recent available Guideline Recommendations
Preterm birth (PTB), defined as delivery at less than 37+0 week’s gestation, is a common
complication of pregnancy, affecting around 8% of births in England and Wales.
Extremely preterm – birth before 28 weeks
very preterm – 28-32 weeks
moderately preterm- 32-34weeks
late preterm -34- 37
Risk factors for preterm birth
- Previous preterm birth
Previous PTB is the most significant risk factor for PTB. This association is modified by
three risk factors:
- the number of prior PTBs
- the gestational age at which the previous birth(s) occurred, and
- the order in which the prior PTB(s) occurred.
For example, the risk of PTB in the current pregnancy, - with one previous PTB, is 15-20%,
after - two PTBs it is 35-40% and
- with one preterm and a subsequent term birth the risk is
reduced to 10-15%.
2. Abnormal vaginal flora
The imbalance of microbial subpopulations seen in bacterial vaginosis (BV), predominance
of anaerobes and deficiency of lactobacilli is associated with an increased risk of PTB.
.
consider treatment of BV if identified whilst performing routine screening.
Neisseria gonorrhoeae and Chlamydia trachomatis may also
trigger an inappropriate inflammatory response leading to labour.
Group B streptococcal
colonisation is normally seen in up to 25% of inner-city populations and is not an indication
for antepartum treatment unless accompanied by symptomatic discharge or bacteriuria
3. Urinary tract infection (UTI)
UTI including asymptomatic bacteriuria, cystitis, and pyelonephritis is associated with PTB.
4. Systemic bacteraemia
Both acute (e.g. pyelonephritis, appendicitis, pneumonia and dental abscesses) and chronic
(cystic fibrosis) bacteraemias are associated with PTB.
5. Cervical compromise
It may arise following large loop excision of the
transformation zone (LLETZ), where the amount of tissue removed is >10mm in depth,
multiple dilatations of the cervix,
hysteroscopic procedures where the cervix has been dilated
up to or beyond Hegar 10,
or in conjunction with Mullerian variants (alterations in uterine
size/shape such as unicornuate or bicornuate uteri).
6. Uterine capacity
Conditions that increase uterine distension or interfere with uterine capacity such as
fibroids,
polyhydramnios,
multiple pregnancy,
or as a consequence of Mullerian variants are risk factors for PTB
7. Placentation
Antepartum haemorrhage and/or persisting extrachorionic haemorrhage due to abnormal
placentation, with chronic and repeated bleeding, is also a recognised risk factor for PTB
8. Social factor – Smoking , Maternal Age, Domestic Violence
This doubles the risk of PTB
Young women (<18 years) have an increased risk of PTB.
domestic violence and/or other social pressures should be directly
counselled and referred for specific support through our local pathways.
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