Premature birth

Introduction to preterm birth Preterm birth refers to childbirth between 28 weeks of gestation and 37 weeks of gestation (196 to 258 days). The literature reports that premature birth accounts for 5% to 15% of the number of deliveries. Newborns born during this period weighing 1000 to 2499g and immature organs of the body are called premature babies. The mortality rate of premature infants is 12.7% to 20.8% in China, and the smaller the gestational age in foreign countries, the lower the body weight and the higher the mortality rate. The main causes of death are perinatal asphyxia, intracranial hemorrhage and deformity. Even if the premature baby survives, there are many neurological development defects. Therefore, prevention of preterm birth is one of the main measures to reduce perinatal mortality and improve the quality of newborns. basic knowledge Prevalence ratio: 1.2% of pregnant women with a pregnancy from 28 weeks to less than 37 weeks Susceptible population: pregnant women Mode of infection: non-infectious Complications: neonatal scleredema

Cause of premature birth

Pregnant women (40%):

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

2, the cervix is incompletely closed: in the anatomy, there is no real 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 of the pregnancy. During the process of extension of the isthmus to form the lower uterus, the internal cervix is relaxed and the intra-aortic pressure is gradually increased, the cervix is passively dilated, and the amniotic sac is bulged toward the cervical canal. The membrane is ruptured due to tension changes or infection factors, and premature rupture of the membrane occurs. And to premature birth.

3, combined with 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, no Symptoms such as bacteriuria and other chronic diseases.

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

5, pregnancy complications: 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 can cause maternal systemic ischemia and hypoxia, placental perfusion is also insufficient, easy to induce 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: placenta previa, early placental stripping, 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.

Fetal placenta (20%):

1, the placenta previa and placenta early stripping.

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

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

4, premature rupture of membranes, chorioamnionitis.

Other (30%):

1. Lifestyle

Smoking, malnutrition, low weight gain during pregnancy and the use of cocaine or ethanol play an important role in preterm birth and fetal growth restriction, especially weight loss during pregnancy is important, weight gain during pregnancy can reflect the nutritional status of pregnant women to some extent, Suzhou The People's Hospital reported 25 to 30 weeks of pregnancy, and the weight gain of pregnant women in the 30 to 36 weeks was 0.27 kg/week, the premature rate was 47.22%, and the rate of premature birth was 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 is set for 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 brain damage in premature infants. Danger, the birth of low birth weight infants in the United States caused by smoking 32,000 to 61,000 per year, sexual intercourse in the third trimester can cause premature birth, due to excessive secretion of prostaglandins in the semen or vaginal bleeding caused by uterine contractions, other factors including the age of pregnant women Small (<18 years old), too large (>40 years old), underweight (<45kg=, short stature (height <150cm= and strong manual labor.

2, psychological factors

Many scholars have found that psychological stress is directly related to premature birth, such as family disharmony, aversion to children, poor economic conditions, etc. can seriously affect the mood of pregnant women, the mechanism may be mediated by corticotropin releasing hormone (CRH) The release of prostaglandins from the fetal membrane placenta is related.

3. Genetic factors

The previous history of preterm birth was significantly associated with future preterm birth. Kristensen et al.'s analysis of 13967 pregnancies in Denmark was almost identical in 1995. Women with a history of preterm birth not only had the risk of recurrence of premature birth, but the risk was also passed on to them. Children, Wang (1995) and Poller (1996) found that premature birth has family aggregation, and premature birth has racial differences. Blacks with the same socioeconomic status are 50% higher than white preterm birth rate, so premature birth is considered to be related to heredity.

4, infection during pregnancy

(1) chorioamnion infection: it is a very important cause of premature birth. The infection mainly originates from the cervix, the vaginal microbes, and some are from intrauterine infection. The pathogens include aerobic and anaerobic bacteria, Chlamydia trachomatis, Mycoplasma, etc. There are many studies on the mechanism of premature birth. It is now believed that premature infection caused by bacterial endotoxin stimulates the production of cytokines by fetal membranes. Premature cell-related factors include IL-1, TNF, IL-6, and platelet activating factor in amniotic fluid. The activation of cytokines is enhanced, and platelet activating factor is produced by the fetal lung and fetal liver. Therefore, the fetus seems to promote the premature birth caused by bacterial infection, which may help the fetus to rescue itself from the infected environment.

(2) Non-genital tract infectious diseases: such as pyelonephritis, pneumonia, malaria, flu, 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 there is a greater chance of preterm birth.

6, fetal malformations

The rate of birth defects in premature infants was 3.05%, of which 73.41% were fatal malformations.

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 and miscarriage or premature birth.

(2) excessive expansion of the uterus: 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.

Preterm birth prevention

Premature birth is preventable. The key is to diagnose early and treat in time. When one of the following three conditions occurs, you must go to the hospital for examination.

1. The lower abdomen becomes hard: in the third trimester of pregnancy, as the uterus swells, irregular uterine contractions can occur, almost without pain. It is often seen frequently at night and disappears the next morning, called physiological Sexual contractions will not cause premature birth.

If the lower abdomen is repeatedly softened, hardened and the muscles are hardened, the feeling of bloating, at least once every 10 minutes, the contraction, lasting more than 30 seconds, with the shortening of the cervical canal, that is, the threatened premature delivery, as soon as possible to the hospital for examination.

2, vaginal bleeding: a small amount of bleeding is one of the precursors of labor, but sometimes cervix inflammation, anterior placenta and placental abruption will appear vaginal bleeding, then more bleeding, should go to the hospital immediately.

3, broken water: warm water-like liquid outflow, is the early break water, but under normal circumstances is the beginning of the pain after the break, the hips can be raised, preferably flat, immediately sent to the hospital.

Preterm birth complications Complications neonatal scleredema

Because the various organ systems of premature infants are not yet mature, the living capacity is poor, and it is easy to cause diseases, such as lung diseases, intracranial hemorrhage, infection, scleredema, etc., which may leave mental retardation or sequelae of the nervous system, and about 15 in premature infants. % died in the neonatal period, and premature birth is an important cause of perinatal death.

Symptoms of premature birth, common symptoms, cervical dilatation, premature rupture, premature rupture of membranes, vaginal bloody secretions, inevitably premature delivery

symptom

As with normal delivery, there is uterine contraction, a little vaginal bleeding, often accompanied by premature rupture of membranes, cervical stenosis gradually subsided, post-expansion, etc., previous abortion, premature birth history or pregnant women with a history of vaginal bleeding during pregnancy Premature birth.

Premature birth is similar to abortion, and there are also development processes. The clinical can be divided into two stages:

1, aura of premature birth: in the mid-late pregnancy, sensitive pregnant women can feel uterine contractions, this non-fixed intermittent time, irregular duration of contractions, not really the contractions of labor, but the physiological manifestations of the uterus, or Called Braxton-Hick's contractions, such as uterine contraction intermittent time within 10min, there is a tendency to gradually shorten, contraction duration of 20 ~ 30s, and a tendency to gradually prolong, it can be considered as a manifestation of threatened premature birth, sometimes accompanied by Excretion of vaginal discharge, cervix dilatation or premature rupture of membranes.

2, inevitably premature delivery: in addition to regular uterine contractions, intermittent period is getting shorter, duration is getting longer, and the intensity is increasing, accompanied by cervix tolerance 75% and cervical dilatation 2cm; or progressive cervix The cervix is dilated and the vaginal blood secretion or membrane has been broken. The situation is similar to that of term pregnancy.

Premature birth check

1. Determination of tumor necrosis factor (TNF)

TNF is a cytokine produced by macrophages after stimulation, which can stimulate the production of prostaglandins in amniotic membrane and decidua. Therefore, it is considered that the determination of TNF in amniotic fluid is far more sensitive to the invasion of diagnostic microorganisms than Gram stain, once the amniotic fluid microorganisms Invasion stimulates the secretion of cytokine TNF into amniotic fluid, and labor 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 decidual tissue of placenta villi. It uses sensitive immunoassay (monoclonal antibody FDC-6) for cervical or vaginal secretions in late pregnancy, amniotic fluid, FF>50mg in maternal plasma. /L, which means that there is a possibility of premature delivery, which means 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 a large amount of phosphorylated IGFBP-1, while amniotic fluid, fetus Serum and maternal plasma are rich in non-phosphorylated IGFBP-1. When adjacent to the fetus, the membrane begins to separate from the decidua wall. The decidua and the chorion adhering to it are decomposed into small fragments, and a small amount of phosphorylated IGFBP. -1 leaked into the cervical secretions, the content of phosphorylated IGFBP-1 in cervical vaginal secretions 50g / L, can be predicted as a premature birth.

4. Determination of prolactin

Prolactin (PRL) is synthesized by the decidua, maternal pituitary, and fetal pituitary gland during pregnancy, and undergoes amniotic cavity through the decidua to promote prostate synthesis and fetal lung maturation. PRL is found in cervical-vaginal secretions of pregnant women, indicating Membrane-amniotic membrane separation, PRL leakage, or some factors cause sub-clinical damage or rupture of amniotic membrane to cause PRL outflow in the amniotic cavity, which can theoretically 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, but the shortcomings of the fingerprint test is objectivity, poor repeatability, and can only detect the cervix and vaginal conditions, can not understand the cervix With the development of ultrasound technology, it has opened up a new way for objective evaluation of cervical ripening. Transvaginal ultrasound and transperineal ultrasound are superior to abdominal ultrasound. Bactolucci et al. studied the ultrasound images of 48 premature pregnant women and proposed premature delivery. 4 points signs: 1 cervix length <3cm; 2 cervix internal mouth expansion> 1cm; 3 amniotic sac protruding into the neck tube; 4 uterus lower section thickness <6mm, with one can diagnose premature birth.

Premature diagnosis and identification

diagnosis

Uterine contraction and progression of labor only means that the pregnancy is coming to an end. As for whether it is a premature birth, the key is to determine the gestational age and the size of the fetus. The clinical gestational age and estimated fetal size can be estimated from the following aspects:

1. Clinical calculation:

Learn more about the previous menstrual cycle, ask about the last menstrual date, the beginning of the early pregnancy reaction and the start time of the fetal movement; according to the gynecological examination during early pregnancy, the size of the uterus is consistent with the menstrual month; refer to the current pubic uterus length and abdominal circumference to calculate the gestational age .

2, the cervical map

There are two ways to predict preterm birth based on the length of the cervix and the size of the uterine ostia at different gestational weeks:

(1) Finger examination method: including anal examination and vaginal examination, foreign vaginal examination is more, in the 25 to 31 gestational weeks, the finger examination found that the length of the cervical canal is 1cm; when the opening of the cervix can accommodate the fingertip (1cm), Premature births often occur weeks later.

(2) B-ultrasound: If B-ultrasound is found: 1 cervix retraction, internal mouth to outer neck tube length <3cm; 2 cervical tube dilatation > 1cm; 3 fetal membrane bulging into the neck tube (ie, pre-amniotic sac protruding 4; 4 lower uterus thinning <0.6cm, with the above 3 or 4, 60% of premature birth.

3. Ultrasound examination:

The fetal head diameter, head circumference, abdominal circumference, and femur length are closely related to gestational age and body weight. The gestational age and fetal size can be estimated according to the ultrasonic measurement. The measurement of the double top diameter is more accurate, and the error is less, such as 85mm, 96%. Fetal weight 2500g; reliability of femur length measurement is about 90%, such as 6.8cm, fetal weight 2500g.

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