Preterm labor occurs after viability but before 37 weeks of gestation, with causes being multifactorial, including hormonal changes and infection-related inflammation. Risk factors include demographic aspects, previous preterm births, maternal health, and psychological factors, while diagnosis relies on clinical symptoms and ultrasound. Management may involve cerclage, tocolytics, and prophylactic measures to delay delivery and improve neonatal outcomes.

1. PRETERM LABOR

2.  Preterm labor is onset of labor after period of
viability and before completing 37wks with
gestation .
 Early preterm: delivery between 28wsk to
34wks
 Late preterm; between 34 and 37 completed
weeks. 70% of all preterm births.
PRETERM LABOR

3.  Mechanisms that lead to the onset of preterm
labor are complex and multifactorial, but it is
likely to occur as a result of the concomitant
activation or a cascade of the following events;
◦ Functional progesterone withdrawal
◦ Increase in corticotrophin-releasing hormone
◦ Premature decidual activation
◦ Increased prostaglandin production
◦ Oxytocin initiation
◦ Increased cytokine production
Pathophysiology

4.  Spontaneous unexplained preterm labor with
intact membranes
 Idiopathic preterm premature rupture of
membranes (PPROM)
 Delivery for maternal or fetal indications, and
 Twins and higher order multifetal births.
Main direct reasons for preterm
births

5. RISK FACTORS FOR PRETERM LABOR

6.  DEMOGRAPHIC : Age (<18yr or > 35yr)
low socioeconomic status
low pre pregnancy weight
 MULTIFETAL PREGNANCY; Uterine stretch increases
gap junction proteins, PGs synthesis, receptors for
oxytocin and specific contraction associated proteins
(CAPS).
 Hydramnios
 Placental infarction,
 IDIOPATHIC
RISK FACTORS FOR PRETERM BIRTHS

7.  INTRAUTERINE INFECTIONS; trigger preterm
labor by activation of the innate immune system. In
this hypothesis, microorganisms elicit release of
inflammatory cytokines such as interleukins and
TNF-α, which in turn stimulate the production of
prostaglandin and/or matrix-degrading enzymes.
Prostaglandins stimulate uterine contractions,
whereas degradation of extracellular matrix in the
fetal membranes leads to preterm rupture of
membranes.
 UTI , Bacterial vaginosis have also been seen to
increase risk of preterm labor

8. FETAL ANOMALIES; In a secondary analysis of
data from the First- and Second-Trimester
Evaluation of Risk (FASTER) Trial, it was found
that birth defects were associated with preterm
birth and low birthweight
PRIOR PRETERM BIRTH
A major risk factor for preterm labor is prior
preterm delivery. Increases risk 3 folds

9.  Uterine anomalies: Cervical incompetence,
malformation of uterus
 Cigarette smoking, inadequate maternal
weight gain, and illicit drug use have
important roles in both the incidence and
outcome of low-birthweight neonates
 Overweight and obese mothers have an
elevated risk of preterm birth
Maternal factors

10. WORK AND PHYSICAL ACTIVITIES
There is some evidence, that working long hours
and hard physical labor are probably associated
with increased risk of preterm birth.
PSYCHOLOGICAL FACTORS such as depression,
anxiety, and chronic stress have been reported in
association with preterm birth

11. INTERVAL BETWEEN PREGNANCIES
 Short intervals between pregnancies have been
known to be associated with adverse perinatal
outcomes.
 Intervals < 18 months and > 59 months were
associated with increased risks for both
preterm birth and small-for gestational age
newborns

12.  Preterm labor is primarily diagnosed by
symptoms and physical examination.
 Ultrasound is used to identify asymptomatic
cervical dilation and effacement.
DIAGNOSIS

13. Regular uterine contractions with or without
pain (at least 4 in 20 minute) along with cervical
changes showing following :
 Dilatation (1 cm or > 1 cm ) and effacement
(80% or more )of the cervix;
 Length of the cervix (measured by TVS) < 2.5
cm and funneling of the internal os.

14.  Hemogram , LFT, RFT , SE
 Urine for routine analysis, culture and
sensitivity
 High vaginal swab for culture
 Ultrasonography for fetal well being, cervical
length and placental localization
INVESTIGATIONS

15. 1. Cervical Cerclage
 There are at least three circumstances when cerclage
placement may be used to prevent preterm birth. Two
are done prophylactically, and a third is done for
treatment. The first prophylactic cerclage is used in
women who have a history of recurrent midtrimester
losses and who are diagnosed with cervical
insufficiency. The second prophylactic cerclage is for
women identified during sonographic examination to
have a short cervix. The third indication is “rescue”
cerclage, done emergently when cervical incompetence
is recognized in women with threatened preterm labor.
PREVENTION OF PRETERM LABOR

16. 2. Prophylaxis with Progestin Compounds (17-
hydroxyprogesterone)
 Progesterone levels in most mammals fall rapidly
before the onset of labor. This is termed progesterone
withdrawal and is considered to be a parturition-
triggering event. During human parturition, however,
maternal, fetal, and amnionic fluid progesterone levels
remain elevated with no decline. It has been proposed
that human parturition involves functional
progesterone withdrawal mediated by decreased
progesterone activity of progesterone receptors. It
follows conceptually that the administration of
progesterone to maintain uterine quiescence may block
preterm labor.

17. (1) Glucocorticoids to the mother to reduce
neonatal RDS, IVH( intraventricular hemorhage)
and NEC(necrotizing enterocolitis).
Betamethasone (Betnesol) 12 mg IM 24 hours
apart for two doses or dexamethasone 6 mg IM
every 12 hours for 4 doses is given
(2) Tocolytic drugs to the mother for a short
period unless contraindicated
PRINCIPLES OF MANAGEMENT OF
WOMEN WITH PRETERM LABOR

18. (3) Antibiotics to prevent neonatal infection with
Group B Streptococcus (GBS)
(4) Careful intrapartum monitoring, minimal
trauma and presence of a neonatologist during
delivery
(5) Vaginal delivery is preferred, unless otherwise
indicated for cesarean birth

19. Primary purpose of tocolysis is to delay delivery
by atleast 48 hrs :
 To allow maximum benefit of steroids to
decrease incidence of RDS
 To delay delivery for in utero transfer to center
with adequate neonatal facilties
 To administer antibiotics to reduce neonatal
infections
Maintainence dose of tocolysis is not
recommended in current practice
TOCOLYSIS

20. Mechanism: Convert ATP into cAMP in the cell
causing decrease of the free calcium ion.
Drugs used: Isoxsuprine , ritodrine , terbutaline
Side effects :
 Mainly cardiovascular as increased heart rate and
hypotension, Chest pain in 1-2% from myocardial
ischemia.
 Increased liver and muscle glycogenolysis causing
hyperglycaemia and increase in insulin cause
hypokalaemia.
B-Adrenergic agonist
(B-sympathomimetic agent):

21. Mechanism:Compete with calcium for entry into
the cell at the time of depolarization so there is
decrease of intracellular calcium.
Side effect:
 Warm and flushing
 Respiratory arrest
 Fetal hypotonia due to decrease calcium
MAGNESIUM SULPHATE

22. Indomethacin is the most commonly used.
Side effects:
 Decrease fetal renal blood flow and cause
oligohydramniosis.
 Premature closure of ductus arteriosus which lead to
pulmonary Hypertension.
 Necrotizing enterocolitis.
PROSTAGLANDINS SYNTHETASE
INHIBITORS

23. Nifedipine:Inhibits the inward current of calcium
iron during the 2nd phase of the action
potential of uterine muscle
Side effects:
1- Headache 2- Hypotension
3-Flushing 4- Tachycardia
CALCIUM CHANNEL BLOCKERS

24. Atosiban
Expensive drug.
Side effects:nausea, dizziness, headache, and
flushing.
OXYTOCIN RECEPTOR ANTAGONISTS

25.  Maternal: Uncontrolled diabetes,
thyrotoxicosis, severe hypertension, cardiac
disease, hemorrhage in pregnancy, e.g.
placenta previa or abruption.
 Fetal: Fetal distress, fetal death, congenital
malformation, pregnancy beyond 34 weeks.
 Others: Rupture of membranes,
chorioamnionitis, cervical dilatation more than
4 cm
Contraindications of tocolytics

26.  If fetus is not compromised, the maternal
condition remains good and membranes are
intact;
 Bed rest; preferably in left lateral position
 Adequate hydration
 Prophylactic cervical circlage; for women with
prior preterm birth and short cervix in the
present pregnancy
 Tocolytic agents
MEASURES TO ARREST PRETERM
LABOR

27.  Braxton Hicks contractions; irregular,
nonrhythmical, and either painful or painless
 Urinary; acute cystitis, pyelonephritis,
nephrolithiasis
 Gatrointestinal: Constipation
D/D of Preterm Labor

28.  Prematurity;
 Chorioamnionitis from ascending infection if
>24hrs
 Cord prolapse specially when associated with
malpresentation with membrane rupture
 Placental abruption
 Neonatal sepsis, RDS, IVH and NEC in preterm
PROM
 Perinatal morbidities (cerebral palsy) are high
COMPLICATIONS OF PRETERM
LABOR

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