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Woman's Health > 6.4 Preterm labour > Flashcards

6.4 Preterm labour Flashcards

1
Q

What is definition of preterm labours?

A

all deliveries between 24+0 to 36+6 weeks with a foetus weighing >500g → subclassified based on gestational age

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2
Q

what gestational is considered mildly preterm ?

A

32+0 to 36+6 weeks

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3
Q

what gestational is considered moderately preterm ?

A

28+0 to 31+6 weeks

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4
Q

what gestational is considered extremely preterm ?

A

24+0 to 27+6 weeks

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5
Q

when is term delivery?

A

labour occurring ≥37+0 weeks and <42+0 weeks of gestation

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6
Q

when is foetal viability?

A

from 24 weeks of gestation onwards (occasionally survive at 23 weeks)
o Survival increases with gestational age (8% at 23 weeks, 78% at 26 weeks)

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7
Q

When is resuscitation not offered?

A

Below 23+0 weeks

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8
Q

when is resuscitation based on parent’s wishes?

A

23+0 to 23+6 weeks

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9
Q

when is resuscitation offered to all neonates?

A

From 24+0 weeks

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10
Q

what is still birth?

A

Foetal death after 24 weeks gestation

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11
Q

what is perinatal mortality?

A

Still births + neonatal deaths through 28 days of life (per 1000 total births → does not need to be live births)

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12
Q

what is infant mortality?

A

Deaths among live born infants before 1 year of age (per 1000 live births)

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13
Q

what is perinatal morbidity?

A

Specific diseases or conditions related to immaturity of various organ systems

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14
Q

what are factors affecting outcome of preterm birth?

A

The above outcomes are influenced by the following factors:
• Gestational age (better if older)
• Birth weight (<500g is associated with extreme prematurity, significant morbidity & mortality)
• Foetal weight (singleton vs multiple gestation)
• Geographic location (proximity to neonatal care unit, efficiency of care)
• Maternal/foetal conditions that led to the preterm birth

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15
Q

what are the immeidate complications of preterm labour?

A
  • Respiratory distress syndrome (RDS) (most common complication)
  • Intra-ventricular haemorrhage (IVH)
  • Bronchopulmonary dysplasia (BPD)
  • Patent ductus arteriosus (PDA)
  • Necrotising enterocolitis (NEC)
  • Retinopathy of prematurity (ROP)
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16
Q

What are the long term complications of preterm labour?

A

Prematurity is associated with several major lifetime consequences including:
• Chronic lung disease
• Grade 3 or 4 IVH associated with cerebral palsy
• Visual & hearing impairment
• Neurosensory impairment, reduced motor & cognitive performance, academic difficulties

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17
Q

What are spontaneous causes for preterm delivery?

A
  • Idiopathic PTD (40%) → spontaneous onset
  • Preterm premature rupture of membranes (PPROM) (40%) → rupture of amnion & chorion membranes before onset of labour at <37 weeks gestation
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18
Q

what are acquired causes for preterm delivery?

A

• Iatrogenic causes (20%) → delivery undertaken for maternal or foetal indications (benefits of delivery > continuation of pregnancy

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19
Q

The exact pathophysiology of PTL is unknown but the causes are multifactorial:
• Common pathway: activation of _____________ & release of _____________ → myometrial contraction, cervical dilatation, membrane rupture
• Risk factors: stress, infection, haemorrhage, uterine distension, cervical incompetency, undernutrition

A

matrix metalloproteinases (MMPs);

prostaglandins

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20
Q

How does stress cause Preterm labour?

A

Psychological & physical stress causes release of catecholamines, cortisol, oxytocin → activation of HPA axis (CRH release) → increased prostaglandins → increased myometrial contractility

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21
Q

How does infection cause Preterm labour?

A

Inflammation causes cytokine, prostaglandin, MMP release → triggers uterine contractions, cervical dilatation, degradation of cervical plug → further colonisation of decidual space by more bacteria:
• Results in PTL ± chorioamnionitis

22
Q

How does haemorrhage cause Preterm labour?

A

Intrauterine haemorrhage causes release of thrombin → increased prostaglandins → myometrial contraction • Blood acts as a uterine irritant → triggers activity

23
Q

How does uterine distension cause Preterm labour?

A

Myometrial stretch causes expression of gap junctions → increased prostaglandins → uterine activity

24
Q

How does cervical incompetence cause Preterm labour?

A

Weakness of the cervix causes painless cervical dilatation before the onset of labour (rare cause in 2nd & 3rd trimesters):
• Most actually have a structurally normal cervix
• May occur after previous surgery to cervix (e.g. loop excision, cone treatment for cervical dyskaryosis, repeated surgical dilatation of cervix, cervical trauma, anatomical anomalies

25
Q

How does iatrogenic cause Preterm labour?

A

Induced for certain conditions (e.g. placental insufficiency, severe pre-eclampsia, signs of foetal distress

26
Q

what is intrauterine infections more likely to cause?

A

Intrauterine infections (e.g. bacterial vaginosis, GBS, gonorrhoea, chlamydia) are more likely to be contributory in earlier gestation

27
Q

what is extrauterine infections more likely to cause?

A

Extrauterine infections (e.g. UTIs, asymptomatic bacteriuria, systemic maternal infections like appendicitis, periodontal) cause cytokine release or haematogenous bacterial spread to uterus

28
Q

The trans-vaginal US (TVUS) measures ____________ & identifies any ______________:
• Optimal time:_______________
• Normal cervical length: ~35mm
o Cervical length <15mm is associated with 50% risk of delivery <32 weeks
o High negative predictive value → reassurance if _________________
• Indications for serial measurement: _________________
• Benefits: helpful in diagnosing PPROM → look for oligohydramnios in absence of foetal urinary tract abnormalities or intrauterine growth restriction (IUGR)

A

cervical length;

funnelling (dilatation of the internal os of the cervix & cervical shortening);

16 – 24 weeks gestation;

length >3cm at 24 weeks;

previous PTL, previous 2nd trimester loss

29
Q

Foetal fibronectin is a glycol-protein that acts as a glue between the foetal & maternal membranes and is found in vaginal secretions in early pregnancy:
• Typically absent from cervicovaginal secretions between 24 – 34 weeks gestation (due to ___________________)
o Presence indicates __________________ before the onset of labour → high risk for PTL
• Sampling method: swab from ___________________ → send for immunoassay

• Advantages:
o Higher positive predictive value for PTL in the following 7 – 10 days compared to digital examination → positive result indicates 50% risk of PTL
o High negative predictive value (up to 99%)

• False positives may result from the presence of alternative proteins (e.g. __________________)

A

fusion of chorion & decidual membranes;

disruption between membranes & decidua;

posterior fornix;

lubricating jelly, recent sexual intercourse, vaginal bleeding, PPROM

30
Q

how is preterm labour diagnosed?

A

Preterm labour is diagnosed based on the following criteria: 1. Gestational age <37+0 weeks 2

  1. Presence of regular uterine contractions (palpable or recorded on CTG) occurring every 5 – 10 min
  2. Evidence of cervical changes (effacement of 80% and dilatation of ≥2cm)

Note that preterm labour is not equivalent to preterm birth (only 8 – 24% presenting with symptoms of PTL will actually deliver prematurely)

31
Q

what are differentials for pre term labour?

A

UTI, uterine irritability, placental abruption, urinary incontinence

32
Q

what is needed for the history of preterm labour?

A
  • Establish accurate gestational age
  • Symptoms: abdominal pain (constant or intermittent), cramps, back pain, vaginal bleeding, spotting, show, leaking of liquor (amniotic fluid)
  • Complications: dysuria (UTI), diarrhoea (GI infections)
  • May also be asymptomatic or vague symptoms with cervical incompetence (vaginal discharge, cervical dilatation)
33
Q

what is needed for the examination of preterm labour?

A
  • General: pyrexia, tachycardia, hypotension → sepsis
  • Abdominal: contractions, tenderness
  • Speculum: cervical effacement, dilatation, membranes, blood, pooling of liquor (collection of amniotic fluid that can be seen in the vaginal fornix), offensive discharge (ruptured membranes/intrauterine infection)
  • *Avoid repeated vaginal examinations in PPROM!
34
Q

what is needed for the investigation of perterm labour?

A

The following investigations are used in patients with suspected PTL:
• FBC & inflammatory markers (CRP) → possible infection
• Urinalysis (dipstick & UFEME) & urine cultures → UTIs
• High vaginal swab → vaginal infections, GBS
• Actin partus/foetal fibronectin (FFN): rapid tests from week 20 until birth
• Obstetric US: assess presentation, liquor volume, placental position, estimated foetal weight, cervical length

35
Q

why is cardiotocography used to evaluate preterm labour

A

• Monitor foetal heart rate & uterine contractions

36
Q

How do tocolytics help with preterm labour?

A

Tocolytics are anti-contraction drugs used to suppress preterm labour, but tocolytics alone have not been shown to reduce rates of PTD or improve neonatal outcome: • Effect: prolongation of pregnancy for up to 48h → allow time for administration of antenatal steroids, in-utero transfer, maternal MgSO4

37
Q

what are examples of tocolytics?

A

nifedipine (Adalat), indomethacin, atosiban, salbutamol

38
Q

when is the optimum time to give tocolytics?

A

before 34 weeks (not recommended thereafter)

39
Q

what are the contraindications to tocolytics?

A

severe pregnancy-induced hypertension, antepartum haemorrhage with abruption, non-reassuring foetal status, overwhelming sepsis

40
Q

when is antibiotics needed for preterm labour?

A

The routine prescription of antibiotics is not recommended if membranes are intact: • Only initiated in labour to prevent neonatal GBS infection (in the event of PPROM or suspected chorioamnionitis

41
Q

what is the effect of corticosteroids?

A

Corticosteroids are administered to all women at risk of PTL between 24+0 to 34+6 weeks:
• Effects: reduction of neonatal death, RDS, NEC, cerebrovascular haemorrhage, and NICU admissions
• Mechanism of action: (1) stimulates pneumocytes to produce surfactant (2) aids the structural development of lung (3) intestinal maturation

42
Q

when is the optimum timing for coticoid steroids to be prescribed?

A

from 24h to 7 days before delivery

43
Q

why is magnesium sulfate prescribed for preterm labour?

A

Magnesium sulfate is a neuroprotective agent in preterm infants (dosing is unclear):
• Maternal administration may reduce risk of cerebral palsy in the preterm neonate (normally 14.6% at <28 weeks gestation & 6.2% between 28 – 31 weeks)

44
Q

how does cervical cerclage reduce the risk of preterm labour?

A

Cervical cerclage is an elective procedure that involves suturing around the cervix to provide mechanical support and keeps the cervix closed:
• Usually done by 14 weeks gestation; vaginal approach or abdominal approach (rare)
o Suture must be removed if labour occurs spontaneously or electively around 36+1 to 37+0 weeks

45
Q

what are the indications for cervical caclage?

A

history of 3 spontaneous preterm births or 2nd trimester losses or US finding of short cervix <25mm + history of PTL or 2nd trimester loss with singleton pregnancy

46
Q

what are the complcations of cervical caclage?

A

of membranes, bleeding, pregnancy loss (due to onset of labour, miscarriage process), bladder injury, anaesthetic risks (GA/spinal)

47
Q

how does progesterone reduce risk of PTL? How is it given (dosing?

A

Progesterone acts by inhibiting myometrial contractions & cervical ripening to reduce PTD and neonatal mortality & morbidity.

weekly IM progesterone or daily PV progesterone

48
Q

what are the indications for progesterone to reduce risk of PTL?

A

asymptomatic women with a singleton pregnancy & cervical length <25mm in the mid trimester or women with previous preterm birth

49
Q

what is the optimum timing to start progesterone?

A

started at 16 – 20 weeks until 36 weeks

50
Q

Antenatal screening and treatment of bacterial vaginosis, trichomoniasis, candidiasis before ______________ may be beneficial in reducing PTL:
• Using genital swabs & antibiotics

A

20 weeks gestation

Woman's Health (29 decks)

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