This document discusses preterm labor and delivery. It notes that the most common causes of preterm delivery are spontaneous preterm labor (50%), spontaneous premature rupture of membranes (30%), and medically necessary early delivery (20%). While the specific cause is unknown in 50% of cases, risk factors include previous preterm deliveries, infections, smoking, and socioeconomic status. Complications in the current pregnancy like bleeding, preeclampsia, or infections can also contribute to preterm labor. The document outlines goals and treatments for preterm labor, including prolonging the pregnancy to allow for corticosteroid administration and safe transfer if needed. Tocolytic agents are discussed as ways to delay labor temporarily. Potential neonatal complications of

1. Maru M/MD/
For Anesthesia 2nd
09/09/2010Ec

3.  Spontaneous preterm labor -50%
 Spontaneous PROM -30%
 Medically necessary delivery- 20%
)

4.  Cause is unknown in 50% of cases
 Cause is of multifactorial and associated with
different factors
1. High risk factors:
 Previous history of preterm labor, induced or
spontaneous abortion
 Asymptomatic Bactriuria/UTI
 Smoking
 Low socioeconomic status/ Nutritional status/vt
c def/

5. 2. Complications in current pregnancy:
Maternal, fetal or placental
 Maternal:
- Pregnancy complications: APH, PROM,
Preeclampsia, polyhydraminos
- Uterine anomalies: Cervical incompetence,
malformations of the uterus
- Medical & surgical illness: acute fever, appendicitis,
etc.
- Genital tract infections: BV, T vaginalis chlamydial,
etc.

6.  Fetal: Multiple pregnancy, Congenital
malformations, IUFD
 Placental: Infarction, thrombosis, Abruption
3. Iatrogenic: wrong GA estimation
4. Idiopathic: Half of cases

7.  Labor initiation mechanism is not known as is
in normal labor. But probable mechanisms
include:
1. Activation of fetal hypothalamic-pituitary-
adrenal axis
2. Bacterial colonization(infection)
3. Decidual hemorrhage
4. Pathologic uterine enlargement

8. Activation of HPA axis
-Premature activation can initiate PTB
-Physical or psychological stress of the mother
-Uteroplacental vasculopathy –major
-evidence of placental ischemia
-severe preeclampsia is associated
with three fold increase
# 25-50% of PTD display evidence of
uteroplacental vasculopathy.

9. Mechanisms:
-increase release of CRH-
“Placental Clock”
-increased release of foetal pituitary
ACTH (fig)

11. Infection
- link between spontaneous PTB & both systemic
& ascending genital infection
-may account for 50% PTB before 30 weeks
-inflammatory response is the final common
pathway

13. Decidual haemorrhage
-thrombin binds to decidual membrane
receptors that regulate the expression of
proteases & metalloproteinases
-degradation of foetal membrane
extracellular matrix , which can result PPROM

14. Pathological uterine distension
-formation of gap junctions,
-up regulation of oxytocin receptors
-production of PGE2 &F2 & MLCK

15.  symptoms/ signs
 general physical examination
 sterile speculum examination
-pH , fern, pooled fluid
cervical examination
- cervix >=3cm/80% effaced –PTL
confirmed, evaluate for tocolysis
-cervix 2-3cm & <80% effaced –PTL likely but
not established
-cervix<2cm & 80% effaced- PTL diagnosis is
uncertain

transabdominal ultrasound

16.  use of cervical ultrasound
-cervical length <20mm & contraction
criteria met(4 in 20min,8 in 60min) PTL
-cervical length 20-30mm & contraction
criteria met – probable PTL
-cervical length >30mm – PTL very
unlikely regardless of contraction
frequency

17. Goals & Efficacy of Treatment
Ultimate goal- delivery of an infant who suffers
none of the sequelea of prematurity!
The goals of treating acute episode of idiopathic
PTL are:
 Administration of corticosteroids
 Safe transport of the mother
 Prolong pregnancy
 Antibiotic prophylaxis
Initial evaluation of the patient:
-risks & benefits of continuing the
pregnancy
-potential causes of PTL should be
sought

18. Prerequisites for treatment :
 presence of PTL
 gestational age < 34 weeks
-lowest gestational age –controversial
15 weeks , 20 weeks,24wks
-upper gestational age- 34weeks
Contraindications to labor inhibition:
 IUFD
 Lethal foetal anomaly
 NRFHR pattern
 Severe IUGR
 Chorioamnionitis
 Maternal haemorrhage with hemodynamic instability
 Severe preeclampsia

19.  Bed rest
 Adequate hydration
 Prophylactic antibiotics**
 Tocolytic agents: delay labor for adminstration of
corticosteroids and in utero referral

20. 1. Prostaglandin synthase inhibitors. Eg. Indomethacin,
Sulindac
2. Calcium Channel Blockers. Eg. Nifedipine
3. β- Adrenergic agonists. e.g. Ritodrine , terbutaline ,
salbutamole
4. Magnesium Sulfate

21. Mechanism of action: prevention of PGs production
by inhibiting cyclo-oxygenase enzymes
 PGs are important for
- Increase gap junction
- facilitate cervical ripening
- increase free intracellular ca+2
, etc

22. Mechanism of action:
 Decrease intracellular calcium
 Inhibits release of ca+2 from intracellular
storage sites
↓↓ Ca+2
↓↓M L C K ↓↓M – C interaction
 ↑↑myometrial muscle relaxation

23. Mechanism of action:
 inhibiting myosin light chain phosphorylation
 reducing intracellular ca+2
ion concentration
- ↓↓ ca+2 release from storage sites
- ↑↑ ca+2 efflux
- ↓↓ ca+2 influx

24. Mechanism of action:
 It is a calcium antagonist*
 Inhibits uterine contractility by competition with
ca+2 for entry in the calcium channel of the
myocytes
 Has neuroprotection effect for the fetus
 Not FDA approved

25. -Foetal monitoring
-tolerate labor poorly
-course of labor is significantly shorter
-delivery –principal goals of intrapartum
management are :
-avoidance of perinatal acidosis
-avoidance of birth trauma
-generous episiotomy
-prophylactic forceps- no benefit !
-C/S delivery: not routine!

26.  RDS
 Birth injury
 IVH
 Metabolic complications: Hypocalcemia,
hypoglycemia, hypomagnesmia
 Hypothermia
 NEC
 Hyperbilirubinemia
 Infection
 Malnutrition

27.  High perinatal mortality & morbidity
 With good NICU: survival for 1000-1500gm is
90%
 With help of surfactant, neonates born at 28
weeks have survival of 75%

28. Thank You
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