Preterm Labor General hospital of Tianjin medical university Zhang Xuhong

In USA:morbidity 10% Neonatal morbidity and mortality 50%-70% In China:morbidity 5%-15% Neonatal mortality 15%

In USA:morbidity 10%

Neonatal morbidity and mortality 50%-70%

In China:morbidity 5%-15%

Neonatal mortality 15%

Definition Preterm labor is defined as that occuring after 20 weeks and before 37 completed weeks of gestation.

Preterm labor is defined as that occuring after 20 weeks and before 37 completed weeks of gestation.

Etiology and risk factors Etiologic subtypes of preterm labor Other undiagnosed conditions and problems High risk factors

Etiologic subtypes of preterm labor

Other undiagnosed conditions and problems

High risk factors

There are three etiologic subtypes of preterm labor Spontaneous preterm birth Preterm premature rupture of the membranes Induction of labor for medical indication: preeclamsia,cardiac disease

Spontaneous preterm birth

Preterm premature rupture of the membranes

Induction of labor for medical indication:

preeclamsia,cardiac disease

Undiagnosed conditions Placental origin Silent infection Immunologic etiology Uterine origin Cervical origin

Placental origin

Silent infection

Immunologic etiology

Uterine origin

Cervical origin

High risk factors Socioeconomic factors : race Medical and obstetric factors (1)Preterm birth occurred before (2)Second-trimester abortion and repeated spontaneous first-trimester abortions (3)Bleeding, urinary tract infection, uterine anomalies, polyhydramnios,multiple gestation… (4)Bad nutritional status,stress and anxiety

Socioeconomic factors : race

Medical and obstetric factors

(1)Preterm birth occurred before

(2)Second-trimester abortion and repeated spontaneous first-trimester abortions

(3)Bleeding, urinary tract infection, uterine anomalies, polyhydramnios,multiple gestation…

(4)Bad nutritional status,stress and anxiety

Clinical findings Uterine contractions: regular contractions at frequent intervals,generally more than 2 in onehalf hour Dilatation and effacement of cervix:2cm Vaginal bleeding: evaluate for placenta previa and placenta abruption

Uterine contractions: regular contractions at frequent intervals,generally more than 2 in onehalf hour

Dilatation and effacement of cervix:2cm

Vaginal bleeding: evaluate for placenta previa and placenta abruption

Evaluation Gestational age: 20-37;LMP and EDC Fetal weight: biparietal diameter and lenth of thighbone Presenting part: Fetal monitoring: NST( non-stress test

Gestational age: 20-37;LMP and EDC

Fetal weight: biparietal diameter and lenth of thighbone

Presenting part:

Fetal monitoring: NST( non-stress test

Infection-cervical pathway Bacteria vaginosis Vaginal-cervical infections and cervical length Fibronectin test (1)positive:22-24weeks, predictpreterm labor (2)negative:low risks

Bacteria vaginosis

Vaginal-cervical infections and cervical length

Fibronectin test

(1)positive:22-24weeks, predictpreterm labor

(2)negative:low risks

Diagnosis The diagnosis of preterm labor occurring between 20-37weeks is based on the following criteria in patients with ruptured or intact membranes (1) Documented uterine contractions （ 4 per 20 minutes or 8 per 60 minutes) (2) Documented cervical changes: cervical effacement of 80% or dilatation of 2cm or more

The diagnosis of preterm labor occurring between 20-37weeks is based on the following criteria in patients with ruptured or intact membranes

(1) Documented uterine contractions （ 4 per 20 minutes or 8 per 60 minutes)

(2) Documented cervical changes: cervical effacement of 80% or dilatation of 2cm or more

Management Adequate hydration and bed rest Vaginal examnation Culture Antibiotic therapy Laboratory tests Ultrosonic examination Tocolytic therapy

Adequate hydration and bed rest

Vaginal examnation

Culture

Antibiotic therapy

Laboratory tests

Ultrosonic examination

Tocolytic therapy

Hydration and bed rest If the patient represents preterm labor, she can not go to work or do any house work. With adequate hydration(either oral or parental) and bed rest, uterine contractions cease in approximately 20% of patients. If necessary, she should go to see doctors.

If the patient represents preterm labor, she can not go to work or do any house work. With adequate hydration(either oral or parental) and bed rest, uterine contractions cease in approximately 20% of patients.

If necessary, she should go to see doctors.

Vaginal examination No membrane rupture and no contraindications. Ascertain cervical length and dilation. Ascertain the station and nature of the presenting part of the fetus. Monitor for uterine contractions, its presence, frequency and intensity.

No membrane rupture and no contraindications.

Ascertain cervical length and dilation.

Ascertain the station and nature of the presenting part of the fetus.

Monitor for uterine contractions, its presence, frequency and intensity.

Cultures of vagina diacharge Main organisms in the etiology of preterm labor: Group B streptococcus Ureaplasma Myoplasma Gardnerella vaginalis

Main organisms in the etiology of preterm labor:

Group B streptococcus

Ureaplasma

Myoplasma

Gardnerella vaginalis

Diagnosis of bacteria vaginosis Vaginal PH > 4.5 (3.8- 4.4) Whiff test (+) : amine odor after addition of 10% potassium hydroxide Presence of clue cells Milky discharge The diagnosis can be made by the presence of three of four clinical signs.

Vaginal PH > 4.5 (3.8- 4.4)

Whiff test (+) : amine odor after addition of 10% potassium hydroxide

Presence of clue cells

Milky discharge

The diagnosis can be made by the presence of three of four clinical signs.

Antibiotic therapy Penicillin is the first chioce A 7-day course of ampicillin and/or erythromycin( no allergy) Clindamycin or vacomycin( allergy)

Penicillin is the first chioce

A 7-day course of ampicillin and/or erythromycin( no allergy)

Clindamycin or vacomycin( allergy)

Laboratory test Complete blood cell count Random blood glucose lever Serum electrolytes lever(Ca 2+ , Mg 2+ ) Urinalysis (protein, glucose, WBC,RBC) Urine culture and sensitivity

Complete blood cell count

Random blood glucose lever

Serum electrolytes lever(Ca 2+ , Mg 2+ )

Urinalysis (protein, glucose, WBC,RBC)

Urine culture and sensitivity

Utrasonic examination Detect document presentation Assess cervical length Rule out fetus congenital malformation Assess fetal weight Uterine anomaly: uterus bicornis （双角） uterus septus （纵隔）

Detect document presentation

Assess cervical length

Rule out fetus congenital malformation

Assess fetal weight

Uterine anomaly:

uterus bicornis （双角）

uterus septus （纵隔）

Uterine tocolytic therapy Uterine tocolytic agents (1) Magnesium sulfate (2) Nifedipine (3) Prostoglandin synthetase inhibitors

Uterine tocolytic agents

(1) Magnesium sulfate

(2) Nifedipine

(3) Prostoglandin synthetase inhibitors

Magnesium sulfate The first choice of tocolytic therapy Compete with calcium ions for entry into the cell at the time of depolarization Successful competition results in myometrium relaxation Appropriate serum lever is 5.5-7.0mg/dl

The first choice of tocolytic therapy

Compete with calcium ions for entry into the cell at the time of depolarization

Successful competition results in myometrium relaxation

Appropriate serum lever is 5.5-7.0mg/dl

Side effects of MgSO 4 Warmth and flushing Respiratory depression Cardiac conduction defects Decrease in fetus renal clearance Loss of muscle tone and drowsiness of neonatal

Warmth and flushing

Respiratory depression

Cardiac conduction defects

Decrease in fetus renal clearance

Loss of muscle tone and drowsiness of neonatal

Nifedipine A calcium-entry blocker Be effective in suppressing preterm labor Minimal matenal and fetal side effects Side effects include: headache, cutaneous flushing, hypotension, tachycardia

A calcium-entry blocker

Be effective in suppressing preterm labor

Minimal matenal and fetal side effects

Side effects include: headache, cutaneous flushing, hypotension, tachycardia

Prostaglandin synthetase inhibitors Indomethacin is most commonly used Side effects: oligohydramnios, fetal intracranial hemorrhage, patent ductus arteriosis Be used on a short-term basis

Indomethacin is most commonly used

Side effects: oligohydramnios, fetal intracranial hemorrhage, patent ductus arteriosis

Be used on a short-term basis

Efficacy of tocolytic therapy Prolong gestation age Improve in neonatal survival Decrease RDS Increase in birth weight of infant Benefits do not accrue to infants older than 34 weeks’ gestational age

Prolong gestation age

Improve in neonatal survival

Decrease RDS

Increase in birth weight of infant

Benefits do not accrue to infants older than 34 weeks’ gestational age

Contraindications of tocolytic therapy Severe preeclampsia Severe bleeding of placenta previa and placenta abruption Chorioamnionitis Intrauterine growth restriction Fetal anomalies and fetal death Mamagemant must be individualized.

Severe preeclampsia

Severe bleeding of placenta previa and placenta abruption

Chorioamnionitis

Intrauterine growth restriction

Fetal anomalies and fetal death

Mamagemant must be individualized.

Use of glucocorticoids for fetal pulmonary maturation Betamethasone 12mg Qd x 2 Dexamethasone 6mg Bid x 4 Optimal benefit begins 24 hours after therapy

Betamethasone

12mg Qd x 2

Dexamethasone

6mg Bid x 4

Optimal benefit begins 24 hours after therapy

Labor and delivery of the preterm infants With a vertex presentation, vaginal delivery is preferred Use of outlet forceps and an episiotomy to shorten the second stage are advocated For the breech, fetus estimated at less than 1500g,cesarean section

With a vertex presentation, vaginal delivery is preferred

Use of outlet forceps and an episiotomy to shorten the second stage are advocated

For the breech, fetus estimated at less than 1500g,cesarean section