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Preterm birth Flashcards

1
Q

Incidence of PTB

A

5-10% of births
7% in NZ, 8% in Australia
Extreme PTB <28 weeks = 0.5% in NZ

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2
Q

Definition of extreme preterm, very preterm, and moderate-late preterm - gestations

A

extremely preterm = less than 28 weeks
- combined 2% of births in Australia

very preterm = 28 to 32 weeks
- combined 2% of births in Australia

Moderate to late preterm = 32 to 37 weeks
7% of births in Australia

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3
Q

Broad causes of PTB - rule of thirds

A

1/3 = iatrogenic e.g. PET, severe IUGR

1/3 = following PPROM

1/3 = spontaneous labour

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4
Q

Causes of preterm birth = PICFUPS

A

P = previous PTB (15% with 1x PTB, 30% with 2x, 45% with 3x)

I = infection
Intrauterine = ascending (BV, trich, chlamydia, gonorrhoea, GBS, gardnerella, mycoplasma, ureaplasma, kleibsiella, E coli), transplacental via maternal blood stream (bacteraemia), from abdomen via tubes (e.g. appendicitis, TOA), introduced via procedure (e.g. amniocentesis)
Extrauterine = sepsis e.g. urosepsis, pneumonia, viral, peridontal disease

C=cervix
Shortened cervix - previous LLETZ >1cm, cone biopsies, previous D+Cs/STOPs, cervical trauma in previous deliveries, CS at full dilatation

F=fetal
Chromosomal or congenital abnormalities

U=uterine (OUT)
Overdistension (polyhydramnios, LGA, multiple pregnancy), uterine structural abnormalities (bicornuate/septate), trauma

P=placenta
Placental abruption, placental insufficiency

S=social
Substance use (smoking, ETOH, drugs)
Low SES, Maori/Pacific/Indigenous
Low pre-pregnancy weight
AMA
Stress, IPV
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5
Q

History taking

A

PC - abdo pain, back pain, ROM, FM, localising sx of infection
Pregnancy this far
PTB risk factors
Gestation accurate?
Whether appropriate to do fFN = no bleeding, PPROM, VE, intercourse

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6
Q

NICE Guidance on USS Cx length vs fFN

A

Treat as TPTL if 29+6 or less based on clinical assessment only

If 30+0 or more
Offer TV ultrasound first line
If > 15mm - unlikely preterm labour, consider other diagnoses and offer inpatient observation vs outpatient
If 15mm or less - diagnose preterm labour

Offer FFN if TVUSS not available or acceptable
If 50ng/ml or less - unlikely preterm labour, consider other diagnoses and offer inpatient observation for outpatient
If >50ng/ml - diagnose preterm labour

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7
Q

Maternal and Fetal Impacts of PTB

A

Maternal
Increased operative birth
Increased PPH
Reduced bonding due to increased NICU admissions
Increased postpartum depression and anxiety
Morbidity related to underlying cause - infection, abruption, PET

Fetal
Intrapartum hypoxia
Low birth weight
Hypothermia
Hypoglycaemia
Respiratory - TTN, RDS, surfactant deficiency, BPD, apnoeas
Cardiac - PDA
Gut - NEC
Brain - IVH
Jaundice
Retinopathy
Neonatal death
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8
Q

Counselling in event of PTL or TPTL

A

Discuss implications for mother and baby, short and long term consequences

Consider gestation - active management vs palliative

If active: steroids, tocolysis unless contraindications, MgSO4, benzylpenicillin, NICU availability - transfer in-utero or ex-utero

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9
Q 
BV
Definition
Associated organisms
Does routine treatment of BV reduce PTB?
Who should we treat for BV?
A

Imbalance of vaginal flora - reduction in protective acids producing lactobacilli and overgrowth of BV associated organisms:
Gardnerella vaginalis,
bactericides, peptostreptococcus, mycoplasma species, atopbium species, moriluncun species

Routine treatment of BV in pregnancy is not associated with reduced PTB or PPROM

Treat those with other risk factors for preterm birth
Treat those who are symptomatic

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10
Q

MgSO4 for neuroprotection: dose and monitoring

A

Dose
4g bolus over 25-20 minutes
Then IV infusion 1g per hour until birth or for 24 hours (Which ever is sooner)

Monitoring
At least 4 hourly HR, BP, RR, deep tendon reflexes, UO

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11
Q

Rescue cerclage indications and contraindications

A

Indications

  • 16+0 - 27+6
  • Dilated cervix, exposed, unruptured membranes

Contraindications

  • Vaginal bleeding
  • Uterine contractions
  • Signs of infection
  • Ruptured membranes
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12
Q

Caesarean section - choice of uterine incision

A

Depends on presence of lower segment, position of fetus, multiple pregnancy, placental location, membranes ruptured

Options - classical, upper transverse, J or T

Classical facilitate atraumatic and rapid delivery of the fetus

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13
Q

Ventouse and forceps contraindicated before what gestation?

A

Ventouse contraindicated < 34 weeks
Forceps relatively contraindicated < 34 weeks - perform with caution, do not perform rotational forceps, only if certain of position

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14
Q

FSE and FBS contraindicated before what gestation?

A

34/40

Avoid FSE if <34+0/40 unless it is not possible to monitor externally
AND has been discussed with a senior obstetrician AND benefits outweigh risks
AND alternatives and inappropriate to the woman

FBS - avoid if less that 34+0/40

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15
Q

Cervical length measurements and risk of PTB <37 weeks

Length 30mm, 27mm, 22mm

A

30mm (10th centile) - RR 3.8
27mm (5th centile) - RR 5.4
22mm (2.5th centile) - RR 6.3
(Median length at 20 week is 42mm)

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16
Q

USS technique for cervical measurement

A

Consider TA scan with partially full bladder as potential firstline screening test. If >35mm do not need TV USS.

Most accurately measured using TV ultrasound

  • Empty bladder
  • Probe in anterior fornix, minimising pressure on cervix
  • Measure from internal to external os, take smallest of three measurements over 5 minutes (As cervix is dynamic)

Transperineal not adequately studied

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17
Q

Cervical USS assessment - Predictive value of funnelling and shortening with fundal pressure, or presence of amniotic sludge?

A

Associated with PTB but don’t contribute to predictive monitoring beyond the cervical length itself

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18
Q

Progesterone vs cerclage in LOW RISK WOMEN? RR?

A

Progesterone - RR 0.66 (ie reduces risk by 34%) reduces risk of preterm delivery before 34 weeks or fetal death. NNT = 11.

Progesterone also reduces risk of RDS, composite neonatal morbidity and mortality,
birthweight <1.5kg, admission to NICU

Cervical cerclage

  • RR 0.74 if low risk
  • RR 0.61 if previous PTB.

No clear benefit of cerclage to progesterone, therefore progesterone is generally preferred treatment as avoids surgical risks.

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19
Q

Role of progesterone vs cerclage in WOMEN WITH RFS FOR PRETERM BIRTH? RR?

A
  1. Previous PTB
    - benefit from progesterone or cerclage, consider cervical length surveillance to guide decision and if progressive shortening consider cerclage.
  2. Multiple pregnancy
    - Cervical length has predictive value however there
    is conflicting evidence regarding therapeutic intervention.
  3. Previous cervical excisional procedure - can help stratify risk for women and determine appropriateness of intervention
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20
Q

Possible interventions for shortened cervix or women with multiple RFs

A
  1. Conservative:
    - If no risk factors or patient declines
    - Consider cervical length monitoring
  2. Progesterone
    - CONSIDER if history of PTB <34 weeks but normal cervical length
    - RECOMMEND if CL <25mm (singleton or multi)
  3. Cervical cerclage
    - CONSIDER if history of PTB, PPROM or cervical surgery AND cervix <25mm
  • No significant difference between two interventions and increased risk with cerclage
  • Therefore, progesterone should be firstline in these women with serial cervical length in 1-2 weeks
  • If further shortening of cervix despite progesterone, consider cerclage
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21
Q

PV progesterone mechanism of action?

A

Reduces myometrial sensitivity to oxytocin
Blocks adrenergic receptors and prostaglandin synthesis
Stimulates lymphocyte associated synthesis of progesterone induced blocking
factor

Progesterone insufficiency thought to trigger uterine contractility

22
Q

Second and third trimester timing of progesterone

A

From 16-24 weeks, until 34-36 weeks

23
Q

Progesterone benefits, and safety profile

A

Reduced risk of PTB in meta-analysis - RR 0.66. NNT 11.

Also reduced risk of RDS, composite neonatal morbidity and mortality, birthweight <1.5kg, admission to NICU

No evidence of teratogenicity or adverse childhood outcomes (2 year follow up - OPPTIMUM trial)

24
Q

Cerclage timing

A

From 12-14 weeks for history indicated (2 or more early PTB)

From 16-24 weeks for ultrasound indicated

25
Q

Risks of cercvical cerclage

A

ROM, chorioamnionitis, bleeding, cervical trauma, anaesthetic risks

Average additional gestational time added - prolongs pregnancy for average of 6 weeks. Could still end up with a pre-viable or very preterm baby

26
Q

Types of cervical cerclage

A

Transvaginal

  • Shirodkar (buried, needs spinal to remove)
  • McDonald

Transabdominal

  • When vaginal sutures have failed
  • Bladder is reflected and suture placed over the internal os
  • Stays in place, delivery via CS
27
Q

Contraindications to cerclage

A

Rupture of membranes
APH
Evidence of infection
Uterine activity

28
Q

Gestation range for insertion of rescue cerclage

A

16-28 weeks with a dilated cervix and exposed membranes - discuss with SMO and paeds

29
Q

Rescue cerclage insertion process

A 
Trendelenburg
Consider uterine relaxant
Reduce prolapsed membranes with smooth surfaced device such
as inflated IDC balloon
Use McDonalds suture
Remain in hospital for 1 night
Follow up 2 weeks post insertion
30
Q

Contraindications to MgSO4

A

myasthenia gravis
myocardial compromise/ conduction defects (anti-inotropic effects)
Caution with impaired kidney function - use 0.5g/hr

31
Q

MgSO4 for neuroprotection in PTB - mechanisms of action

A

Exact mechanism not fully understood. Likely combination of following

Down regulation of excitatory stimuli

  • blocks NMDA receptors, preventing influx of calcium causing neuronal cell death
  • blocking NMDA receptors also decreases seizure threshold

Cerebral vasodilation through ca antagonism

  • leading to an increase in cerebral blood flow
  • minimising hypoxic ischaemic changes

Reduction of pro-inflammatory cytokines
Anti-apoptotic effect

32
Q

Steroids and Cochrane review 2017 - what are the benefits to infants? What do steroids not have an impact on?

A

Reduced rates of:

  • Neonatal Death RR 0.72
  • Respiratory Distress RR 0.66
  • Need for mechanical ventilation RR 0.68
  • Intraventricular Haemorrhage RR 0.55
  • Necrotising Enterocolitis RR 0.50
  • Systemic infection in the first 48 hours of life RR 0.6
No effect on:
Chronic lung disease
Mean birthweight
Death in childhood or adulthood
Neurodevelopment
Chorioamnionitis/endometritis
33
Q

Steroids optimal treatment to delivery interval

A

> 24 hours <7 days

No confirmed benefit in infants delivered >7 days after dose (possible some small benefit up to 14 days)

Still some benefit in those delivered less than 24 hours after the first dose

34
Q

Adverse effects of single course (1x pair) of steroids?

A

No known short term maternal or fetal adverse effects after single course

No known longer term risks of a single course in terms of cognitive/neurological effects

Insufficient evidence regarding multiple doses

35
Q

Contraindications to steroids

A

Requirement for acute delivery - do not delay delivery for purpose of steroid effect

Contraindication in systematic infection - TB, sepsis

Consider in chorioamnionitis but do not delay delivery for purpose of steroid effect

36
Q

Steroids and elective CS?
RCOG and Aus/NZ recommendations?
ASTECs study

A

RCOG suggest giving for elective CS up until 38+6

Aust/NZ Practice guideline suggest >34+6 if confirmed fetal lung immaturity

ASTECS study - reduced admission to SCBU with RDS (RR 0.46) but very low baseline risk at advancing gestation and no BSL measurements and long term outcomes

37
Q

Indication and gestation for rescue steroids (after initial pair)

A

Give if at ongoing risk of preterm delivery >7 days after single course

Give up to 3 x further rescue doses 1 week apart up til 32+6 (Aus/NZ Practice Guideline)

38
Q

ACTORDS study - repeat steroid doses - outcomes RR

A

Reduces RDS RR 0.82
reduces severe lung disease RR 0.6
reduces O2 use, mechanical ventilation, surfactant use.

Decreased birthweight, head circumference and length at birth but not at discharge.

Increased CS rate

No difference in rate of NICU admission, APGAR scores, NEC, Retinopathy of prematurity, IVH

2 year follow showed increase need for attention problems assessment but no difference in major neurosensory disability

39
Q

Rescue steroids Cochrane 2015 study results

A

Associated with reduced RDS (RR 0.83)

Associated with reduced serious infant outcome (RR 0.84)

Associated with reduced mean birthweight -76g (no difference when adjusted for birthweight)

No significant harm or benefit at 2 and 3 years (although ACTORDS found increased risk of need for assessment for attention problems)

40
Q

What is fFN?

When is it normally present in the cervicovaginal secretions?

A

Extracellular matrix glycoprotein present at the decidual-chorionic
interface

<16 weeks (prior to fusion of
chorion and amnion) and >37 week

41
Q

Why do we use the fFN test?

A

To help predict likelihood of preterm labour and guide use of steroids and tocolytics

42
Q

fFN cause of false positives?

Negative predictive value?

A

False positives: semen, blood, digital cervical examination, lubricant

99.7%

43
Q

fFN positive predictive values?

10, 50, 200, 500 ng/ml?

A 
Positive predictive value increases the higher the number
10ng/ml = 11-19% PPV
50ng/ml = 20-32% PPV
200ng/ml = 37- 61% PPV
500ng/ml = 46-75% PPV
44
Q

fFN sensitivity, specificity, positive and negative predictive values

A

Sensitivity 65%, PPV 43%

Specificity 93%, NPV 97%

45
Q

QUIPP tool for PTB

A

Use in two clinical settings:

  1. Asymptomatic women at high risk for PTB in preterm surveillance clinics (based on 1803 women)
  2. Symptomatic women e.g. abdominal pain, contractions, tightenings (based on 1032 women)

Relies on:
A clinical history for current risk factors and symptoms
FFN OR TV USS cervical length measurements (both is better, don’t need both)

1. Symptomatic
Symptom present Y/N
Previous cervical surgery Y/N
Previous preterm Y/N
Previous PPROM Y/N
Number of fetuses
Gestation of test
Shortest cervical length AND/OR
fFN result
2. Asymptomatic
Previous cervical surgery Y/N
Previous preterm Y/N
Previous PPROM Y/N
Previous late miscarriage 16-24/40 Y/N
Number of fetuses
Gestation of test
Shortest cervical length
fFN result
Gives results as percentage:
Within 1 week
Within 2 weeks
Within 4 weeks
Before 30/40
Before 34/40
Before 37/40
46
Q

PPROM incidence and risk factors

A

2-3% of pregnancies
PPROM precedes 1/3 of preterm births

RFs:
Previous PPROM
Infection - vaginal, urine, systemic infection
Uterine overdistension: multiple pregnancy, LGA, polyhydramnios
Uterine trauma
Short interpregnancy interval
Smoking/substance use

47
Q

Amnisure or Actim PROM tests to diagnose PPROM

A

Amnisure

  • Measures alpha micro globulin
  • Not affected by semen of small amounts of blood
  • Specificity = 87-100%
  • Sensitivity around 94-98%
  • Can be positive in up to 1/3rd of term woman with intact membranes in labour

Actim PROM test
- Measures insulin-like growth factor binding protein
(secreted by decidual and placental cells in high concentrations in amniotic fluid)
- Not affected by infection, urine, semen or small amounts of blood
- Specificity 98%
- Sensitivity 93%

48
Q

Likelihood of labouring after PPROM

  • Median time to delivery in general
  • Median time to deliviery for 24-28 weeks; 31 weeks
A

Medium time to delivery is 7 days (80% deliver within 7 days)

10 days at 24 -28 weeks

5 days at 31 weeks

25% deliver within 48 hour

49
Q

Risks of PPROM - fetal

A

Preterm labour, complications of prematurity (hypoxia, NEC, IVH, respiratory, low birthweight)

Chorioamnionitis

Ongoing pregnancy with PPROM: fetal lung hypoplasia, limb contractures, growth restriction

50
Q

Likelihood of lung hypoplasia if PPROM at 21 weeks, vs 29 weeks

A

If PPROM at 21 weeks - 90% have lung hypoplasia

If PPROM at 29 weeks - 10% have lung hypoplasia

51
Q

ORACLE 1 trial for PPROM

Abx used?
Findings

A

PPROM < 37/40, randomised to erythromycin, co-amoxiclav, both or neither.

Associated with prolongation of pregnancy, reduced surfactant use, reduced oxygen use at 28 days, reduced abnormal cerebral ultrasound

Increased NEC with augmentin (RR 4)

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