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Phase 3a Obstetrics > Pre-term birth > Flashcards

Pre-term birth Flashcards

1
Q

Define premature infant

A

Born before 37 weeks

they can be small or adequate for their gestational age

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2
Q

Define low birthweight infant

A

<2500g at birth regardless of gestational age (5.5 pounds)

They could be appropriate for gestational age in which case they are premature

Or could be small for gestational age and either premature or term

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3
Q

What are the long-term sequelae of prematurity?

A

developmental delay
visual impairment
chronic lung disease
cerebral palsy

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4
Q

What advancements have meant that premature babies are able to survive?

A 
Antibiotics 
Antenatal steroids 
Artificial surfactant 
Ventilation
Nutrition
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5
Q

What are the causes of preterm delivery?

A

Spontaneous

  • pre-term labour
  • premature preterm rupture of membranes
  • cervical weakness
  • amnionitis

Iatrogenic - medically indicated

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6
Q

What is the trend in the percentage of babies born prematurely or LBW over time?

A

Has increased since 1990

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7
Q

What are the risk factors for pre-term birth (ie spontaneous pre-term labour)?

A

Race
Previous pre-term birth
Genital infection eg bacterial vaginosis
General infection - UTI, pylonephritis, appendicitis
Cervical weakness
Antepartum haemorrhage and other vaginal bleeding
Multiple pregnancy
Socioeconomic status
Smoking
IVF

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8
Q

Describe the pathophysiology of choriodecidual bacterial infection and preterm birth

A

There is both a maternal and foetal response to the infection

  1. The fetus has increased cortisol production and the mother has increased cytokines and chemokine production
  2. Both of these result in increased prostaglandins
  3. Increased myometrial contractions
  4. Increased metalloprotease production
  5. Cervical ripening, choriamnion weakening and rupture
  6. preterm delivery

So in a nutshell:

  • fetal and maternal response to infection
  • increased prostaglandins
  • uterine contractions
  • metalloproteases weaken the chorioamnion and cause cervical ripening
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9
Q

What are the three categories of prevention of pre-term birth?

A

Primary
Secondary
Tertiary

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10
Q

What are the approaches to primary prevention of pre-term birth?

A 
(not demonstrated to be effective yet) 
Smoking cessation
STD prevention
Prevention of multiple pregnancy
Variable work schedules
Planned pregnancy
Physical and sexual activity advice
Cervical assessment at 20-26 weeks
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11
Q

What does secondary prevention mean in terms of pre-term birth?

A

Identifying those pts at increased risk of PTB and providing prophylaxis and suveillance

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12
Q

Which women are screened for PTB?

A

High risk:

  • 2nd trimester miscarriage
  • previous early 3rd trimester delivery (before 32 weeks)
  • PPROM (before 32 weeks)
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13
Q

How are high risk women screened and managed for PTB as part of secondary prevention?

A
  1. High vaginal swab at booking (11 weeks) for bacterial vaginosis - treat with single dose 2g metronidazole
  2. Transvaginal cervical ultrasound at 14 weeks, then repeat every 2 weeks till 28 weeks
  3. Qualitative Fetal fibronectin test
  4. progesterone - IM injection or pessary
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14
Q

What does a transvaginal ultrasound screen for?

A

Opening of the internal os and resulting reduced length of the cervical canal

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15
Q

How long is a cervix that is classified as a threatened preterm labour cervix?

A

<3cm

normal is at least 3 cm

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16
Q

What is measured in the screening transvaginal ultrasound?

A

Cervical length - distance between internal and external os

Look for funnelling - ie open internal cerivcal os, if present, measure the funnel length

17
Q

What is fetal fibronectin (fFN)?

A

Extracellular matrix protein found in choriodecidual interface

18
Q

What is the significance of fetal fibronectin (fFN)?

A

It is a signal that the baby is coming…
Abnormal finding after 20 weeks
As it indicates disruption of attachment of membranes to decidua

its normal for it to be present before labour - as the baby is coming

19
Q

How do you test for fFN?

A

high vaginal swab of the posterior fornix

20
Q

What are the reasons for a false positive fFN?

A

Cervical manipulation ie vaginal examination
Sexual intercourse
Lubricants
Bleeding

21
Q

What is the principle of tertiary prevention of pre-term labour?

A

Treatment after diagnosis of pre-term birth

22
Q

What are the clinical signs of pre-term labour?

A

Persistent contractions - painless or painful
Intermittent abdo cramping, pelvic pressure or back pain
Increased or change in vaginal discharge
Vaginal spotting or bleeding

23
Q

What are the approaches to tertiary prevention of pre-term birth?

A
  1. Prompt diagnosis and referral
  2. Antibiotics
  3. Tocolytic (Atosiban: an oxytocin receptor blocker) - tocolytics suppress uterine contractions
  4. Steroids - for maturation of babies lungs
24
Q

What is the definition of preterm labour?

A

Persistent uterine activity AND change in cervical dilatation and/or effacement

25
Q

How would you examine a pt presenting with possible pre-term labour?

A
  • sitting pulse and BP - maternal infection

- temp - for chorioamnionitis (is a contraindication of suppression of pre-term labour)

26
Q

What investigations would you do for a pt presenting with possible pre-term labour?

A
  1. FBC - CRP and WBC - for chronioamniotis
  2. CTG
  3. Sterile speculum examination
    - vaginal pH - bacterial vaginosis
    - High vaginal swab - bacterial vaginosis, fetal fibronectin
    - Endocervical swabs - chlamydia and gonorrhoea
    - Low or high vaginal swab - group B strep
  4. Transabdominal USS
    - plancental location
    - amniotic fluid volume - has she leaked liqour
    estimated fetal weight and presentation - in case she goes into labour
    - fetal well being - is the baby alive or not
  5. Transvaginal USS
    - cervical length <3cm and contractions = pre-term labour
  6. cervical examination
    - assess dilatation and effacement
27
Q

When do you test for group B strep in pregnancy?

A
  • ruptured membranes
  • pre-term labour
  • vaginal discharge
28
Q

Why is it important to treat group B strep in pregnancy?

A
  • can cause chroiamnitis and neonatal sepsis, pneumonia and meningitis and neonatal death particularly in pre-term babies or in distressed babies (eg placental insufficiency)
  • can cause pre-term labour if there are ruptured membranes

Phase 3a Obstetrics (11 decks)

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