Understanding Preterm Labor: Causes, Diagnosis, and Treatment Options

1. Preterm labor Luoxiaodong

2. Definition • Prematrue labor or delivery • Labor spontaneously occurring after 20 (viability 24~28) weeks’ but before 37 weeks’ gestation, fetal weight <2500g • before 37 and after 28 weeks’ gestational age in our country • Leading cause of neonatal morbidity in developed countries

3. Uterine contractions abdominal tightening lower back pain pelvic pressure • Cervical effacement and dilation

4. preterm labor • other similarly entities cervical incompetence preterm uterine contractions • Preterm premature rupture of membrane

5. Complicates 10-15% of all pregnancy • cause of neonatal morbidity and mortality

6. Etiology • Obstetric complications • Placenta abnormalities • Placenta previa, abruptio placenta • Diabetes, hypertension • Polyhydramnios, oligohydramnios • Premature rupture of membrane • Multiple gestation • Previous laceration of cervix or uterus • Short interval between pregnancies (<3months)

7. Etiology • Medical complications • Infection • Decidua, fetal membrane, amniotic fluid, urinary tract infection • Conization of cervix • Heavy cigarette smoking • Alcoholism or drug addiction • Maternal trauma • Severe anemia

8. Etiology • Surgical complication • Any intra-abdominal procedure • Genital tract anomalies • Incompetent cervix • Uterine anomalies • Bicornuate, unicornuate uterus, subseptate

9. Diagnosis • Clinical manifestation • Uterine contractions • Persistent lower abdominal cramping or discomfortable • Regular, twice during a 10 min, duration is 30 seconds lasting for 30min • Distinction of true and false labor • Effacement and dilation of cervix • 2cm or 80% effaced

10. Digital examination is the traditional method used to detect cervical maturation, but quantifying these changes is often difficult.

11. Diagnosis • Premature rupture of membranes(PROM) • Vaginal bleeding • Some with abruptio placenta or placenta previa • Increased vaginal discharge and pressure • Incompetent cervix

12. Diagnosis • Laboratory studies • Ultrasound: fetus, placenta • Urinalysis, culture and sensitivity testing • Complete blood count with differential

13. Discharge examination • Cervical secretion cultures Amniocentesis • L/S ratio lecithin: sphingomyelin • or foam stability test

14. Evaluation • Gestational age • Fetal weight • Presenting part • Fetal monitoring

15. Prediction • Transvaginal ultrasound • Cervical length>30mm, high negative predictive value, in the second and third trimesters • Fetal fibronectin • Protein of the choriodecidual matrix • Absent from cervicovaginal secretions after 20 weeks, until delivery begins • negative swab

16. Treatment • Goals Inhibit or reduce uterine contractions Optimize fetal status before delivery • expectant management 34 -37weeks’ >2500 g intervention 24-34 weeks’ 600-2500 g

17. Preterm labor should be allowed in following cases • Maternal diseases and disorders • Severe hypertensive disease • Pulmonary or cardiac disease • Maternal severe hemorrhage

18. Treatment • Fetal diseases and disorders • Fetal death or distress • Intrauterine infection • Polyhydramnios accompanying with malformation • Others • Cervical dilatation of more than 4cm • Ruptured membrane: controversy

19. Treatment • Bed rest • The most common interventions used for prevention and/or treatment of threatened preterm labor • Left side

20. Treatment • Inhibit uterine contraction • Hydration/sedation • Pretherapy before tocolysis • When gravida without medical complications • Pethidine: 50~100mg im

21. Treatment • Tocolysis • The fetus is healthy • Gestational week is 20~34 ( up to 37 week if no intensive neonatal care) • Cervical dilatation is <4cm and effacement is <80% • Membrane is intact • If not intact, tocolysis may be administrated for usage of corticosteroids for 24~48 hours • Until labor stops

22. Note • Shortterm goal Continue the pregnancy for 48h after steriod administration • Long-term goal Continue the pregnancy beyond 34 -37weeks

23. Treatment • Antibiotics • Culture of bacteria and drug sensitivity test • Vaginal discharge • Amnionic fluid • Urinary system

24. Treatment • Accelerating fetal lung maturity • Glucocorticoids therapy • Mature pulmonary • Beta-methasone: 12mg im, repeated once in 12~24 hours, weekly • Dexamethasone: 10mg iv, repeated once in 24 hours or 5mg im tid for 3 days

25. Optimal benefits of antenatal corticosteroids are seen 24 hours after administration, peak at 48 hours , and continue for approximately 7 days

26. Treatment • Conduct of labor • Premature breech infants 1500~2000g are delivered by CS • Avoid fetal hypoxia and intraventricular hemorrhage • Episiotomy should be made to reduce risk of injury • Aided by forceps • protect and guide the head

27. Treatment • Intensive neonatal care

28. Prognosis • chance of permanent sequelae in direct relationship to fetal size • 2000~2500g survival rate is >97% • 1500~2000g >90% • 1000~1500g 65~80% • 800~1350g 66% • Mortality and morbidity rates are higher in smaller fetuses

29. Prevention • Regular and good antenatal care • Treat pregnancy complication • Prevent premature rupture of membrane and subclinical infection • suture of cervical incompetence (cerclage) between 14th ~18th week

30. Thank you !

31. Treatment • -mimetic adrenergic agents: 2 the most common used • decrease free calcium, relax uterus and uterine vessels • Side effects: hypotension, maternal and fetal tachycardia, decreased serum K+, increased glucose and pulmonary edema • Contraindications • Cardiac disease，uncontrolled hypertension and diabetes, asthma

32. Treatment • Ritodrine: • Initial dose is 50~100 g/min increased by 50g/min, until labor stop, maintain for 12 hours. Max dose 350 g/min • 10 mg po 30 min prior to stopping iv, followed by 10 mg every 2 hr or 20mg every 4 hr for 24 hr. If stable reduce to 10~20mg every 4 to 6 hr. Max dose 120mg /day

33. Treatment • Magnesium sulfate • Best alternative of beta-mimetic drugs • Compete with calcium • Side effects: had learned before, must carefully observe • Usage

34. Treatment • Prostaglandin synthetase inhibitors • Indomethacin • 25mg po every 8 hours, after 24 hours, every 6 hours • Less used, <1 week • Not common used • Premature closure of fetal ductus arteriosus

35. Treatment • Calcium-channel blockers • Nifedipine • 5~10mg po tid • Not common used • Decrease uteroplacental blood flow and fetal hypoxia

44. Thanks!