It is the presence of contractions of sufficient strength and frequency to effect progressive effacement and dilation of cervix between 20 to 37 weeks of gestation

Early preterm labour

Cervix is dilated > 1 cm but <3 cm, >80 % effaced Documented uterine contractions with no cervical change

Advanced preterm labour

If the cervix is >80% effaced and cervical dilatation is 3 cm or more Prematurity is classified in three groups according to gestational age:

-            Severe prematurity when birth occurs <30 weeks

-            Intermediate prematurity when birth occurs between 30-34 weeks

-            Late or mild prematurity when birth occurs between 34-37 weeks

Symptoms

1.      Uterine activity (painful or painless uterine contractions)

2.      Pelvic pressure

3.      Menstrual-like cramps

4.      Watery vaginal discharge

Signs

1.      Regular uterine contractions with or without pain at least one in every 10 mm

2.      Dilation >2cm and effacement (80%) of the cervix

3.      Length of cervix (measured by TVS<2.5CM

4.      Show

5.      Bulging membrane

6.      Rupture of membrane

Prevention of preterm birth

Primary prevention

1.      Prevent pregnancy in teenagers

2.      Prevent smoking and illicit drug use

3.      Prevent RTI/STI; treatasymtomaticbacteriuria

4.      Access of family planning method to prevent unwanted and frequent delivery

5.      Pre-conceptional counselling

6.      Improve nutrition and general health of woman

7.      Decrease factor causing stress and give adequate rest SECONDARY PREVENTION

It includes identification of women who are at PTB and their close surveillance it includes screening tests for early defection and their treatment

ACOG guidelines

Major recommendations

·        There are no clear 1st line tocolytic drugs to manage preterm labour

·        Circumstances & physician's preference should dictate the treatment

·        Antibiotics do not appear to prolong the gestation & should be reserved for gpB streptococcal prophylaxis in patients in whom delivery is imminent.

·        Neither maintainance treatment with tocolytic nor repeated acute tocolysis improve the perinatal outcome

·        Tocolytics may prolong pregnancy for 2 to 7 days, which allow steroid administration & transfer to tertiary care centre with good NICU

LEVEL B recommendations

·        Cervical USG Metal fibronectin have good negative predictive value, thus either approach or combined maybe helpful in determining patients who need tocolyfics

·        Amniocentesis may be used in women in preterm labour to assess fetal lung maturity & intraamniotic infection.

·        Bed rest and hydration do not appear to improve the rate of preterm birth & should not be routinely recommended

Investigations

·        Full blood count

·        Urine for routine analysis, culture and sensitivity

·        Cervicovaginal swab for culture and fibronectin

·        Ultrasonography for fetal well being, cervical length and placental localisation

·        Serum electrolyte and glucose levels when tocolytic agents are to be used

Management

The following regime may be used to arrest preterm labour -

·       Bed rest

·       Adequate hydration

·       In utero transfer

·       Tocolyfic agents

1.    Bed rest

Patient to lie on left lateral position though the benefits are doubtful

2.    Hydration and sedation/bed rest

In a study woman received 500 ml of crystalloid over 30 min and 8-10 mg of morphine i/rn had outcome similar to bed rest. So it gives no added advantage

3.    ln utero transfer

If local facilities are inadequate to treat preterm labour an inuter transfer is better than exutero transfer as the uterus is better transfer incubator.

5.      Short Course of Tocolytic therapy Indications

a)       gestation <34 weeks

b)        no fetal ormaternal compromise

c)       in utero transfer Contraindications to tocolysis

a)    Fetal demise or anomalies incompatible with life

b)    Fetal distress

c)     Severe bleeding or abruptio placentae

d)    Severe IUGR

e)    Chorioarnnionitis

f)      Cervix > 3cm. Dilated

g)    Fetal maturity

h)    Maternal hemodynamic instability

i)      PPROM

Tocolysis has not be shown to improve perinatal outcomes. It prolongs pregnancy by at least 48 hrs allowing administration of betamethasone and shifting the patient to a centre equipped with better neonatal facility

Regimes for Tocolysis

·        Calcium channel blockers

·        B-sympathomimetics

·        Non steroidalanti inflammatory agent

·        Oxytocin receptor antagonist

·        Nitric oxide donors

Calcium channel blockers (nifedipine)

It is calcium channel blocker that causes smooth muscle relaxation and is used for the t/t of chronic hypertension

•            The loading dose is 20-30mg and maintenance dose is 10-20mg every 6 hr (max dose is 160 mg)

•            It is best 1st line tocolytk agent available in market because of easy availability, cheaper cost, ease of administration and fewer side effects than b-sympathomimetics

Side effect

Headache, tachycardia, palpitation, flushing, fatigue, dizziness, nausea, constipation and edema

Maternal contraindication of use of nifedipine

o   Hypotension (SBP<90mm of Hg)

o   Known allergy to nifedipine

o   Cardiac dis (CCF,aortic stenosis)

o   Concurrent    use    of    salbutamol,    glycerol                         trinitrate, other               anti hypertensive use, hepatic dysfunction

o   Caution with usage withMgSO4 because significant hypotension with neuromuscular blockage can occurs

Beta-adrenergic agonists

Ritodrin

For intravenous administration the initial dose is 1 OOug/min The dose is increased by 50 ug/min until the contractions stop Max dose is 350ug/min

Once labour is inhibited ,maintenance dose is for 12 hr

Fluid is restricted to 2.51/24 h Infusion of B agonist resulted in frequent, and at times serious and fatal side effects

Pulmonary edema is a special concern.lt causes increased capillary permeability, disturbance of cardiac rhythm and Ml.

Terbutaline

B agonist commonly used to forestall labour

5 mg of terbutaliné is dissolved in 500 ml of RL and started at 5ug/min

Dose is increased gradually by 5ug/min every 10 to 20 min until uterine contractions stop

The max dose is 30ug/min.

Then s/c admn 0.25-0.5mg for every 2 to 4hr for 12 hr.

A maintenance dose of 2.5-5mg orally given 4-6 times daily Side Effects of B Mimetics

Headache,    Palpitations,    Tachycardia,    Pulmonary                                   edema,              Hypotension, Cardiacfailure,

Hyperglycemia, ARDS, Hyperinsulinemia, Lactic acidosis, Hypokalemia Contraindication to betamimetic agents

Maternal cardiac rhythm disturbance, Poorly controlled DM, Thyrotoxicosis, Sickle cell ds, chorioamniotis

MAGNESIUM SULPHATE

Loading dose 4 g over 15-20 mm Followed by infusion at 1-2 gm/hr

Serum levels of 8 to 10meq/l required for tocolysis

Causes sedation, ↓ analgesic requirements

Modest prolongation of bleeding time due to effect on platelet aggregation by antagonizing the effects of Ca++

SIDE EFFECTS OF MgSO4

Flushing, maternalhypothermia, Perspiration, Headache, paralytic ileu, Muscle weakness

Contraindications to Mg SO4

Hypocalcemia, Renal failure Myasthenia gravis INDOMETHACIN

50 mg PO/PR followed by 25 mg 6 hrly for 48 hrs

Limit course of therapy to less than 72 hr and administer only before 32 week gestation to minimize neonatal side effects

No cardiovascular side effects like other agents

Indomethacin can be used as second stage tocolytic agent in early gestational age PTL

It may be 1st line tocolytic in associated polyhydramnios (to have renal effects of indomethacin)

Side Effects

GI    bleeding,   Asthma,    thrombocytopenia,    cause                    premature closure     of ductusarteriosus in utero

ATOSIBAN

Given in IN infusion (300ug/min)

CVS effects are much less than b mimetics It is expensive and not yet available in India

NITROGLYCERIN

Preferred way is to give by transdermal patch, manufactured to release a specific amount of medication b/w 0.1 -0.8mg/hr. Minimal side effects include hypotension and headache

Steroids to Accelerate Fetal Lung Maturity Betamethasone:12 mg. IM in 24hx2 dose

Dexamethasone: 6 mg, IM in 12h x4 doses Effect of glucocorticoids on fetal lungs lasts no longer than 1 week

Rescue weekly repeat doses of betamethasone should not be given because of neonatal side effects

Repeat doses interfere with CNS myelination, decrease birth weight, decrease head circumference with increase in risk of cerebral palsy

Contraindication tocorticosferoids

•                          fetal, neonatal deaths

•                          Chorioamnoitis

•                          Maternal tuberculosis

•                          Porphyria

•                          Pregnancy> 34 weeks

•                          Maternal or fetal infection

*Refer Patient to higher centre for further management.

ROLE OF PROGESTERONES

PROGESTERONE maintains uterine quiescence and blocks the labour initiation Benefit is primarily in reduction of birth before 34 weeks

-  FDA of USA has recently approved administration of weekly injections of 17- hydroxyprogesterone acetate for prevention of recurrent preterm birth

-   ACOG2008c has concluded that progestrone therapy should be limited to women with documented h/o previous spontaneous birth at <37 weeks

Strategies for prevention of PTL and PTB -

Use of tocolyfic as maintenance therapy after primary treatment Till date available evidence does not support the use of oral B-mimetic drugs and other focolyfic drugs for maintenance therapy after threatened PTL

Management of women presenting with threatened or actual preterm labour

Once diagnosis is confirmed clinical exam with appropriate investigation of maternal and fetal condition should be done:

-  Ultrasound is done to know about fetal number, estimated fetal weight, fetal morphology along with presentation ,liquor vol and placental sitefwb ,along with umblical vessel doppler assessment and fetal activity along with fetal breathing movement which are suppressed in women with PlL

Follow up

Search for cause /precipitating factors Establish plan for future pregnancy Provide long term follow up for neonate

Key Message

1.                Corticosteroids should be given to the mother to reduce the risk of neonatal respiratory distress syndrome.

2.                In-utero transfer of the mother for delivery in a unit where appropriate neonatal care can be provided

3.                Tocolyfic drug can be used for a short period unless contraindicated

4.                Antibiotic in cases with infection

5.                Careful    intrapartum    monitoring,    minimal    trauma                 &                        involvement  of neonatologist during delivery are essential

6.                Vaginal delivery is preferred unless caesarean is indicated for obstetric reasons