5331312 preterm labor and delivery
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Transcript of 5331312 preterm labor and delivery
Preterm Labor and Delivery
UNC School of MedicineObstetrics and Gynecology Clerkship
Case Based Seminar Series
Objectives for Preterm Labor
Identify the risk factors and causes for preterm labor
Describe the signs and symptoms of preterm labor
Describe the initial management of preterm labor
List indications and contraindications of medications used in preterm labor
Identify the adverse outcomes associated with preterm birth
Counsel the patient regarding risk reduction for preterm birth
“Regular” uterine contractions With
Cervical “change” or > 2 cm dilation or > 80% effacement
Definition: Preterm Labor
Preterm birth: < 37completed weeks Very Preterm birth: < 32 weeks Extremely Preterm birth: < 28 weeks
Preterm Delivery
12.5% USA (2004) 2% < 32 weeks Fetal growth
Small for gestational age < 10th % for GA
Birthweight: Low BWT < 2500 grams Very low BWT < 1500 grams Extremely low BWT < 1000 grams
Incidence
13% Rise in PTB since 1992 Multiple gestation (20% increase)
50 % twins, 90% triplets born preterm
Changes in Obstetric management Ultrasound, induction
Sociodemographic factors AMA!
No improvement with physician interventions!
Incidence
Neonatal deaths
Percentage of neonatal deaths
Disorders related to prematurity and low birth weight 4,318 23.0
Congenital malformations, chromosomal abnormalities 4,144 22.1
Maternal complications 1,394 7.4
Placenta, cord, and membrane complications 1,049 5.6
Respiratory distress 929 4.9
Bacterial sepsis 737 3.9
Intrauterine hypoxia and birth asphyxia 589 3.1
Neonatal hemorrhage 563 3.0
Atelectasis 483 2.6
Necrotizing enterocolitis 313 1.7
Neonatal deaths: death within 28 days of birth .Data adapted from: the Centers for Disease Control and Prevention, 2000.
Leading Causes of Neonatal Death (USA)
Infant mortality Over 50% of infant deaths occur among the 1.5% infants
< 1500 grams 70 % of infant deaths occur among the 7.7% of infants
< 2500 grams Morbidity
60%: 26 weeks 30%: 30 weeks
Significance
Infant Mortality
Infant Morbidity
Infant Morbidity
Non-modifiablePrior preterm birth
African-American race
Age <18 or >40 years
Poor nutrition/low pre-pregnancy weight
Low socioeconomic status
Cervical injury or anomaly
Uterine anomaly or fibroid
Premature cervical dilatation (>2 cm)or effacement (>80 percent)
Over distended uterus (multiple pregnancy, polyhydramnios)
? Vaginal bleeding
? Excessive uterine activity
Modifiable Cigarette smoking
Substance abuse
Absent prenatal care
Short interpregnancy intervals
Anemia
Bacteriuria/urinary tract infection
Genital infection
? Strenuous work
? High personal stress
Risk Factors for Preterm Birth
Stress Single women Low socioeconomic status Anxiety Depression Life events (divorce, separation, death) Abdominal surgery during pregnancyOccupational fatigue Upright posture Use of industrial machines Physical exertion Mental or environmental stressExcessive or impaired uterine distention Multiple gestation Polyhydramnios Uterine anomaly or fibroids Diethystilbesterol
Cervical factors History of second trimester abortion History of cervical surgery Premature cervical dilatation or
effacementInfection Sexually transmitted infections Pyelonephritis Systemic infection Bacteriuria Periodontal diseasePlacental pathology Placenta previa Abruption Vaginal bleeding
Risk Factors for Preterm Birth
Miscellaneous Previous preterm delivery Substance abuse Smoking Maternal age (<18 or >40) African-American race Poor nutrition and low body mass index Inadequate prenatal care Anemia (hemoglobin <10 g/dL) Excessive uterine contractility Low level of educational achievement Genotype
Fetal factors Congenital anomaly Growth restriction
Risk Factors for Preterm Birth
Prior preterm birth: Increases risk in subsequent pregnancy Risk increases with
more prior preterm births earlier GA of prior preterm birth (s)
Risk Factors for Preterm Birth
Prior PTD @ (23-27 wks) 27% Prior PPROM 13.5%
Prediction/Recurrence
First Birth Second Birth Subsequent Preterm Birth (%)
Not Preterm 4.4
Preterm 17.2
Not Preterm Not Preterm 2.6
Preterm Not Preterm 5.7
Not Preterm Preterm 11.1
Preterm Preterm 28.4
Prediction/Recurrence
80% of Preterm births are spontaneous 50% Preterm labor 30% Preterm premature rupture of the membranes
Pathogenic processes Activation of the maternal or fetal hypothalamic pituitary
axis Infection Decidual hemorrhage Pathologic uterine distention
Pathogenesis
Premature activation Major maternal physical/psychologic stress Stress of uteroplacental vasculopathy Mechanism
Increased Corticotropin-releasing hormone Fetal ACTH Estrogens (incr myometrial gap junctions)
Activation of the HPA Axis
Clinical/subclinical chorioamnionitis Up to 50% of preterm birth < 30 wks GA
Proinflammatory mediators Maternal/fetal inflammatory response Activated neutrophils/macrophages TNF alpha, interleukins (6)
Bacteria Degradation of fetal membranes Prostaglandin synthesis
Inflammation
History: Current and Historical Risk Factors Mechanical
Uterine contractions Home uterine activity monitoring
Biochemical Fetal fibronectin
Ultrasound Cervical length
Prediction of Preterm Delivery
Glycoprotein in amnion, decidua, cytotrophoblast Increased levels secondary to breakdown of the
chorionic-decidual interface Inflammation, shear, movement
Fetal Fibronectin (fFN)
Fetal fibronectin as a predictor for delivery within 7 and 14 days after sampling,
combined results
Delivery <7 days Delivery <14 days
Sensitivity Specificity Sensitivity Specificity (percent), (percent), 95 (percent), 95 (percent), 95 95 percent CI percent CI percent CI percent CI
Study group
All studies 71 (57-84) 89 (84-93) 67 (51-82) 89 (85-94)
Women with
preterm labor 77 (67-88) 87 (84-91) 74 (67-82) .
87 (83-92)
Asymptomatic 63 (26-90)* 97 (97-98) 51 (33-70) .
96 (92-100)(low risk or high-risk) women
CI: confidence interval.* Only one study included in analysis. Fixed-effects model used (homogeneity test P >0.10).
Data from: Leitich, H, Kaider, A. Fetal fibronectin - how useful is it in the prediction of preterm birth? BJOG 2003; 110 (Suppl 20):66.
Fetal fibronectin vs. Clinical assessment
of Preterm Labor Parameter Sensitivity (percent) PPV (percent) NPV (percent)
Fetal fibronectin 93 29 99
Cervical dilatation >1 cm 29 11 94
Contraction frequency 8/h 42 9 94
PPV: positive predictive value; NPV: negative predictive value.Data derived from symptomatic women and reflect the ability to predict delivery within
seven days.
Adapted from: Iams, JD, Casal, D, McGregor, JA, et al. Am J Obstet Gynecol 1995; 173:141.
Transvaginal Reproducible Simple
Sonographic Assessment of Cervical Length
(Dijkstra et al Am J Obstet Gynecol 1999)
Sonographic Assessment of Cervical Length
Sonographic Assessment of Cervical Length
Integration of ….. History Cervical length Fibronectin
Assessment of Risk
Prediction of spontaneous preterm delivery before 35 weeks gestation among asymptomatic low risk women
Adapted from: Iams, JD, Goldenberg, RL, Mercer, BM, et al. Am J Obstet Gynecol 2001; 184:652.
Cervical length < 25 mm (percent)
Fetal fibronectin (percent)
Both tests (percent)
Positive test result
8.5 3.6 0.5
Sensitivity 39 23 16
Specificity 92.5 97 99.5
Positive Predictive Value
14 20 50
Negative Predictive Value
98 98 94.4
History of Delivery 18-26 27-31 32-36 > 37
FFN (-)
CL < 25 25% 25% 25% 6%
CL 26-35 14% 14% 13% 3%
CL > 35 7% 7% 7% 1%
FFN (+)
CL < 25 64% 64% 63% 25%
CL 26-35 46% 45% 45% 14%
CL > 35 28% 28% 27% 7%
Risk of Preterm Birth (< 35 wks)
Clinical Criteria Persistent Ctx 4 q 20 min or 8 q 60 min Cervical change/80% effacement/> 2cm dil.
Among the most common admission Dx Inexact diagnosis: PTL is not PTD
30% PTL resolves spontaneously 50% of hospitalized PTL deliver @ term
Clinical Diagnosis of Preterm Labor
Two goals of management: Detection and treatment of disorders associated with PTL Therapy for PTL itself
Bedrest, hydration, sedation NO evidence to support in the literature
Management of Preterm Labor
Evaluation of Patient in Suspected PTL• Prompt eval is critical• Fetal heart monitor – to help quntify frequency and duration of
contractions• Determine status of cervix – visual inspection with speculum*
– *perform first if suspected ROM b/c digital exam may increase the risk of infection in the setting of PROM
• UA and urine culture• Rectovaginal swab for GBS• Gonorrhea and Chlamydia cultures if inidcated by history or PE• Ultrasound exam – assess GA of fetus, cervical length, estimate
amniotic fluid volume, fetal presentation and placental location• Monitor patients for bleeding – placental abruption and previa may be
associated with PTL
OPTIONS FOR MEDICAL MANAGEMENT
Drug Mechanism Efficacy Side Effects Contraindications
Beta adrenergic receptor agonist (terbutaline )
Interferes w/ myosin light chain kinase
Inhibits actin myosin interaction
? 48 hours.
No change in perinatal outcome
Tachycardia, palpitations, hypotension, SOB, pulmonary edema, hyperglycemia
Maternal cardiac disease, uncontrolled diabetes and hyperthyroidism
Magnesium Sulfate
Competes with Calcium at plasma memb (?)
Unproven Diaphoresis, flushing, pulmonary edema
Myasthesthenia gravis, renal failure
Ca Channel Blocker (nifedipine)
Directly block influx of Ca thru cell membrane
Unproven Nausea, flushing, HA, palpitations
Caution: LV dysfunction, CHF
Cyclooxygenase Inhibitors (indomethacin)
Decrease prostaglandin production
Unproven Nausea, GI reflux, spasm fetal DA, oligo
Platelet or hepatic dysfunction, GI ulcerRenal dysfunction, asthma
Recommended for: Preterm labor 24 – 34 weeks PPROM 24 – 32 weeks
Reduction in: Mortality, IVH, NEC, RDS
Mechanism of action: Enhanced maturation lungs Biochemical maturation
Antenatal Steroids
Dosage: Dexamethasone 6 mg q 12 h Betamethasone 12.5 mg q 24 h
Repeated doses - NO Effect:
Within several hours Max @ 48 hours
Antenatal Steroids
17 alpha OH Progesterone Women with prior PTB (singleton) 24 – 26 wks (16 – 20 wks) – 36 weeks
Reduces the risk of recurrent preterm birth < 37 wks 36% vs 55% < 35 wks 21% vs 31% < 32 wks 11% vs 20%
Progesterone for History of PTB
A 36 year old black female G2 P 0101 presents at 8 weeks gestation.
History: Chronic hypertension, no meds Smokes 1 ppd, Drugs (-) ETOH (+) STI – history of chlamydia, HIV positive Surgical history : LEEP, tubal ligation
Case #1
Bottom Line Concepts Preterm labor - “Regular” uterine contractions, with cervical
“change” or > 2 cm dilation or > 80% effacement, occurring before 37 weeks
There are numerous risk factors – both modifiable and non-modifiable. Counsel patients regarding ways to reduce their modifiable risk factors
Clinical assessment of risk includes consideration and evaluation of history, cervical length and fetal fibronectin
There are a variety of tocolytic drugs available, though most have unproven efficacy
Antenatal steroids are recommended for: Preterm labor 24 – 34 weeks and PPROM 24 – 32 weeks
References and Resources
APGO Medical Student Educational Objectives, 9th edition, (2009), Educational Topic 24 (p50-51).
Beckman & Ling: Obstetrics and Gynecology, 6th edition, (2010), Charles RB Beckmann, Frank W Ling, Barabara M Barzansky, William NP Herbert, Douglas W Laube, Roger P Smith. Chapter 20 (p201-205).
Hacker & Moore: Hacker and Moore's Essentials of Obstetrics and Gynecology, 5th edition (2009), Neville F Hacker, Joseph C Gambone, Calvin J Hobel. Chapter 12 (p146-150).