1. Preterm Labour
Dr Fatima Patel

2. Summary
• Introduction
• Definition of preterm labour
• Risk factors for preterm birth
• Pathophysiology
• Prevention
• Complications
• Management
• Followup

3. Introduction
• Certain dates vital either LMP, early USS
• More than 50% of patients with possible
threatened preterm labour deliver after 37
weeks
• Some medications e.g. tocolytics can be
harmful to mother
• Identification of risk factors and prevention
is the aim

4. Definition and diagnosis
• The diagnosis of PTL is generally based
upon clinical criteria of regular, painful
uterine contractions accompanied by
cervical dilation and/or effacement
between 20 and 36 weeks and 6 days
• ‘Preterm’ means we know her gestational
age accurately

5. Gestational age estimation
• LMP based on sure dates (menstrual calender),
regular cycle, not on contraception within last 3
months; Naegle’s rule based on 28 day cycle:
adjust if more or less than.
• May have to change if first trimester scan is
>5days different (CRL) or less than 20 weeks
scan >7 days different (HC)
• Once determined not for change as later scans
reflect size of baby

6. Special Investigations
• Fetal Fibronectin (FFN): swab taken from
the post vaginal fornix at speculum
examination and tested for FFN. Highish
false positive. Value lies in a negative test
• Transvaginal ultrasound for cervical
length(TV CL) measurement: if TVCL is
>2cm then the chances of delivery less
than 35 weeks are small.

7. Risk Factors for PTL
Non-modifiable risk factors
• Prior preterm birth
• African-American race
• Age <18 or >40 years
• Poor nutrition/low prepregnancy 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)
• Periodontal disease? Vaginal bleeding? Excessive uterine activity

8. Risk Factors contd
Modifiable risk factors
• Cigarette smoking
• Substance abuse
• Absent prenatal care
• Short interpregnancy intervals
• Anemia
• Bacteriuria/urinary tract infection
• Genital infection
• ? Strenuous work? High personal stress

9. Pathophysiology of PTL
• Premature activation of the maternal or
fetal hypothalamic-pituitary-adrenal axis
• Exaggerated inflammatory response/
infection
• Decidual hemorrhage
• Pathological uterine distention
These processes may be initiated long
before PTL or PPROM are diagnosed
clinically.

10. Prevention – potentially effective
• Cessation of smoking, avoid cocaine use
• Decrease the rate of multiple gestation from ART
• Diagnose and treat asymptomatic bacteriuria
• Decrease occupational fatigue
• Nutritional intervention
• Avoid short interpregnancy interval ‘ideal’ > than 12
months but not >48 months
• Progesterone
• Inhibition of acute preterm labour
• Cervical cerclage

11. Unproven
• Diagnosis and treatment of genital tract
infection
• Treatment of periodontal disease
• Bed rest and hospitalisation
• Abstinence
• Prophylactic tocolytics
• Antibiotics
• Thyroid hormone, social support

12. Management
• treat only the women with true preterm
labour and a real risk of preterm birth by
knowledge of TVU CL and FFN
• If CL is <20mm then admit, steroids,
tocolysis
• If CL is 20-29mm and FFN positive then
above management, if FFN negative then
discharge; if contractions continue
consider prolonged observation and ?
repeat TVCL
• If CL >30mm then discharge

13. Optimisation of foetal status
• Transfer: to appropriate level hospital
usually with level 3 NICU
• Corticosteroids for foetal maturity between
24 and 34 weeks gestation. Single course
of betamethazone (pending ASTEROID
trial results) 11.4mg twice IMI 24 hours
apart. A single rescue dose can be given if
first course given before 28 weeks
gestation and more than 14 days later with
appropriate counselling 13

14. Tocolysis
• The goal is to prevent imminent preterm
birth in order to have sufficient time to
administer steroids and to have sufficient
time if appropriate to allow for in utero
transfer to hospital with NICU
• Usually nifedipine is first line
• Magnesium sulphate has been shown to
significantly decrease cerebral palsy in 5
trials
14

15. Complications
• cerebral palsy
• cognitive defects (e.g. low IQ)
• school difficulties
• behavioural problems
• diminished long term survival and
reproduction
15

16. Follow-up
• Post partum counselling on preventive
strategies are important after one episode
of preterm labour and birth.
16