Lecture 16: Preterm labour Flashcards
Define preterm birth (ptb), very and extreme ptb and the % causes
Birth before 37 wks with Very Ptb <32 and Extreme Ptb <28 wks.
This can be spontaneous (80%)- abnormality/pathology of quiescence
or Indicated- on balance it is safer for the mother/baby- eg. fgr, pre-eclampsia
What are the 4 pathological processes that can lead to early/abnormal activation and stimulation of birth
- Endocrine activation of the fetal HPA axis - fetal/maternal stress
- Inflammation/ infection
- Decidual haemorrhage
- Uterine distension
All four interact together with final common pathway
What causes pre term activation of fetal HPA axis
- Fetal stress
eg. Uteroplacental vascular insufficiency leading to Pre eclampsia or FGR - Maternal psychological stress- eg. depression/anxiety can activate maternal HPA axis, leading to 2x more Ptb
What are the causes of inflammation and infection leading to ptb
Ascending infection can lead to ECM degradation involved in cervical ripening directly or indirectly by triggering inflammation ->leukocyte infiltration, COX making PGE2 which is uterotonic
These can be
- untreated STI- chylamydia, gonorrhoea
- Asymptomatic bacteriuria
- Low Lactobacillus in vaginal flora is associated with ptb
How does decidual haemorrhage lead to ptb
- Damage of decidual bv leads to retroplacental haematoma
- Thrombin is activated as part of the coagulation cascade which leads to
- increased myometrial contractions
- upregulate matrix metalloproteinase to lead to rupture of membranes
- inhibit expression of P2 receptors = functional withdrawal- starts labour
How does uterine distension cause ptb
If muscle cells are stretched eg. in polyhydaramnios, multiple pregnancy,
they have increased CAP and connexin 43 - part of activation stage of labour
What is cervical insufficiency and the risk factors for it
Dilation and/or effacement of cervix without contractions,
usually resulting in pre-viable loss (16-22)
Congenitally rare CT disorders- ehlers-danlos syndrome, more commonly due to cervical injury/distension with surgery
Cerclage is helpful
What are the short term (5) and long term (6) complications of prematurity for the neonate
Short
- Respiratory distress syndrome
- Apnea
- sepsis
- hypothermia
- hypoglycaemia
Long
- bronchopulmonary dysplasia
- retinopathy of prematurity
- patent ductus arteriosus ->pulmonary hypertension
- nectrotising enterocollitis - require resection of bowel
- Brain disorders: Interventricular haemorrhage
- Periventricular Leukomalacia
What makes some of the big psychosocial, financial impact on parents/ families of pre term baby
- Fetus unwell to be held, has to be kept ventilated, breast feeding not established
- Increased chance of maternal comorbidities, +/-complicated c section.
–> increased stay at hospital away from work, home,
What are some lifetime complications of prematurity
- Recurrent hospitalisations for resp- asthma, gi- gastroenteritis
- Neurodevelopmental disabilities = behavioural, psychological, motor deficit/delay
-Chronic health problems
= CKD, Hypertension, impaired lung function, insulin resistance, obesity, CVD
Define Viability, age for periviability and what factors influence to make worse outcomes (7)
Gestational age where a baby can be resuscitated at delivery and survive without significant morbidity
This is around 23-24 wks +6 days is (periviable) Worse outcomes influenced by
- less Gestational age
- immature Lung development
- FGR, infections
- Males sex
- preterm premature rupture of membranes
- born outside of 3’ hospital- staff, resources
How can viability be favourably increased
- Increase lung maturity (cod is RDS, BPD) by inducing surfactant production with antenatal corticosteroids (2 doses 24hrs apart imi- 1-7 days before delivery).
- AC also reduces fetal lung fluid and
- alters response to oxidative stress to reduce death, RDS, NEC and IVH
- Surfactant reduces surface tension in alveoli to reduce work of breathing
What are modifications to risk factors for PTB prior to pregnancy and in pregnancy to help reduce PTB
Prior to pregnancy
- decrease need for cervical surgery- HPV vaccine, contraception
- optimise interpreg interval
- optimise maternal health
In pregnancy ,
- stop smoking/substance abuse
- Screen and treat for STI, UTI
- Encourage prenatal care
- Decrease risk of pre-eclampsia
What is the FFN screening tests for increased risk of PTB
Fetal Fibronectin
- high mw glycoprotein in the choriodecidual space as a bio glue
- Do swab of cervico/vaginal fluids of asymptomatic women with high risk factors at 22-27+6 to show disruption of fusion of membranes with decidua
- needs to be combined with cervical length and history
In symptomatic abdo pain woman (- 24-34 wks) more helpful for chance of delivery in 7-10 days. neg is good for no tocolytics
What happens and when is the cervical length screening test for PTB
- only helpful in high risk women
Transvaginal screen of Cervical length measured at 16-24 wks.
A smaller cervical length indicates increased likelihood of less gestation at birth.
Best done in conjunction with high risk factors for PTB
