, diabetes, severe anemia, hyperthyroidism, hypertension, Chronic diseases such as asymptomatic bacteriuria.

(4) combined with uterine malformations (such as double-horned uterus, mediastinal uterus), cervical relaxation, uterine fibroids.

(5) Pregnancy comorbidity: pregnancy with chronic nephritis, pregnancy with heart disease, pregnancy with hepatitis and pregnancy with lupus erythematosus, etc. On the one hand, due to medical complications, the mother can cause systemic ischemia and hypoxia, and the placental perfusion is also insufficient. Inducing premature birth; on the other hand, the severity of the disease poses a danger to the mother and causes iatrogenic preterm birth for the safety of the mother.

(6) Pregnancy complications of placenta previa, early exfoliation of the placenta, pregnancy-induced hypertension syndrome, intrahepatic cholestasis of pregnancy.

(7) Smoking, drug abuse, alcoholism, severe malnutrition.

(8) Others, such as long-distance travel, climate change, residential plateau, family migration, emotional volatility and other mental and physical burdens; direct abdominal impact, trauma, sexual intercourse or surgical stimulation.

2, fetal placenta

(1) Early placenta and placenta were stripped early.

(2) too much or too little amniotic fluid, multiple pregnancy.

(3) fetal malformation, fetal death, abnormal fetal position.

(4) premature rupture of membranes, chorioamnionitis.

The common causes of preterm birth are shown in Figure 1.

(two) pathogenesis

1. Lifestyle: such as smoking, malnutrition, less weight gain during pregnancy, and the use of cocaine or ethanol plays an important role in preterm birth and fetal growth restriction. In particular, less weight gain during pregnancy is important. The weight gain during pregnancy can reflect the nutritional status of pregnant women to a certain extent. Suzhou People's Hospital reported that the weight gain of pregnant women in the 25 to 30 weeks and 30 to 36 weeks of pregnancy increased by 0.27 kg/week, and the preterm birth rate was 47.22%, while >0.27 kg. / Week, the preterm rate decreased to 18.75% (P <0.01). Some foreign scholars have investigated the effect of the number of meals during pregnancy on preterm birth. The best diet mode is set to three meals a day plus 2 or more snacks. The number of meals is related to premature birth. Alcohol abuse not only causes premature birth, but also significantly increases the risk of brain damage in premature infants. Every year, 320,000 to 61,000 low birth weight children are born in the United States due to smoking. Sexual intercourse in the third trimester can lead to premature birth, due to more secretion of prostaglandins in the semen or vaginal bleeding caused by uterine contractions. Other factors include under-aged pregnant women (<18 years old), oversized (>40 years old), underweight (<45kg=, short stature (height <150cm= and strong manual workers).

2. Psychological factors: Many scholars have found that psychological tension is directly related to premature birth. Such as family disharmony, disgusting children, poor economic conditions, etc. can seriously affect the mood of pregnant women. The mechanism may be related to the release of prostaglandins from the placental tissue of the placenta by corticotropin releasing hormone (CRH).

3. Genetic factors: The previous history of preterm birth was significantly associated with future preterm birth. In 1995, Kristensen et al. analyzed the results of 13967 pregnancies of Danish women almost identically. Women with a history of preterm birth not only have the risk of recurrence of premature birth, but the risk is also passed on to their children. Wang (1995) and Poller (1996) found that premature birth has a family aggregation phenomenon. In addition, premature births have racial differences, and blacks with the same socioeconomic status are 50% higher than whites. Therefore, premature birth is considered to be related to heredity.

4. Infection during pregnancy

(1) chorioamnion infection: a very important cause of premature birth. The infection mainly originates from the microbes of the cervix and vagina, and partly from intrauterine infection. Pathogens include aerobic and anaerobic bacteria, Chlamydia trachomatis, Mycoplasma and the like. There are many studies on the mechanism of infection causing preterm birth. It is now believed that infection causes preterm birth due to cytokines produced by bacterial endotoxin-stimulated fetal membranes. Cellular active factors related to preterm birth include IL-1, TNF, IL-6. Platelet activating factor in amniotic fluid enhances cytokine activation. Platelet activating factor is produced by fetal lung and fetal liver. Therefore, the fetus seems to promote the premature birth caused by bacterial infection, which may help the fetus to save itself from the infected environment.

(2) Non-genital tract infectious diseases: such as pyelonephritis, pneumonia, malaria, influenza, etc., can activate the prostaglandin activity to cause contractions.

5. Premature rupture of membranes: 57% of premature births occur after premature rupture of membranes, especially those with premature rupture of membranes, and the chance of preterm birth is greater.

6. Fetal malformation: The birth defect rate of premature infants is 3.05%, of which fatal malformation accounts for 73.41%.

7. Uterine abnormalities

(1) uterine malformations: such as single-horned uterus, double uterus, uterine mediastinum, etc., due to dysplasia, uterine cavity is too small or irregular shape, abortion or premature birth.

(2) excessive uterine expansion: such as twin or multiple births, excessive amniotic fluid can increase the pressure of the uterine cavity, resulting in early labor and premature birth.

(3) Cervical internal stenosis is incomplete: in patients with congenital cervical dysplasia and various causes of cervical injury or tear, cervical sphincter-like function is weak, after the second trimester, in the process of extension of the isthmus to form the lower uterus, the cervix The internal mouth is loose or the continuity of the cervical connective tissue is destroyed, while the intra-amniotic cavity pressure is gradually increased, the cervix is passively dilated, and the amniotic sac is bulged from the cervical canal and exposed to the external cervix, eventually resulting in infection and increased intrauterine pressure. The membrane is ruptured and premature.

an examination

Related inspection

Vaginal secretion examination

1. Determination of tumor necrosis factor (TNF): TNF is a cytokine produced by stimulation of macrophages, which can stimulate the production of prostaglandins in amniotic membrane and decidua, so it is considered that the determination of TNF in amniotic fluid is far more than the diagnosis of microorganisms by Gram staining. The invasion is more sensitive. Once the microbial invasion of the amniotic fluid stimulates the secretion of cytokine TNF into the amniotic fluid, childbirth is inevitable. Therefore, preterm birth can be predicted by measuring the presence or absence of TNF in amniotic fluid.

2. Determination of fetal fibronectin: Fetal fibrinectin (FFN) is a protein synthesized from the tissue of placental villus. Sensitive immunoassay (monoclonal antibody FDC-6) cervix or vaginal secretions in the late pregnancy, amniotic fluid, maternal plasma FF> 50mg / L, which means that there is a possibility of preterm birth. It indicates that under the action of contraction or due to rupture of the membrane, the chorion is separated from the decidua, releasing intact or degenerate villus components and entering the cervix and vaginal secretions.

3. Determination of insulin-like growth factor binding protein-1: Insulin-like growth factor binding protein-1 (IGFBP-1) is a secreted protein cultured by decidualization of human endometrial basal cells. It has been found that decidual cells and human liver secrete large amounts of phosphorylated IGFBP-1, while amniotic fluid, fetal serum and maternal plasma are rich in non-phosphorylated IGFBP-1. When the fetal membrane begins to separate from the aponeurosis wall, the decidua and the chorion adhering to it are decomposed into small fragments, and a small amount of phosphorylated IGFBP-1 leaks into the cervical secretions. Phosphoric acid in the cervix secretion The content of IGFBP-1 is 50g/L, which can be used as a predictor of preterm birth.

4. Determination of prolactin: Prolactin (PRL) is synthesized by the decidua, maternal pituitary gland, and fetal pituitary gland during pregnancy, and is performed in the amniotic cavity through the aponeurosis to promote prostate synthesis and fetal lung maturation. PRL was found in the cervix-vaginal secretions of pregnant women, indicating decidual-amniotic membrane separation, PRL leakage, or a factor that caused sub-clinical damage or rupture of the amniotic membrane to cause PRL outflow in the amniotic cavity. In theory, it can be used as a means of predicting preterm birth.

B-ultrasound diagnostic criteria, for a long time, the understanding of the degree of cervical dilatation and withdrawal, relying on the traditional Bishop score. However, the shortcoming of the fingerprint test is that the objectivity and repeatability are poor, and only the cervix and vaginal area can be detected, and the full length of the cervix cannot be understood. With the development of ultrasound technology, a new way has been opened for the objective evaluation of cervical ripening. Transvaginal ultrasound and transperineal ultrasound are superior to abdominal ultrasound. Bactolucci et al studied the ultrasound image changes of 48 premature pregnant women, and proposed 4 signs of premature birth: 1 cervical length <3cm; 2 cervical internal opening >1cm; 3 amniotic sac protruding into the neck; 4 lower uterine thickness <6mm. Have one to diagnose premature birth.

Differential diagnosis

False contractions: pregnant women standing or sitting in the same position for a long time, will feel the hardening of the abdomen (that is, the symptoms of tight stomach), which is characterized by irregular time, the degree is also strong and weak . Before the birth, due to the pulling stimulation caused by the lower fetal head, the "false contraction" will become more and more frequent.

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