A quick view on Preterm Labour and its causes.

1. Type to enter a caption.
Preterm LabourIntroduction and Causes
By Humna Anis

2. Definition
• Preterm labour is defined by WHO as Onset of
Labour prior to the completion of 37 weeks of
gestation, in a pregnancy beyond 20 weeks of
gestation.
• Preterm labour is considered to be established if
regular uterine contractions can be documented
atleast 4 in 20 minutes or 8 in 60 minutes with
progressive change in the cervical score in the
form of effacement of 80% or more and cervical
dilation>1 cm.

3. • If uterine contractions are perceived in the
absence of cervical change, the condition is
called “Threatened Preterm Labour”.
• Nearly 50-60% of preterm births occur following
spontaneous labour.
• 30% due to preterm premature rupture of
membranes.
• Rest are iatrogenic terminations for maternal or
fetal benefit.

4. Pathogenesis
•Preterm labour maybe Physiological or Pathological.
•As parturition nears, the fetal adrenal axis becomes more sensitive
to ACTH and there is an increased production of Cortisol.
This stimulates 17-hydroxylase in the trophoblast resulting in
decreased progesterone secretion.
The reversal of estrogen-progesterone ratio
Increase in Prostaglandin Formation
Initiation of Labour

5. Classification
• For reasons related to aetiology, outcome and
recurrence risk, preterm births should be divided
into 3 gestational periods:
• Mildly preterm births (32+0 to 36+6 weeks)
• Very Preterm births (28+0 to 31+6 weeks)
• Extremely preterm births (24+0 to 27+6
weeks)

6. Aetiology and Risk Factors
• Obstetric Complications
• Racial Factors
• Demographic Factors
• Psychological Factors
• Past Obstetric History
• Infection
• Genetic Factors

7. Obstetric Risk Factors
•Conditions that cause over distension of uterus: Multiple
Pregnancies, Hydramnios.
•Preterm Premature Rupture of Membranes (PPROM)
•Idiopathic Preterm Labour
•Pre eclampsia
•Antepartum Hemorrhage
•Second Trimester bleeding not associated with Placental Causes
•Iatrogenic Preterm Termination for pre-eclampsia, fetal distress,
IUGR, Abruptio Placenta and uterine fetal death.

8. Racial Factors
• Black women have twice the risk compared to
whites.
This maybe explained by multiple factors like
socioeconomic status, medical disorders and
genetic predisposition.

9. Demographic Factors
• Women with low BMI and poor maternal weight gain in
pregnancy are at increased risk.
• Age-women younger than 17 and older than 35 yrs.
• Poor education
• Women living alone
• Minimal or no prenatal care
• Low socioeconomic status
• Multiple sexual partners

10. Psychsocial Factors
• Anxiety
• Stress
• Depression
• Negative life events
• Perception of racial discrimination and domestic violence
• Excessive alcohol intake
• Smoking

11. Past Obstetric History
• Previous h/o preterm birth (17-20% recurrence risk) or
second trimester pregnancy loss.
• 3 or more abortions (may result in cervical
incompetence)
• DES (diethylstilbestrol) exposure
• Conceptions following IVF
• Cervical incompetence (10-20% second trimester
losses)

12. Infection
• Result in 50% spontaneous preterm births.
• Asymptomatic bacterial vaginosis
• Trichomonas vaginalis
• Chlamydia trachoma’s
• Ureaplasma Urealyticum
• Mycoplasma hominis
• Asymptomatic bacteriuria
• Systemic Infections like pyelonephritis, pneumonia, acute
appendicitis.

13. Genetic
• Important component of idiopathic group.
• Single gene polymorphisms of cytokines in
both mother and fetus may be responsible.
• Polymorphisms involving TNF alpha-308, IL-
1Beta and IL-6 have been most consistently
associated with spontaneous preterm labour
and preterm birth.

14. Clinical Features of Preterm
Labour
• HISTORY:
• Always check the dating of pregnancy by
reviewing menstrual history and prior USG
examinations.
• Vague complaints such as increased discharge,
pelvic pressure or low backache.
• Contractions accompanied by advanced dilation
(>3cm), ruptured membranes or significant
vaginal bleeding.

15. • EXAMINATION:
• Abdominal examination will reveal the
presence of uterine tenderness, suggesting
abruption or chorioamnionitis.
• Speculum examination may reveal: pooling
of amniotic fluid, blood and/or abnormal
discharge.
• A visual assessment of cervical dilation.

16. Prediction of Preterm Labour
(Investigations)
• The two most promising markers currently
available are:
1.Fetal Fibronectin levels
2.Ultrasound assessment of cervical length

17. Fetal Fibronectin (fFN)
• It is an extracellular glycoprotein secreted by the chorionic tissue at
maternal-fetal interface.
• It is present in amniotic fluid, placental tissue and decidua basalis.It
acts as a biological glue which binds blastocyst to endometrium.
• It can be normally present upto 20-22 weeks.
• Therefore presence of fFN between 27-34 weeks can provide
important marker of preterm labour.
• Swabs can be taken from ectocervix or post vaginal fornix. ELISA
with FDC-6 monoclonal Ab is used to detect fFN.
• A cut-off of 50ng/ml is considered positive.

18. Length of Cervix
• Cervical insufficiency is defined as cervical
changes in absence of uterine contractions.
• Cervix can be assessed visually or by USG.
• A reduction in cervical length of >6mm between
2 Ultrasounds have higher risk.
• Funneling (internal os diameter >= 5mm) is also
independent risk factor.

19. Repeat Vaginal
Examination
• Repeat in 1-4 hours should be considered
essential in the absence of specialised tests. The
interval between assessments should be guided
by the severity of the symptoms.