Preterm labor is defined as delivery between 28 weeks and less than 37 weeks of gestation. Spontaneous preterm delivery includes preterm delivery and premature rupture of membranes, and therapeutic preterm delivery is pregnancy complications or comorbidities that require termination of pregnancy.
Diagnosis and prediction of preterm labor.
1. Diagnosis of preterm labor.
(1) preterm labor: delivery before 37 weeks of gestation is called preterm labor.
(2) Preterm labor: regular contractions (4 every 20 minutes or 8 every 60 minutes) in late pregnancy (<37 weeks) with progressive changes in the cervix (cervical tolerance ≥80%, with dilatation of the uterine orifice over 2.0 cm).
2.Prediction of preterm labor: When the pregnancy is less than 37 weeks and the pregnant woman has contractions, the following two methods can be applied for the prediction of preterm labor prodromal delivery.
(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 in case of suspected placenta praevia and premature rupture of membranes and reproductive tract infection, transperineal measurement or transabdominal measurement should be chosen. The normal values of cervical length during pregnancy are: 3.2-5.3 cm for transabdominal measurement, 3.2-4.8 cm for transvaginal measurement, and 2.9-3.5 cm for perineal measurement, and for the prediction of preterm labor in pregnant women with preterm labor or those with high-risk factors for preterm labor: cervical length >3.0 cm is a more reliable indicator to rule out preterm labor. The length of the cervix should be monitored dynamically for those with symptoms of preterm labor. The funnel-shaped endocervical opening 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, which is synthesized and secreted by amnion, meconium and chorionic villus and 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 can be positive after 36 weeks of pregnancy. The sensitivity of fFN for predicting preterm labor is about 50% and the specificity is 80%-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 combined fFN test for 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, the risk of preterm labor is increased.
(4) Precautions: vaginal examination and vaginal ultrasound testing cannot be performed before fFN testing, and sexual intercourse is prohibited within 24 hours.
Risk factors for preterm labor
The high-risk factors for preterm labor 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 ≤ 18 Kg/m2).
6, no prenatal care and poor economic status.
7, drug or alcohol abusers.
8, prolonged standing during pregnancy, especially for more than 40 hours per week
9, a history of high risk of reproductive tract infections or sexually transmitted infections, or combined sexually transmitted diseases such as syphilis.
10, multiple pregnancies.
11, pregnancy after assisted conception techniques.
12, developmental malformations of the reproductive system.
IV. Treatment of preterm labor and delivery
The treatment of preterm labor includes bed rest, glucocorticoids, contraction inhibitors, application of broad-spectrum antibiotics and maternal-fetal monitoring, etc.
(a) Bed rest
(B) Glucocorticoids
The role of glucocorticoids is to promote fetal lung maturation, and also to promote other fetal tissue development. 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) gestational weeks >34 weeks but with clinical evidence of immature fetal lungs
(3) Gestational diabetes mellitus with unsatisfactory glycemic control.
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 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 sugar in pregnant women.
(2) Reduced immunity of mother and child. The multi-course application may have certain effects on fetal neurological development, therefore, repeated prenatal and multi-course applications are not recommended.
4. Contraindications to glucocorticosteroids: Those with confirmed evidence of intrauterine infection.