Repeated Doses of Antenatal Corticosteroids for Women at Risk of Preterm BirthAhmed Alaa el dinAssistant Lecturer of OB/GYNCairo University

IntroductionPreterm birth is a leading cause of perinatal death and disability and is an important public health problem globally.

Administration of corticosteroids to mothers before preterm delivery significantly reduces perinatal morbidity and mortality.

Complications of preterm birth include:-Respiratory distress.-Intraventricular hemorrhage.-Periventricular leukomalacia.-Necrotizing enterocolitis.-Need for mechanical ventilation & admission to NICU.-Perinatal death.

Mechanism of Action of Antenatal Corticosteroids

A. Respiratory ActionAntenatal corticosteroid therapy leads to architectural and biochemical changes that improve both lung mechanics and gas exchange. These changes are primarily the result of accelerated morphologic development of type 1 and type 2 pneumocytes. Type 1 pneumocytes are responsible for gas exchange in the alveoli, while type 2 pneumocytes are responsible for production and secretion of surfactant.

Antenatal corticosteroids also alter production of surfactant binding proteins and enhance fetal lung antioxidant enzymes.

However, for these changes to occur the lungs need to have reached a stage of development that is biologically responsive to corticosteroids.

B. Circulatory ActionAntenatal corticosteroid therapy improves circulatory stability in preterm neonates, resulting in less intraventricular hemorrhage and necrotizing enterocolitis.

Rationale for Repeating antenatal corticosteroids

Rationale for Repeating antenatal corticosteroidsThe biologic rationale for repeating antenatal corticosteroid therapy is based upon the observation that biochemical stimulation of surfactant production appears to be reversible in cell culture models i.e. surfactant protein mRNA levels decline to control levels after cortisol is removed.

However, other beneficial effects, such as cytostructural maturation, persist after steroid exposure is withdrawn.

Effective Antenatal Corticosteroid Regimens

Corticosteroid RegimensCorticosteroid regimens shown to be effective include: betamethasone 12 mg intramuscularly, 2 doses 24 hours apart; or dexamethasone 6 mg intramuscularly 4 doses 12 hourly.

Benefits were found when treatment was started between 26 and 35 weeks of gestation, and for babies born 17 days after commencing treatment.

No benefits were demonstrated for treatment commenced, or infants born, before 26 weeks of gestation, nor for those born more than seven days after treatment.

Corticosteroid RegimensSome studies showed that betamethasone is associated with lower incidence of RDS compared to dexamethasone.

Dexamethasone is associated with lower incidence of intraventricular hemorrhage, but with higher incidence of puerperal sepsis (especially if taken orally).

Advantages & Disadvantages of Repeated Antenatal Corticosteroids

AdvantagesRepeated doses are associated with better neonatal lung function than single course of corticosteroids, particularly among infants delivered before 32 weeks of gestation.

Also, less need for mechanical ventilation, continuous positive airway pressure, and surfactant use. There was also a reduction in the frequency of pneumothorax.

However, there is NO SIGNIFICANT BENEFIT in reduction of severe respiratory distress syndrome, grade III or IV intraventricular hemorrhage, chronic lung disease or periventricular leukomalacia.

DisadvantagesRepeated doses are associated with lower birth weight than the single course, and appear to cause IUGR.

However, it was found that repeating a SINGLE RESCUE DOSE or COURSE, does not affect fetal growth.

Some studies reported increased incidence of cerebral palsy.

Regarding late term effects, some studies showed affection of neurological development in early childhood.

DisadvantagesIn animals: studies have shown decreased brain size, altered nerve growth, a delayed rate of myelination, altered retinal development, a decrease in the number of neurons and a dose-dependent degeneration of neurons in the hippocampus. Also it may be associated with increased incidence of hypertension.

Recommendations

RecommendationsWe recommend repeating a SINGLE RESCUE DOSE or COURSE of antenatal corticosteroids only in cases who have passed 7 days since initial administration & are still at risk of preterm labor.

Thank

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