[59] Preterm Delivery Flashcards
What % of deliveries in developed countries are preterm?
Up to 12%
What are the causes of preterm delivery?
- Idiopathic
- Intrauterine stretch
- Intrauterine bleeding
- Cervical weakness
- Maternal medical conditions
- Fetal problems
- Intrauterine infection
What might cause intrauterine stretch leading to preterm delivery?
- Multiple gestation
- Polyhydramnois
- Uterine abnormality
What might cause intrauterine bleeding leading to preterm delivery?
- Abruption
- Antepartum haemorrhage
What maternal medical conditions might lead to pre-term delivery?
- Pre-eclampsia
- Chronic medical conditions
- Urinary tract infection
What fetal problems might lead to preterm delivery?
- IUGR
- Congenital malformations
What intrauterine infections may lead to preterm delivery?
- Chorioamnionitis
- Bacterial vaginosis
- Preterm prolonged rupture of membranes
What are the risk factors for preterm delivery associated with?
Generally predispose the mother to infection or inflammation
What are the risk factors for preterm delivery?
- Previous pre-term delivery
- Short interpregnancy interval of <6 months
- Maternal age
- Maternal nutrition
- Ethnicity
- Multiple births
- High levels of maternal psychological or social stress
- Smoking
- Substance misuse
- Maternal health
- Socio-economic deprivation
By how much does a previous preterm delivery increase the risk of another?
Twofold increased risk, increasing for each additional delivery
By how much does having a short inter-pregnancy interval of <6 months increase the risk of pre-term delivery?
More than doubles risk
What impact does maternal age have on pre-term delivery?
Increased risk of <20 or >35 years old
What effect does maternal nutrition have on the risk of pre-term delivery?
Low BMI increases the risk of spontaneous preterm birth.
Obese mothers are more likely to have preterm births for other indications, particularly pre-eclampsia and diabetes mellitus
How does ethnicity affect the risk of pre-term births?
Higher in black mothers
What % of cases of preterm delivery are associated with multiple births?
15-20%
When is delivery recommended for monochorionic twins?
By 37 weeks
Give an example of when maternal health might increase the risk of pre-term delivery
Infections, either localised, e.g. ascending, or generalised, e.g. malaria
What are the strategies that can be used to prevent pre-term labour?
- Progesterone
- Cervical cerclage
- Genital infection treatment
- Cessation of maternal smoking
- Reduction in multiple births by limiting embryo transfer in IVF treatment
- Reduction in elective preterm deliveries
What is the role of progesterone in the prevention of pre-term labour?
It is given prophylactically at 24 weeks to those at high risk of pre-term labour
What is the purpose of prophylactic progesterone in high-risk patients?
Reduces pre-term birth and perinatal morbidity in high risk patients
Give two examples of when progesterone prophylaxis might be given
- Previous preterm birth
- Short cervix identified on ultrasound
Is progesterone prophylaxis given when there are multiple fetuses?
No
What is cervical cerclage?
Purse-string sutures to maintain closure of the maternal cervix
When might cervical cerclage be used?
- Multiple pre-term brths
- Mid-trimester fetal loss
- Cervix is shortening
What alternative to cervical cerclage is being investigated?
Non-surgical ‘cervical pessary’
How useful are interventions to prevent preterm birth?
The potential impact of these interventions to reduce the proportion of infants born preterm is relatively small
What may be involved in the management of preterm delivery?
- Antenatal corticosteroids
- Tocolysis
- Magnesium sulfate
What is the main purpose of administering maternal corticosteroids before preterm birth?
Reduce the incidence of;
- Respiratory distress syndrome
- Intraventricular haemorrhage
- Neonatal death
By how much does the administration of maternal corticosteroids reduce the incidence of RDS?
44%
By how much does the administration of maternal corticosteroids reduce the incidence of intraventricular haemorrhage?
46%
By how much does the administration of maternal corticosteroids reduce the incidence of neonatal death?
31%
What other things is the administration of maternal corticosteroids associated with the reduction of?
- Necrotising enterocolitis
- Need for respiratory support
- Intensive care admission
- Systemic infections in first 48 hours of life
Who is offered maternal corticosteroids?
- Mothers at risk of preterm birth up to 35 weeks gestation
- Women having an elective ceserean section prior to 39 weeks gestation
Why are maternal corticosteroids offered to mothers having an elective c-section prior to 39 weeks gestation?
To reduce the risk of respiratory morbidity
Describe the course of maternal corticosteroids given
Single course
What does tocolysis do?
Suppress uterine contractions
What is the purpose of tocolysis?
Widely used to suppress contractions to enable completion of a course of antenatal corticosteroids, or allow maternal transfer to perinatal centre
When is magnesium sulfate offered?
When preterm delivery at 24-32 weeks is anticipated
What is the purpose of magnesium sulfate in preterm delivery?
Reduce the risk of cerebral palsy
How effective is magnesium sulfate in preventing cerebral palsy?
Several trials have shown a 30-40% reduction in cerebral palsy rates
What % of pregnancies are affected by preterm premature rupture of membranes (PPROM)?
2-3%
What % of pre-term deliveries are associated with PPROM?
25-30%
Why does PPROM increase neonatal morbidity and mortality?
Due to prematurity, infection, and pulmonary hypoplasia
What is a potential cause of PPROM?
Ascending maternal infection from the lower genital tract
What supports the link between PPROM and ascending maternal infection from lower genital tract?
About 1/3 have positive amniotic fluid cultures
What is involved in the management of PPROM?
- Antibiotics
- Delivery
- Corticosteroids
What is the role of antibiotics in PPROM?
Reduce chorioamnionitis and neonatal infection
What does the decision to deliver or manage expectantly require in PPROM?
Balancing the risk of intrauterine infection compared with neonatal risks from prematurity
What should be done if delivery before or at 34 weeks is required in PPROM?
Corticosteroids are given
When is delivery usually indicated in PPROM?
Beyond 34 weeks
What is the overall aim in preterm delivery?
Prolong pregnancy for as long as possible while ensuring the safety of the mother and fetus
What is considered to be extreme preterm delivery?
<28 weeks
What is the limit of viability?
22-26 weeks
Who should the decision about timing of a preterm delivery at the limit of viability involve?
- Obstetrician
- Neonatologist
- Parents
What is decision making aided by when deciding timing of pre-term delivery at the limit of viability?
Detailed assessment of fetal wellbeing
What is involved in a detailed assessment of fetal wellbeing?
- Amniotic fluid volume
- Fetal heart rate monitoring
- Doppler studies
- Fetal growth
- Gestation
- Predicted birthweight
What epidemiological evidence can help inform decisions about delivery at the limit of viability?
Knowledge of outcomes at these early gestational ages, with national and international data
Where should delivery of extremely pre-term babies take place?
At a perinatal center
Why should the delivery of an extremely preterm baby take place at a perinatal centre?
To avoid subsequent transfer and separation of the infant and mother
How does the health of infants born at 34-38 weeks compare to term infants?
They have an increase in respiratory morbidity and mortality, and increased length of stay in hospital compared to term infants. There are also higher neurodisability rates
