Retinal maturation is delayed by repeated, but not single, maternal injections of betamethasone in sheep

Tracing the influence of prenatal risk factors on the offspring retina: Focus on development and putative long-term consequences

BACKGROUND

Pregnancy represents a window of vulnerability to fetal development. Disruptions in the prenatal environment during this crucial period can increase the risk of the offspring developing diseases over the course of their lifetime. The central nervous system (CNS) has been shown to be particularly susceptible to changes during crucial developmental windows. To date, research focused on disruptions in the development of the CNS has predominantly centred on the brain, revealing a correlation between exposure to prenatal risk factors and the onset of neuropsychiatric disorders. Nevertheless, some studies indicate that the retina, which is part of the CNS, is also vulnerable to in utero alterations during pregnancy. Such changes may affect neuronal, glial and vascular components of the retina, compromising retinal structure and function and possibly impairing visual function.

METHODS

A search in the PubMed database was performed, and any literature concerning prenatal risk factors (drugs, diabetes, unbalanced diet, infection, glucocorticoids) affecting the offspring retina were included.

RESULTS

This review collects evidence on the cellular, structural and functional changes occurring in the retina triggered by maternal risk factors during pregnancy. We highlight the adverse impact on retinal development and its long-lasting effects, providing a critical analysis of the current knowledge while underlining areas for future research.

CONCLUSIONS

Appropriate recognition of the prenatal risk factors that negatively impact the developing retina may provide critical clues for the design of preventive strategies and for early therapeutic intervention that could change retinal pathology in the progeny.

Impact of postnatal steroids on peripheral avascular retina and severity of retinopathy of prematurity

BACKGROUND

We investigated the role of postnatal steroids on the severity of retinopathy of prematurity (ROP) and its impact on peripheral avascular retina (PAR).

METHODS

A retrospective cohort study of infants born at ≤32 weeks gestation and/or birth weight ≤1500 g. Demographics, the dose and duration of steroid treatment, and age when full retinal vascularization occurred were collected. The primary outcomes were the severity of ROP and time to full vascularization of the retina.

RESULTS

A total of 1695 patients were enrolled, 67% of whom received steroid therapy. Their birth weight was 1142 ± 396 g and gestational age was 28.6 ± 2.7 weeks. The total hydrocortisone-equivalent dose prescribed was 28.5 ± 74.3 mg/kg. The total days of steroid treatment were 8.9 ± 35.1 days. After correction for major demographic differences, infants who received a higher cumulative dose of steroids for a longer duration had a significantly increased incidence of severe ROP and PAR (P < 0.001). For each day of steroid treatment, there was a 3.2% increase in the hazard of the severe form of ROP (95% CI: 1.022-1.043) along with 5.7% delay in achieving full retinal vascularization (95% CI: 1.04-1.08) (P < 0.001).

CONCLUSION

Cumulative dose and duration of postnatal steroid use were independently associated with the severity of ROP and PAR. Thus, postnatal steroids should be used very prudently.

IMPACT

We report ROP outcomes in a large cohort of infants from two major healthcare systems where we have studied the impact of postnatal steroids on the severity of ROP, growth, and development of retinal vessels. After correcting our data for three major outcome measures, we show that high-dose postnatal steroids used for a prolonged duration of time are independently associated with severe ROP and delay in retinal vascularization. Postnatal steroids impact the visual outcomes of VLBW infants significantly, so their clinical use needs to be moderated.

The role of antenatal corticosteroids in twin pregnancy

Twin pregnancy was associated with significantly higher rates of adverse neonatal and perinatal outcomes. One of the underlying causes is that twins are prone to preterm birth. Antenatal corticosteroids are widely used for reducing the incidence of neonatal respiratory distress syndrome initially and other neonatal mortality and morbidities subsequently. As it is widely used as a prophylactic treatment for potential premature births, there remain controversies of issues relating to twin gestations, including window for opportunity, timing of use, repeat course, optimal administration-to-delivery intervals, dosage, and type of corticosteroid. Thus, we present a thorough review of antenatal corticosteroids usage in twin gestation, emphasizing the aforementioned issues and attempting to offer direction for future investigation and clinical practice.

Antenatal corticosteroids and neurodevelopmental outcomes in late preterm births

OBJECTIVES

Antenatal corticosteroids (ACS) decrease neonatal mortality and morbidity among preterm neonates, yet there has been concern regarding their long-term safety. We hypothesised that potential long-term adverse effects of ACS may be observed among infants born during the late preterm period (LPT, 34^0/7-36^6/7 weeks of gestation), when the benefits of ACS are subtle.

DESIGN

Population-based, retrospective cohort.

SETTING

Ontario, Canada, between 2006 and 2011.

PATIENTS

All live singleton infants born during the LPT period with a minimum 5-year follow-up.

INTERVENTIONS

Exposure to ACS prior to 34^0/7 weeks of gestation.

MAIN OUTCOME MEASURES

Suspected neurocognitive disorder, audiometry testing or visual testing.

RESULTS

Overall, 25 668 infants were eligible for analysis, of whom 2689 (10.5%) received ACS. Infants in the ACS group had lower mean birth weight and higher rates of birth weight <10th percentile, neonatal resuscitation and neonatal intensive care unit admission. At 5 years of age, ACS exposure was associated with an increased risk of suspected neurocognitive disorder (adjusted HR (aHR) 1.12, 95% CI 1.05 to 1.20), audiometry testing (aHR 1.20, 95% CI 1.10 to 1.31) and visual testing (aHR 1.06, 95% CI 1.01 to 1.11).

CONCLUSION

In children born during the LPT period, exposure to ACS prior to 34^0/7 weeks of gestation is associated with an increased utilisation of the healthcare system related to audiometry and visual testing and suspected neurocognitive disorders by 5 years of age.

A Growing Dilemma: Antenatal Corticosteroids and Long-Term Consequences

OBJECTIVE

A single course of synthetic antenatal corticosteroids is standard care for women considered to be at risk for preterm birth before 34 weeks of gestation. While the intended target is the fetal lung, the fetal brain contains remarkably high levels of glucocorticoid receptors in structures critical in the regulation of behavior and endocrine function. Negative programming signals may occur which can lead to permanent maladaptive changes and predispose the infant/child to an increased risk in physical, mental, and developmental disorders.

METHODS

Framed around these areas of concerns for physical, mental, and developmental disorders, this narrative review drew on studies (animal and clinical), evaluating the long-term effects of antenatal corticosteroids to present the case that a more targeted approach to the use of antenatal corticosteroids for the betterment of the fetus urgently needed.

RESULTS

Studies raised concerns about the potential negative long-term consequences, especially for the exposed fetus who was born beyond the period of the greatest benefit from antenatal corticosteroids. The long-term consequences are more subtle in nature and usually manifest later in life, often beyond the scope of most clinical trials.

CONCLUSION

Continued research is needed to identify sufficient safety data, both short term and long term. Caution in the use of antenatal corticosteroids should be exercised while additional work is undertaken to optimize dosing strategies and better identify women at risk of preterm birth prior to administration of antenatal corticosteroids.

KEY POINTS

· A single-course ACS is a remarkable therapy with substantial benefits.. · There is a potential of long-term neurodevelopmental consequences in the ACS-exposed fetus.. · There is a need to improve dosing strategies and identification of appropriate at risk women..

Neurodevelopmental disorders among term infants exposed to antenatal corticosteroids during pregnancy: a population-based study

OBJECTIVE

An increasing proportion of fetuses are exposed to antenatal corticosteroids (ACS). Despite their immediate beneficial effects, the long-term safety of ACS has been an ongoing source of concern. In the current study, we assessed the likelihood of neurodevelopmental problems among term infants exposed to ACS earlier in pregnancy compared with non-exposed term infants.

DESIGN

Retrospective cohort study (2006-2011). Median duration of follow-up was 7.8 (IQR 6.4-9.2) years.

SETTING

Population-based study, Ontario, Canada.

PARTICIPANTS

All live singleton infants born at term (≥37^0/7 weeks gestation) (n=529 205).

EXPOSURE

ACS during pregnancy.

PRIMARY AND SECONDARY OUTCOME MEASURES

A composite of diagnostic or billing codes reflecting proven or suspected neurodevelopmental problems during childhood including audiometry testing, visual testing or physician service claim with a diagnosis code related to a suspected neurocognitive disorder.

RESULTS

At 5 years of age, the cumulative rate for the primary outcome was higher among infants exposed to ACS compared with non-exposed infants: 61.7% (3346/5423) vs 57.8% (302 520/523 782), respectively (p<0.001; number needed to harm (NNH)=25, 95% CI 19 to 38; adjusted HR (aHR) 1.12, 95% CI 1.08 to 1.16). Similar findings were observed for each of the individual components of the primary outcome: 15.3% vs 12.7% for audiometry testing (p<0.001; NNH=39, 95% CI 29 to 63; aHR 1.18, 95% CI 1.11 to 1.25); 45.4% vs 43.5% for visual testing (p=0.006; NNH=54, 95% CI 31 to 200; aHR 1.08, 95% CI 1.04 to 1.12) and 25.8% vs 21.6% for suspected neurocognitive disorder (p<0.001; NNH=24, 95% CI 19 to 33; aHR 1.16, 95% CI 1.10 to 1.21).

CONCLUSIONS

We found an association among term infants between exposure to ACS during pregnancy and healthcare utilisation during childhood related to suspected neurocognitive and neurosensory disorders.

Antenatal Corticosteroid Exposure Disrupts Myelination in the Auditory Nerve of Preterm Sheep

BACKGROUND

Antenatal corticosteroids (ACS) improve preterm neonatal outcomes. However, uncertainty remains regarding the safety of ACS exposure for the developing fetus, particularly its neurosensory development.

OBJECTIVES

We investigated the effect of single and multiple ACS exposures on auditory nerve development in an ovine model of pregnancy.

METHODS

Ewes with a single fetus (gestational age [GA] 100 days) received an intramuscular injection of 150 mg medroxyprogesterone-acetate, followed by intramuscular (i) betamethasone (0.5 mg/kg) on days 104, 111, and 118 GA; (ii) betamethasone on day 104 and saline on days 111 and 118 GA; or (iii) saline on days 104, 111, and 118 GA, with delivery on day 125 GA. Transmission electron microscope images of lamb auditory nerve preparations were digitally analyzed to determine auditory nerve morphology and myelination.

RESULTS

Relative to the control, mean auditory nerve myelin area was significantly increased in the multiple-treatment group (p < 0.001), but not in the single-treatment group. Increased myelin thickness was significantly changed only in a subgroup analysis for those axons with myelin thickness greater than the median value (p < 0.001). Morphological assessments showed that the increased myelin area was due to an increased likelihood of decompacted areas (p = 0.005; OR = 2.14, 95% CI 1.26-3.63; 31.6 vs. 18.2% in controls) and irregular myelin deposition (p = 0.001; OR = 5.91, 95% CI 2.16-16.19; 49.0 vs. 16.8% in controls) in the myelin sheath.

CONCLUSIONS

In preterm sheep, ACS exposure increased auditory nerve myelin area, potentially due to disruption of normal myelin deposition.

Development of somatosensory-evoked potentials in foetal sheep: effects of betamethasone

AIM

Antenatal glucocorticoids are used to accelerate foetal lung maturation in babies threatened with premature labour. We examined the influence of glucocorticoids on functional and structural maturation of the central somatosensory pathway in foetal sheep. Somatosensory-evoked potentials (SEP) reflect processing of somatosensory stimuli. SEP latencies are determined by afferent stimuli transmission while SEP amplitudes reveal cerebral processing.

METHODS

After chronic instrumentation of foetal sheep, mothers received saline (n = 9) or three courses of betamethasone (human equivalent dose of 2 × 110 μg kg^-1 betamethasone i.m. 24 h apart, n = 12) at 0.7, 0.75 and 0.8 of gestational age. Trigeminal SEP were evoked prior to, 4 and 24 h after each injection and at 0.8 of gestational age before brains were histologically processed.

RESULTS

Somatosensory-evoked potentials were already detectable at 0.7 of gestation age. The early and late responses N20 and N200 were the only reproducible peaks over the entire study period. With advancing gestational age, SEP latencies decreased but amplitudes remained unchanged. Acutely, betamethasone did not affect SEP latencies and amplitudes 4 and 24 h following administration. Chronically, betamethasone delayed developmental decrease in the N200 but not N20 latency by 2 weeks without affecting amplitudes. In parallel, betamethasone decreased subcortical white matter myelination but did not affect network formation and synaptic density in the somatosensory cortex.

CONCLUSION

Somatosensory stimuli are already processed by the foetal cerebral cortex at the beginning of the third trimester. Subsequent developmental decrease in SEP latencies suggests ongoing maturation of afferent sensory transmission. Antenatal glucocorticoids affect structural and functional development of the somatosensory system with specific effects at subcortical level.

Association between gestational age at birth, antenatal corticosteroids, and outcomes at 5 years: multiple courses of antenatal corticosteroids for preterm birth study at 5 years of age (MACS-5)

Background

The Multiple Courses of Antenatal Corticosteroids for Preterm Birth Study (MACS) showed no benefit in the reduction of major neonatal mortality/morbidity or neurodevelopment at 2 and 5 years of age. Using the data from the randomized controlled trial and its follow-up, the aim of this study was to evaluate the association between gestational ages at birth in children exposed to single versus multiple courses of antenatal corticosteroid (ACS) therapy in utero and outcomes at 5 years of age.

Method

A total of 1719 children, with the breakdown into groupings of <30, 30–36, and ≥ 37 weeks gestation at birth, contributed to the primary outcome: death or survival with a disability in one of the following domains: neuromotor, neurosensory, and neurobehavioral/emotional disability and were included in this analysis.

Results

Gestational age at birth was strongly associated with the primary outcome, p < 0.001. Overall, the interaction between ACS groups and gestational age at birth was not significant, p = 0.064. Specifically, in the 2 preterm categories, there was no difference in the primary outcome between single vs. multiple ACS therapy. However, for infants born ≥37 weeks gestation, there was a statistically significant increase in the risk of the primary outcome in multiple ACS therapy, 48/213 (22.5%) compared to 38/249 (15.3%) in the single ACS therapy; OR = 1.69 [95% CI: 1.04, 2.77]; p = 0.037.

Conclusion

Preterm birth (<37 weeks gestation) remained the primary factor contributing to an adverse outcome regardless of the number of courses of ACS therapy. Children born ≥ 37 weeks and exposed to multiple ACS therapy may have an increased risk of neurodevelopmental/neurosensory impairment by 5 years of age. To optimize outcomes for infants/children, efforts in reducing the incidence of preterm birth should remain the primary focus in perinatal research.

Trial registration

This study has been registered at (identifier NCT00187382)

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2393-14-272) contains supplementary material, which is available to authorized users.

Glucocorticoids and fetal programming part 1: Outcomes

Fetal development is a critical period for shaping the lifelong health of an individual. However, the fetus is susceptible to internal and external stimuli that can lead to adverse long-term health consequences. Glucocorticoids are an important developmental switch, driving changes in gene regulation that are necessary for normal growth and maturation. The fetal hypothalamic-pituitary-adrenal (HPA) axis is particularly susceptible to long-term programming by glucocorticoids; these effects can persist throughout the life of an organism. Dysfunction of the HPA axis as a result of fetal programming has been associated with impaired brain growth, altered behaviour and increased susceptibility to chronic disease (such as metabolic and cardiovascular disease). Moreover, the effects of glucocorticoid-mediated programming are evident in subsequent generations, and transmission of these changes can occur through both maternal and paternal lineages.

Pregnancy-associated retinal diseases and their management

Pregnancy-associated retinal diseases are conditions that may occur uniquely in pregnancy or, more commonly, general conditions that may worsen or alter during pregnancy as a result of hematologic, hormonal, metabolic, cardiovascular, and immunologic changes. Diabetic retinopathy (DR) is by far the most common retinal condition that is altered by pregnancy. However, there are currently no widely accepted, precise clinical guidelines regarding its management during pregnancy. At present it is not possible to predict who will regress and who will progress without treatment. Some of the variation in progression of DR in pregnancy may be a result of well-known risk factors such as hypertension or inadequate glycemic control prior to pregnancy. Other pregnancy-associated retinal diseases are relatively uncommon, and their treatments are poorly characterized. Pre-existing conditions include the white dot syndromes, such as punctuate inner choroidopathy and ocular histoplasmosis syndrome, as well as chorioretinal neovascularization from many other etiologies. Retinal and chorioretinal disorders that can arise during pregnancy include central serous chorioretinopathy and occlusive vasculopathy such as retinal artery occlusion (Purtschers-like retinopathy) and retinal vein occlusion. There remains a small group that appear to be unique to pregnancy, with pre-eclampsia- and eclampsia-associated retinopathy, disseminated intravascular coagulopathy, or amniotic fluid embolism being the best described. In angiogenic retinal diseases outside of pregnancy, the use of anti-vascular endothelial growth factor (anti-VEGF agents) has proven helpful. There are no safety data about the use of anti-VEGF agents during pregnancy, and conventionally the proposed interventions have been laser photocoagulation and systemic or intravitreal injections of steroids. Most of the literature on the treatment of pregnancy associated-chorioretinal neovascularization is anecdotal.

Repeated antenatal corticosteroid treatments adversely affect neural transmission time and auditory thresholds in laboratory rats

Antenatal corticosteroid (AC) treatment is given to pregnant women at risk for preterm birth to reduce infant morbidity and mortality by enhancing lung and brain maturation. However, there is no accepted regimen on how frequently AC treatments should be given and some studies found that repeated AC treatments can cause growth retardation and brain damage. Our goal was to assess the dose-dependent effects of repeated AC treatment and estimate the critical number of AC courses to cause harmful effects on the auditory brainstem response (ABR), a sensitive measure of brain development, neural transmission and hearing loss. We hypothesized that repeated AC treatment would have harmful effects on the offspring's ABRs and growth only if more than 3 AC treatment courses were given. To test this hypothesis, pregnant Wistar rats were given either a high regimen of AC (HAC), a moderate regimen (MAC), a low regimen (LAC), or saline (SAL). An untreated control (CON) group was also used. Simulating the clinical condition, the HAC dams received 0.2mg/kg Betamethasone (IM) twice daily for 6 days during gestation days (GD) 17-22. The MAC dams received 3 days of AC treatment followed by 3 days of saline treatment on GD 17-19 and GD 20-22, respectively. The LAC dams received 1 day of AC treatment followed by 5 days of saline treatment on GD 17 and GD 18-22, respectively. The SAL dams received 6 days of saline treatment from GD 17 to 22 (twice daily, isovolumetric to the HAC injections, IM). The offspring were ABR-tested on postnatal day 24. Results indicated that the ABR's P4 latencies (neural transmission time) were significantly prolonged (worse) in the HAC pups and that ABR's thresholds were significantly elevated (worse) in the HAC and MAC pups when compared to the CON pups. The HAC and MAC pups were also growth retarded and had higher postnatal mortality than the CON pups. The SAL and LAC pups showed little or no adverse effects. In conclusion, repeated AC treatment had harmful effects on the rat offspring's ABRs, postnatal growth and survival. The prolonged ABR latencies reflect slowed neural transmission times along the auditory nerve and brainstem auditory pathway. The elevated ABR thresholds reflect hearing deficits. We concluded that repeated AC treatment can have harmful neurological, sensory and developmental effects on the rat offspring. These effects should be considered when weighing the benefits and risks of repeated AC treatment and when monitoring and managing the prenatally exposed child for possible adverse effects.

Repeated courses of antenatal corticosteroids: are there effects on the infant's auditory brainstem responses?

Our objective was to assess the effects of repeated antenatal corticosteroid treatments on the neonatal auditory brainstem response (ABR), a sensitive measure of neonatal brain maturity and auditory function. To achieve this, we performed and blindly evaluated neonatal ABRs on a subset of infants delivering within a multicenter randomized placebo-controlled clinical trial comparing single versus repeated courses of antenatal corticosteroid treatments for women at 23-31 weeks gestation who remained at increased risk for preterm birth. The women were randomly assigned to either the single or the repeated antenatal corticosteroid treatment group. Women in the repeated antenatal corticosteroid group received weekly antenatal corticosteroid treatments until 34 weeks gestation or until they reached a study-determined limited number of courses, whereas women in the single antenatal corticosteroid group received an initial course of corticosteroid followed by weekly placebo injections. We performed ABR testing on their infants prior to discharge. The latencies of waves I, III and V and the peak-to-trough amplitudes of waves I and V were compared between those in the single (n=27) and repeated antenatal corticosteroid treatment (n=24) groups. The majority of repeated antenatal corticosteroid infants (20 of 24) were exposed to ≥ 4 antenatal corticosteroid treatments. Even though gestational age was similar between our subset of single and repeated antenatal corticosteroid treatment groups, infant birth weight and length and head circumference were significantly smaller in the repeated antenatal corticosteroid group (p <0.05). Despite these differences in birth sizes, there were no significant group differences in the ABR wave latencies or amplitudes. We concluded that our repeated antenatal corticosteroid treatments, in comparison to a single treatment, did not significantly benefit or harm the neonatal ABR despite significant effects on birth size.

Long-term outcomes after repeat doses of antenatal corticosteroids

BACKGROUND

Previous trials have shown that repeat courses of antenatal corticosteroids improve some neonatal outcomes in preterm infants but reduce birth weight and increase the risk of intrauterine growth restriction. We report long-term follow-up results of children enrolled in a randomized trial comparing single and repeat courses of antenatal corticosteroids.

METHODS

Women at 23 through 31 weeks of gestation who remained pregnant 7 days after an initial course of corticosteroids were randomly assigned to weekly courses of betamethasone, consisting of 12 mg given intramuscularly and repeated once at 24 hours, or an identical-appearing placebo. We studied the children who were born after these treatments when they were between 2 and 3 years of corrected age. Prespecified outcomes included scores on the Bayley Scales of Infant Development, anthropometric measurements, and the presence of cerebral palsy.

RESULTS

A total of 556 infants were available for follow-up; 486 children (87.4%) underwent physical examination and 465 (83.6%) underwent Bayley testing at a mean (+/-SD) corrected age of 29.3+/-4.6 months. There were no significant differences in Bayley results or anthropometric measurements. Six children (2.9% of pregnancies) in the repeat-corticosteroid group had cerebral palsy as compared with one child (0.5% of pregnancies) in the placebo group (relative risk, 5.7; 95% confidence interval, 0.7 to 46.7; P=0.12).

CONCLUSIONS

Children who had been exposed to repeat as compared with single courses of antenatal corticosteroids did not differ significantly in physical or neurocognitive measures. Although the difference was not statistically significant, the higher rate of cerebral palsy among children who had been exposed to repeat doses of corticosteroids is of concern and warrants further study. (ClinicalTrials.gov number, NCT00015002 [ClinicalTrials.gov].).

The need to go beyond: evaluating antenatal corticosteroid trials with long-term outcomes

A single course of antenatal corticosteroids (ACS) reduces the risk of severe neonatal morbidity and is associated with a strong trend towards a reduced risk of abnormal neurodevelopmental outcome. However, because 50% of women given ACS remain undelivered and continue to be at risk for preterm delivery, the question remains: would these women benefit from repeated courses of ACS, and, if so, how do repeated courses of ACS affect the fetus and long-term neurodevelopmental outcome? The serious consequences of this effect on the developing brain justify the need for long-term outcome studies (beyond two years of age) before repeat courses of ACS become standard care in the management of pregnant women who are at risk of preterm delivery throughout pregnancy.

Single Versus Repeat Courses of Antenatal Steroids to Improve Neonatal Outcomes: Risks and Benefits

Recent additions to the literature provide evidence supporting the use of repeat courses of antenatal steroids. Both human and animal studies offer evidence that repeat courses of corticosteroids improve neonatal pulmonary outcomes, especially for the infants delivered at earlier gestational ages. Although there is also evidence to suggest altered neuronal maturation and intrauterine growth restriction in animals treated with repeat steroids, randomized controlled studies in humans have shown that birth weight reduction was only seen in those infants treated with 4 or more courses of corticosteroids. In addition, the reduction in neonatal birth weight and head circumference seen after multiple courses of antenatal corticosteroids normalizes by the time of hospital discharge. Studies are ongoing to investigate the 24-month post delivery physical and neurodevelopmental outcomes in infants exposed to repeat courses of antenatal corticosteroids. Although there is evidence demonstrating the safety of a single repeat, or 'rescue', dose of antenatal corticosteroids, this must be tempered against the adverse effects seen after multiple courses of weekly repeat steroids. Randomized controlled trials are needed to determine the optimal number of courses of antenatal steroids to reduce the frequency of neonatal respiratory distress syndrome (RDS) without adversely affecting other neonatal outcomes.

[Antenatal exposure to corticosteroids for fetal lung maturation and its repercussion on weight, length and head circumference in the newborn infant]

BACKGROUND AND OBJECTIVE

To study the effects of antenatal corticosteroids treatment to promote fetal lung maturation, on fetal growth, depending on the number of the courses administered.

PATIENTS AND METHOD

The study was based on data from the Spanish Collaborative Study of Congenital Malformations (ECEMC), analysing a sample of 29,557 singleton liveborn infants without congenital defects. An stratified analysis by gestational age was performed to compare the weight, length and head circumference at birth, in the exposed and unexposed infants to dexamethasone/betamethasone. To control confounding factors (year of birth, maternal age, gestational age, parity, maternal smoking and/or alcohol consumption, gestational diabetes, non-gestational diabetes and other maternal chronic diseases) we used a general linear model with random effects, being the randomised variable the place of birth.

RESULTS

The exposure to more than one course of antenatal corticosteroids resulted in a significant reduction of birth weight, length and head circumference in singleton preterm infants. The birth weight decreased by 22% (p < 0.0001), the length 5% (p = 0.002) and the head circumference 6% (p = 0.0005). The treatment with only one course reduced also significantly the weight and length but not the head circumference. In addition, we observed a significant interaction between the treatment and gestational age at birth indicating that the effect of corticosteroids is stronger in the most premature babies.

CONCLUSIONS

In this retrospective analysis, the antenatal exposure to corticosteroids to promote fetal maturation is associated with diminished weight, length and head circumference in the premature newborn infant. This negative effect was greater in those premature babies exposed to multiple courses.

Use of systemic glucocorticosteroids in pregnancy: Be alert but not alarmed

SUMMARY Concerns have been raised regarding the use of repeated courses of systemic glucocorticosteroids given to pregnant women with threatened premature labour to improve fetal lung maturity. Most worrying are animal studies showing detrimental effects on the developing brain, though human data to date are conflicting. Additional concerns relate to the fetal origins of adult diseases, particularly vascular diseases such as hypertension and atherosclerosis. It is currently recommended that obstetricians give only a single course of antenatal corticosteroids to pregnant women to enhance lung maturity instead of giving repeated doses, which was previously a common practice. Other clinicians including dermatologists, gastroenterologists and rheumatologists may have reason to provide systemic glucocorticosteroids to pregnant women. Although systemic glucocorticosteroids all cross the placenta to some degree, the extent to which they do so depends on the drug involved. The choice of systemic glucocorticosteroid for the pregnant women in light of this evolving literature is discussed.

Neurodevelopmental outcome of very low birth weight infants after multiple courses of antenatal corticosteroids

OBJECTIVE

To determine if two or more courses of antenatal corticosteroids are associated with neurodevelopmental impairment.

METHODS

All infants born at Northwestern Memorial Hospital between 1995 and 1998, who met the following criteria, were identified: birth weight < or = 1500 g, gestational age between 24 and 34 weeks, recipient of antenatal corticosteroids, and subsequent neurodevelopmental evaluation in multidisciplinary developmental evaluation clinic. The outcomes of these infants were compared according to degree of corticosteroid exposure. This study had 80% power to detect a difference in the mental development index score of 10% or a relative risk of neurodevelopmental delay of 2.5 in the group receiving at least two courses of corticosteroids.

RESULTS

Ninety-three infants were exposed to less than two full courses and 33 infants were exposed to at least two full courses of corticosteroids. The mean duration of follow-up was similar in the two groups (25 months vs 30 months, respectively, P >.05). The two groups had similar neonatal outcomes, and had no differences in any measures of neurodevelopmental outcome on follow-up.

CONCLUSION

Repeated courses of antenatal corticosteroids are not associated with increased incidence of abnormalities on subsequent neurodevelopmental outcome measures.

Prenatal and postnatal steroid therapy and child neurodevelopment

In recent years, scientific evidence has accumulated on the potential neuro-toxic effects of perinatal steroid therapy on the incompletely developed brain; therefore, much effort has been directed toward finding the optimal regimen that may reduce lung disease without incurring significant brain injury in fetuses and preterm infants. Current recommendations of the NIH endorse a single course of prenatal steroids in cases of imminent preterm delivery. Postnatal steroid therapy should be limited, according to the American Association of Pediatrics Guide-lines, to selected clinical cases after the first week of life. These cautions aim to decrease possible harmful effects that could affect short- and long-term neuro-developmental outcome in this high-risk population.

Mechanisms responsible for parturition; the use of experimental models

In this review, our knowledge, gleaned from a range of species, of what determines gestation length, how fetal maturation and birth are synchronized and how the uterotonic mechanisms are activated at birth are discussed. Accumulated data indicate that fetal glucocorticoids are involved in, but do not necessarily play a causative role in, the initiation of parturition in eutherian mammals generally. Present observations are consistent with a complex, positive regulatory interaction between estrogens, prostaglandins and oxytocin and are consistent with a role for prostaglandins as the final, common effector in myometrial activation. We are, however, left with the possibility that the initial mechanism for the timing of birth is encoded in the fetal genome and is closely linked to, and activated when, certain prerequisite developmental events have occurred in the fetus. Our understanding of these events in the sheep have led to its extensive use as an experimental model for the study of human clinical correlates of fetal maturation and development and the control of the initiation of parturition.

Cortisol enhances structural maturation of the hypoplastic fetal lung in sheep

Although exogenous corticosteroids advance structural maturation of the fetal lung, they can adversely affect fetal lung and body growth. Our aim was to determine whether cortisol, at physiological doses, can enhance structural maturation of the hypoplastic fetal lung without affecting fetal lung growth. Fetal sheep were divided into four groups (n= 5 for each) and lung hypoplasia (LH) was induced in two groups. Increasing doses of cortisol (1.5-4.0 mg) were infused into one group of fetuses with LH and one group without LH; the other two groups received saline. LH retarded structural development, reduced tropoelastin mRNA levels, reduced hydroxyproline and elastin contents, and increased active matrix metalloproteinase-2 (MMP-2) levels in the fetal lung. Cortisol infusions had no effect on fetal lung growth or body weights. In fetuses with LH, cortisol increased the percentage airspace, reduced the interalveolar wall thickness, increased alveolar number and reduced the increase in active MMP-2 levels. Thus, relatively low doses of cortisol can enhance structural maturation of the fetal lung without adversely affecting fetal lung growth. However, cortisol did not correct the abnormal deposition of elastin within the alveolar parenchyma associated with LH, indicating that secondary septal crest formation remained abnormal.

Repeated prenatal corticosteroids reduce glial fibrillary acidic protein in the ovine central nervous system

INTRODUCTION

A single course of corticosteroid reduces intracranial hemorrhage in preterm infants. The mechanism of protection is unclear. Glial fibrillary acidic protein (GFAP), expressed by astrocytes, is regulated by glucosteroids and is an important component of the cells forming the blood brain barrier. We have evaluated the effect of prenatal corticosteroid upon ovine GFAP.

METHODS

Date-mated ewes were studied in two protocols and lambs delivered on day 125 or 145 (term = 150). In the maternal injection protocol (n = 36) ewes were administered saline, single or repeated injections of corticosteroid. In the fetal injection protocol (n = 48) direct ultrasound-guided fetal injections of saline, single or repeated corticosteroid were administered, and an additional control group did not receive fetal injections. Optic nerve GFAP immunohistochemistry was performed and quantified.

RESULTS

At 125 days, repeated, but not single, administration of corticosteroid, by either maternal or fetal route, was associated with a significant reduction in GFAP (both p < 0.002); by 145 days, the deficit had recovered (both p > 0.05). The process of performing repeated fetal injections had an independent effect upon GFAP at 145 days (p = 0.002).

CONCLUSION

Repeated administration of corticosteroid results in a reduction in GFAP in the developing ovine optic nerve, with recovery demonstrated by 145 days.

Antenatal corticosteroids: the good, the bad and the unknown

PURPOSE OF REVIEW

The purpose of this review was to summarize recently published clinical and animal-based studies of antenatal corticosteroids, describe current recommendations for practice, and suggest priority areas for future research.

RECENT FINDINGS

A single course of antenatal corticosteroids is known to improve newborn lung function after preterm birth and to reduce the risk of newborn death. Current evidence from animal and clinical studies suggests that additional numbers of courses do not further improve lung function and are associated with risks of adverse consequences. These risks principally include restricted intrauterine growth, altered brain development, postnatal insulin resistance and changes to the hypothalamic-pituitary-adrenal axis.

SUMMARY

The research challenges in this field are now centred on uncovering the mechanisms by which cortisol is involved in programming the fetus for its future metabolic life, and discovering ways in which the effectiveness and safety of antenatal glucocorticoids can be enhanced.

Repeated doses of antenatal corticosteroids in animals: a systematic review

OBJECTIVE

The purpose of this review was to assess the effects of repeated doses of antenatal corticosteroids on lung and brain function and on growth restriction in animals.

STUDY DESIGN

MEDLINE and EMBASE were searched for randomized controlled trials that compared repeated doses of antenatal corticosteroids versus a single dose, with or without placebo, in pregnant animals.

RESULTS

Nineteen studies were included. The animals that were studied included sheep, monkeys, rabbits, and mice. There were 8 studies that assessed the effects of repeated doses of antenatal corticosteroids on lung function. All the studies reported improvement in lung function after repeated doses of antenatal corticosteroids. Seven studies investigated the effects of repeated doses of antenatal corticosteroids on brain or nervous system function or growth; all the studies found adverse effects with repeated doses of antenatal corticosteroids. Eleven studies looked at the effect of repeated doses of antenatal corticosteroids on fetal growth. Nine studies found evidence of fetal growth restriction with repeated doses of antenatal corticosteroids. One study assessed long-term behavioral outcomes in mice and found no effect.

CONCLUSION

Evidence from randomized controlled trials in animals suggests that repeated doses of antenatal corticosteroids may have beneficial effects in terms of lung function but may have adverse effects on brain function and fetal growth. Because of the differences between animals and humans, it is difficult to extrapolate directly the results of these studies to humans. Therefore, randomized controlled trials in humans are needed to assess the effects of repeated courses of antenatal corticosteroids for pregnant women who are at increased risk of preterm birth in terms of important perinatal, neonatal, and maternal outcomes.

Is prenatal glucocorticoid administration another origin of adult disease?

1. The intra-uterine environment is now believed to play a major role in the origin of many adult diseases. Illnesses in which there is significant 'programming' before the time of birth include hypertension, diabetes, coronary heart disease and stroke. Acting on a genetic predisposition, intra-uterine triggers appear to programme the individual's metabolism and endocrine milieu and, after birth, these risk factors are then either amplified or minimized by environmental influences. The triggers operative during fetal life that have been studied most extensively are undernutrition and glucocorticoid exposure. 2. Over the past decade, a series of studies in sheep have focused on the perinatal and life-long consequences of glucocorticoid exposure in mid- to late-pregnancy. These studies in the sheep model have shown that maternal injections with glucocorticoids, in a manner similar to clinical treatment for women at risk of preterm birth, enhance fetal lung maturation, but were also associated with developmental and other functional alterations that are of concern. With weekly doses to the mother, there is restricted fetal growth, delayed myelination of the central nervous system, altered blood pressure soon after birth and increased insulin response to glucose challenge in early adulthood. If the glucocorticoids are given to the fetus by ultrasound-guided intramuscular injection, rather than to the mother, the effects on lung maturation are similar, but growth is spared and blood pressure after birth is unaltered. Increased insulin response to glucose challenge occurs in early adulthood with glucocorticoid by either route and is independent of growth restriction. 3. The findings in experimental animals are supported by studies of children in the Western Australian Preterm Infant Follow-up Study. Multivariate analyses have shown that increasing the number of glucocorticoid exposures, for the purpose of enhancing lung maturation prior to preterm birth, is associated with reduced birthweight and behavioural disorders at 3 years of age. 4. The results of these animal and clinical studies provide further support for a role of prenatal glucocorticoid exposure in triggering predisposition to adult disease. Further exploration of these models is expected to uncover the mechanisms and lead to effective strategies that may underpin clinical interventions.

Antenatal corticosteroids for preterm birth

A single course of antenatal corticosteroids is a rare example of a treatment that yields both a health benefit and a cost savings. This article reviews the history and background of antenatal corticosteroids, its use in clinical practice and the controversy today regarding the use of multiple courses of antenatal corticosteroids.

Repeated ultrasound guided fetal injections of corticosteroid alter nervous system maturation in the ovine fetus

INTRODUCTION

Recent studies in sheep have shown that repeated maternal injections of betamethasone are associated with adverse effects within the nervous system. Repeated fetal injections of betamethasone achieve serial improvements in preterm lung function in sheep and are a possible alternative to repeated maternal therapy. We have evaluated the effect of repeated fetal administration of betamethasone on nervous system maturation in an ovine model.

METHODS

Date-mated ewes (n = 48) were randomized to receive ultrasound-guided fetal injections of betamethasone or saline between days 104 to 124 of gestation and were delivered by cesarean section on day 125 or 145 (term = 150). Optic and sciatic nerves were prepared for light and electronmicroscopy. Eye diameters were measured and transverse sections of retinae were evaluated. Data were analyzed using a mixed model analysis of variance.

RESULTS

Repeated fetal administration of corticosteroid did not significantly affect optic nerve myelination but resulted in significant delays in sciatic axonal growth (p < 0.02) and retinal maturation (p < 0.04). The process of performing repeated fetal injections also significantly affected some retinal parameters.

CONCLUSION

Repeated fetal administration of betamethasone alters some aspects of nervous system maturation in sheep. It is premature to plan trials of repeated fetal corticosteroid therapy in humans.

Repeated prenatal corticosteroid administration delays astrocyte and capillary tight junction maturation in fetal sheep

Glucocorticoids are powerful regulators of cell differentiation and maturation. Their synthetic counterparts, the corticosteroids, are used widely in obstetric practice to enhance fetal lung maturation in cases of threatened preterm birth. Here we examined the effects of repeated corticosteroid administration on astrocyte and capillary tight junction development in the fetal sheep brain, selecting the corpus callosum for analysis. Pregnant ewes were given saline or betamethasone (0.5 mg/kg) at 104, 111, 118 and 124 days gestation. Lambs were delivered at term, terminally anaesthetized and transcardially perfused. Transverse semi-thin sections of the corpus callosum were cut and immuno-stained with antibody against glial fibrillary acidic protein (GFAP). Ultra-thin sections were examined in the electron microscope. The percentage area of GFAP staining was reduced in the corticosteroid-treated group compared to control (5.2 vs. 8.7%, P<0.05). The expression of GFAP in peri-capillary and parenchymal astrocytes was also reduced compared to control (peri-capillary: 3.0 vs. 9.5 microm2; parenchymal: 14.6 vs. 29.4 microm2, P<0.05). Furthermore, capillary tight junction maturation was delayed compared to control. Immature 'type II' junctions were more common in the corticosteroid-treated group (63 vs. 22%, P<0.05), whereas more mature 'type III' junctions were less common (27 vs. 65%, P<0.05). Our data suggest that repeated corticosteroids delay both astrocyte and capillary tight junction maturation. The implications for clinical practice are as yet unknown.

Antenatal glucocorticoids and growth: single versus multiple doses in animal and human studies

In recent years, many clinicians have prescribed repeated courses of glucocorticoids to pregnant women at risk of early preterm birth. The published literature has provided reassurance from randomized controlled trials that single-course treatment improves postnatal lung function without deleterious consequences, but we do not yet have data from randomized trials designed specifically to investigate the effects of repeated courses. Data from animal studies have, for many years, provided evidence that prenatal exposure to glucocorticoids restricts fetal growth and, more recently, has suggested a role in programming the individual to adult disease. Multivariate analyses from non-randomized cohorts have also suggested associations between repeated treatments and reduced birth weight, but we await results from randomized controlled trials currently in progress to provide more definitive answers. Regardless of any effect on growth, the possibility that adult health and disease may be programmed by fetal exposure to glucocorticoids will ensure our need to balance the ability of these agents to improve newborn survival with the potential consequences in later life.