Preterm labor is defined as delivery between 28 weeks and less than 37 weeks of gestation. Spontaneous preterm labor includes unterm delivery and premature rupture of membranes, while therapeutic preterm labor is pregnancy complications or comorbidities that require interruption of pregnancy.
Second, the diagnosis and prediction of preterm labor 1.
(1) Preterm labor: delivery before 37 weeks of gestation is called preterm labor; (2) Preterm labor: regular contractions (4 times every 20 minutes or 8 times every 60 minutes) in late pregnancy (<37 weeks), accompanied by progressive changes in the cervix (cervical tolerance ≥80%, with the opening of the uterus dilated by more than 2,0cm).
2, the prediction of preterm labor: when the pregnancy is less than 37 weeks, the pregnant woman with contractions can apply the following two methods for the prediction of preterm labor proclination.
(1), ultrasound detection of cervical length and the opening of the internal cervical opening: transvaginal measurement should be preferred for predicting preterm labor using cervical length, but transperineal or transabdominal measurement should be chosen when placenta praevia and premature rupture of membranes and reproductive tract infection are suspected. The normal values of cervical length during pregnancy are: 3,2-5,3cm for transabdominal measurement; 3,2-4,8cm for transvaginal measurement; 2,9-3,5cm for transperineal measurement. for the prediction of preterm labor in pregnant women with preterm labor or pregnant women with high risk factors for preterm labor, cervical length >3,0cm is a more reliable indicator to exclude preterm labor. The length of the cervix should be monitored dynamically in those with symptoms of preterm labor. The funnel-shaped endocervix may be temporary, and the shortening of the cervical length is clinically predictive.
(2) Determination of fetal fibronectin (fFN) in posterior vaginal vault secretions: fFN is a glycoprotein, synthesized and secreted by amnion, meconium and chorionic villus, which plays an adhesive role to fetal membranes. It can be positive in the posterior vaginal vault secretions before 20 weeks of normal pregnancy, but should be negative in the posterior vaginal vault secretions between 22 and 35 weeks of pregnancy, and positive after 36 weeks of pregnancy. The sensitivity of fFN for predicting preterm labor is about 50% and the specificity is 80% to 90% for those with symptoms of preterm labor between 24 and 35 weeks of gestation. 71% sensitivity and 89% specificity for delivery within 1 week. With symptoms of preterm labor at 24-35 weeks of gestation, but negative fFN, the negative predictive value for not delivering within 1 week is 98% and 95% for not delivering within 2 weeks. Its importance lies in its negative predictive value and the significance of the near-term prediction.
(3), Application of fFN test for combined cervical length: those with symptoms of preterm labor, premature rupture of membranes, and cervical length <3,0 cm are suspected for further testing of fFN, and if fFN is positive, there is an increased risk of preterm labor.
(4), precautions: vaginal examination and vaginal ultrasound testing cannot be performed before fFN testing, and sexual intercourse is prohibited within 24 hours.
(3) High risk factors for preterm delivery High risk factors for preterm delivery include.
1, history of preterm birth; 2, history of late miscarriage; 3, age <18 years or >40 years; 4, suffering from somatic diseases and pregnancy complications; 5, underweight (body mass index ≤18Kg/m2); 6, no prenatal care and poor economic status; 7, drug or alcohol abusers; 8, prolonged standing during pregnancy, especially standing for more than 40 hours per week; 9, history of high risk of reproductive tract infection or sexually transmitted infection, or Combined sexually transmitted diseases such as syphilis; 10, multiple pregnancy; 11, pregnancy after assisted conception techniques; 12, developmental malformations of the reproductive system.
The treatment of preterm labor and delivery includes bed rest, glucocorticoids, contraction inhibitors, broad-spectrum antibiotics and maternal-fetal monitoring.
(a) bed rest (b) glucocorticoids Glucocorticoids are used to promote fetal lung maturation and also to promote the development of other fetal tissues. The application of glucocorticoids for pregnant women before therapeutic preterm delivery and at risk of preterm delivery is suspected to reduce the risk of neonatal respiratory distress syndrome, ventricular hemorrhage and neonatal necrotizing small intestinal colitis, reduce neonatal mortality and do not increase the rate of infection.
1. Indications for the application of glucocorticosteroids.
(1) those who have not reached 34 weeks of gestation and have the possibility of preterm delivery within 7 days; (2) those who have gestational weeks > 34 weeks but have clinical evidence to confirm immature fetal lungs; (3) those who have unsatisfactory glycemic control of gestational diabetes.
2, glucocorticoid application method: dexamethasone 5mg, intramuscular injection, once every 12 hours for 2 days, or betamethasone 12mg, intramuscular injection, once a day for 2 days, or intra-amniotic injection of dexamethasone 10mg once, intra-amniotic injection of dexamethasone is suitable for patients with gestational combined diabetes mellitus. For multiple pregnancies, dexamethasone 5mg intramuscularly once every 8 hours for 2 days or 12 betamethasone mg intramuscularly once every 18 hours for 3 times.
3. Side effects of glucocorticoids.
(1) Increased blood glucose in pregnant women; (2) Reduced immunity of mother and child. Multi-course application may have certain effects on fetal neurological development, therefore, repeated prenatal and multi-course application is not recommended.
(4) Contraindications to glucocorticoids: those with confirmed evidence of intrauterine infection.
(iii) Contraction inhibitors Contraction inhibitors can prolong the gestational cycle by 2-7 days, but do not reduce the rate of preterm delivery. They help to transfer the fetus in utero to a medical center with neonatal intensive care unit facilities in a timely manner and to ensure prenatal glucocorticoid application. All contraction inhibitors have varying degrees of side effects and are not recommended for long-term use. Commonly used contraction inhibitors include: magnesium sulfate, β-adrenergic agonist, indomethacin, nifedipine and contraction antagonist, etc.
1, magnesium sulfate: calcium antagonist, inhibition of neuromuscular impulses, relaxation of smooth muscle. Pregnancy medication belongs to category B.
(1) usage: the first dose of magnesium sulfate is 5g, half an hour intravenous drip, thereafter to intravenous drip 2g/h, after contraction inhibition continue to maintain 4 to 6h after changing to 1g/h, contractions disappear after continuing to drip 12h, while monitoring breathing, heart rate, urine output, knee reflex. Monitor the blood magnesium concentration if available. Blood magnesium concentration 1, 5 ~ 2, 5 mmol / l can inhibit contractions, but the blood magnesium concentration is too high can inhibit breathing, serious cases can make the heart stop.
(2) contraindications: severe myasthenia gravis, renal insufficiency, recent history of myocardial infarction and history of heart disease.
(3) side effects: pregnant women: fever, flushing, headache, nausea, vomiting, muscle weakness, hypotension, reduced motor reflex, severe respiratory depression, pulmonary edema, cardiac arrest; fetus: no stress test NST non-responsive type increase; neonate: respiratory depression, low Apgar score, reduced intestinal motility, abdominal distension; (4) monitoring indicators: maternal urine volume, respiration, heart rate, knee reflex, Mg2 + concentration; 10% calcium gluconate 10ml should be prepared for detoxification backup when applying magnesium sulfate.
2, β adrenergic receptor agonist: ritodrine stimulates uterine adrenergic β receptors, reduces intracellular calcium ion concentration, thus inhibiting uterine smooth muscle contraction. Pregnancy medication belongs to Class B.
(1) Usage: Dissolve 100mg of ritodrine in 500ml of glucose liquid and administer intravenously at a rate of 0.05mg/min at the beginning, then increase 0.05mg every 10-15min until 0.35mg/min until contractions stop. After that, continue to maintain for 12h, gradually reduce the dose and then change to oral administration. If the heart rate is ≥ 140 times, the drug should be stopped.
(2) Absolute contraindications: heart disease, abnormal liver function, preeclampsia, prenatal hemorrhage, uncontrolled diabetes mellitus, tachycardia, hypotension, pulmonary hypertension, hyperthyroidism, chorioamnionitis in pregnant women.
(3) Relative contraindications: diabetes mellitus, migraine, episodic tachycardia.
(4) Side effects: Pregnant women: tachycardia, tremor, palpitations, myocardial ischemia, anxiety, shortness of breath, headache, nausea, vomiting, hypokalemia, hyperglycemia, pulmonary edema; fetus: tachycardia, arrhythmia, myocardial ischemia, hyperinsulinemia; neonate: tachycardia, hypoglycemia, hypocalcemia, hyperbilirubinemia, hypotension, intracranial hemorrhage.
(5) Monitoring indicators: electrocardiogram, blood sugar, blood potassium, heart rate, blood pressure, lung condition, dynamic monitoring of angina pectoris symptoms and urine volume before and after medication, and total fluid restriction to 2400 ml/24h.
3, nifedipine: calcium channel blocker, so that the intracellular calcium ion concentration decreased and inhibit contractions. Pregnancy medication belongs to category C.
(1) Usage: The first loading dose of 30mg orally or 10mg sublingually, 1 time for 20min 4 times in a row. after 90min change to 10-20mg/4-6h orally or 10mg/4-6h sublingually, apply no more than 3d.
(2) Side effects: Decreased blood pressure, palpitations, decreased placental blood flow, and slowed fetal heart rate.
(3) Contraindications: heart disease, hypotension and kidney disease.
4, indomethacin: non-steroidal anti-inflammatory drugs, prostaglandin (PG) synthetase inhibitor, has the effect of making PG levels fall, reduce the role of contractions, pregnancy medication belongs to the B / D category.
(1) Usage: 150-300mg/d, the first loading dose is 100-200mg, rectal administration, fast absorption; or 50-100mg orally, later 25-50mg/4-6h, limited to short-term application before 32 weeks of pregnancy.
(2) Side effects: pregnant women: mainly gastrointestinal symptoms, nausea, vomiting and epigastric discomfort, etc., prolonged vaginal bleeding and increased bleeding during delivery; fetus: if used after 34 weeks of gestation, decreased PG levels cause narrowing of the arterial ducts, fetal heart failure and limb edema, decreased renal blood flow, and low amniotic fluid; (3) Contraindications: peptic ulcer, indomethacin allergic patients, coagulation (3) Contraindications: peptic ulcer, indomethacin allergy, coagulation disorders and liver and kidney diseases.
5.Atosiban (contractin receptor antagonist): Atosiban is a contractin derivative, which competes with contractin for contractin receptors to inhibit contractions. Compared with other 3 different β sympathomimetic drugs, atosiban has a lower incidence of side effects and has been used clinically as a uterine contraction inhibitor in Europe, but its wider application needs to be further evaluated.
(iv) Antibiotics Although the main cause of preterm labor is due to infection, studies have shown that antibiotics do not prolong the gestational weeks and reduce the rate of preterm labor.1. For pregnant women with a history of preterm labor or other high-risk pregnancies for preterm labor, antibiotics should be applied individually in conjunction with the condition.2. For pregnant women with preterm labor with premature rupture of membranes, routine antibiotics are recommended to prevent infection (see Management of Premature Rupture of Membranes in Preterm Labor).
(e) Fetal monitoring mainly includes monitoring of fetal status, including amniotic fluid volume and umbilical artery blood flow monitoring and fetal biophysical score, timely detection of fetal distress, and evaluation of fetal growth and development and estimation of fetal weight by ultrasound measurement.
(vi) Maternal monitoring includes monitoring of vital signs, especially temperature and pulse, which can often detect early signs of infection. Blood and urine routine and C-reactive protein are reviewed regularly.
(vii) Choice of timing of delivery The choice of timing of delivery includes.
1, For unavoidable preterm labor, all contraction inhibitors should be discontinued.
2. When the risk of prolonged pregnancy is greater than the risk of fetal immaturity, prompt termination of pregnancy should be chosen.
3. The decision to terminate a pregnancy at <34 weeks of gestation is made on an individual basis. If there is a definite intrauterine infection then the pregnancy should be terminated as soon as possible. For patients with ≥34 weeks of gestation, they can follow the natural course.
(H) Choice of delivery mode The choice of delivery mode should be fully communicated with the pregnant woman and her family. 1. Caesarean section is feasible to end delivery if indicated, but it should be performed on the basis of estimating the possibility of survival of the preterm baby.
2. Vaginal delivery should be closely monitored for fetal heartbeat, and sedatives that may inhibit fetal breathing should be used with caution. Perineal laterotomy is routinely performed during the second stage of labor.
(ix) For other applications of contraction inhibitors, prevention of postpartum hemorrhage is required. Refer the preterm infant to neonatal ICN or ask an experienced physician for neonatal consultation and treatment.
V. Premature rupture of fetal membranes in preterm labor 1. Definition of preterm rupture of fetal membranes: It refers to the rupture of fetal membranes that occurs before 37 weeks of gestation without delivery, mainly caused by infection.
2. Diagnosis of premature rupture of membranes in preterm labor: through clinical manifestations, medical history and simple experiments.
(1) Medical history is very important for the diagnosis of premature rupture of membranes, so it should not be ignored and should be understood in detail.
(2) Sodium dinitrophenylazo naphthol disulfonate test paper test of vaginal secretions to detect PH ≥ 7.
(3) Take the fluid in the vaginal vault pool and place it on a glass slide, dry it and observe it under the microscope with amniotic fluid crystals. All the above tests are positive, and the accuracy of its diagnosis of premature rupture of membranes in preterm labor is 93,1%.
3, the diagnosis of intrauterine infection: determine the presence of chorioamnionitis is mainly based on clinical diagnosis. Placenta after delivery. Fetal membranes and umbilical cord pathological examination, cesarean section of the uterine cavity and newborn ear swabs for bacterial culture suspicious to help confirm the diagnosis, and can be used as a reference in the selection of antibiotics. Clinical diagnostic indicators of intrauterine infection are as follows (diagnosis can be made with 3 or more of the following)
(1) elevated body temperature ≥38°C, (2) pulse ≥110, (3) fetal heart rate >160 or <120, (4) elevated blood leukocytes up to 15?spanlang="EN-US">109/L or with nuclear left shift, (5) elevated C-reactive protein level, (6) offensive odor of amniotic fluid, (7) uterine pressure pain.
4. Treatment of premature rupture of membranes in preterm labor: vaginal bacterial culture is needed before drug treatment.
(1) antibiotics: its role is sure, it can reduce the rate of neonatal disease and death, as well as the incidence of puerperal infection. Penicillin is the preferred drug, and penicillin allergy is replaced by insured bacteriocin antibiotics.
(2) Glucocorticoid: clinically no obvious signs of intrauterine infection, can be applied, the method and dose of the same as preterm delivery.
(3) contraction inhibitors: if there are no contractions, it is not necessary to use them, if there are contractions and the pregnancy is <34 weeks, no clinical signs of infection can be applied for a short time.
(4) Termination of pregnancy: if the pregnancy is <34 weeks, if there is no intrauterine infection the umbilical cord should be used, glucocorticoids and antibiotics should be used, and the condition of mother and child should be closely monitored, if infection is found, the pregnancy should be terminated immediately. For hospitals without NICU, patients should be transferred to hospitals with NICU as soon as possible if there is no possibility of delivery in the short term. At >34 weeks of gestation, there is no need to routinely perform fetal preservation and let nature take its course.
VI. Prevention of preterm labor Prevention of preterm labor includes.
1.Improvement of personal factors and socio-economic factors.
2. Standardized prenatal care. Those with high risk factors for preterm labor should pay attention to measuring cervical length and detecting fFN in vaginal or cervical secretions during routine ultrasound examination at 20 to 24 weeks of gestation.
3.Treatment of maternal diseases, such as hypertensive disorders in pregnancy, systemic lupus erythematosus, nephropathy, systemic infections (such as pyelonephritis, pneumonia, appendicitis, etc.), syphilis, lower genital tract infections, etc.
4. Prophylactic endocervical ring ligation is only applicable to those with loose endocervical opening.
5. Pay attention to the health education and contraction monitoring of pregnant women.