Long-term effects of betamethasone on fetal development

Gestational protein restriction alters early amygdala neurochemistry in male offspring

BACKGROUND

Gestational protein intake restriction-induced long-lasting harmful outcomes in the offspring's organs and systems. However, few studies have focused on this event's impact on the brain's structures and neurochemical compounds.

AIM

The present study investigated the effects on the amygdala neurochemical composition and neuronal structure in gestational protein-restricted male rats' offspring.

METHODS

Dams were maintained on isocaloric standard rodent laboratory chow with regular protein [NP, 17%] or low protein content [LP, 6%]. Total cells were quantified using the Isotropic fractionator method, Neuronal 3D reconstruction, and dendritic tree analysis using the Golgi-Cox technique. Western blot and high-performance liquid chromatography performed neurochemical studies.

RESULTS

The gestational low-protein feeding offspring showed a significant decrease in birth weight up to day 14, associated with unaltered brain weight in youth or adult progenies. The amygdala cell numbers were unchanged, and the dendrites length and dendritic ramifications 3D analysis in LP compared to age-matched NP progeny. However, the current study shows reduced amygdala content of norepinephrine, epinephrine, and dopamine in LP progeny. These offspring observed a significant reduction in the amygdala glucocorticoid (GR) and mineralocorticoid (MR) receptor protein levels. Also corticotrophin-releasing factor (CRF) amygdala protein content was reduced in 7 and 14-day-old LP rats.

CONCLUSION

The observed amygdala neurochemical changes may represent adaptation during embryonic development in response to elevated fetal exposure to maternal corticosteroid levels. In this way, gestational malnutrition stress can alter the amygdala's neurochemical content and may contribute to known behavioral changes induced by gestational protein restriction.

Maternal Betamethasone for Prevention of Respiratory Distress Syndrome in Neonates: Population Pharmacokinetic and Pharmacodynamic Approach

Despite antenatal corticosteroids therapy, respiratory distress syndrome (RDS) is still a leading cause of neonatal morbidity and mortality in premature newborns. To date, the relationship between in utero fetal drug exposure and occurrence of RDS remains poorly evaluated. This study aims to describe the pharmacokinetics of betamethasone in pregnant women and to evaluate the transplacental drug transfer and administration scheme for the prevention of RDS. Pregnant women > 27 weeks' gestation and who received at least a single dose of betamethasone for prevention of RDS were enrolled. Maternal, cord blood, and amniotic fluid betamethasone time-courses were analyzed using the Monolix software. A total of 220 maternal blood, 56 cord blood, and 26 amniotic fluid samples were described by a two-compartment model with two effect compartments linked by rate transfer constants. Apparent clearances and volumes of distribution parameters were allometrically scaled for a 70 kg third trimester pregnant woman. The impact of a twin pregnancy was found to increase maternal clearance by 28%. Using a fetal-to-mother exposure ratio, the median (95% confidence interval (CI)) transplacental transfer of betamethasone was estimated to 35% (95% CI 0.11-0.67). After adjustment for gestational age and twin pregnancy, RDS was found to be associated to the time spent in utero below quantifiable concentrations (i.e., < 1 ng/mL): odds ratio of 1.10 (95% CI 1.01-1.19) per day increase (P < 0.05). Trying to take into account both efficacy and safety, we simulated different dosing schemes in order to maintain a maximum of fetuses above 1 ng/mL without exceeding the total standard dose.

Is there a definite relationship between placental mTOR signaling and fetal growth?

Fetal growth restriction and overgrowth are common obstetrical complications that result in adverse perinatal outcomes and long-term health risks later in life, including neurodevelopmental dysfunction and adult metabolic syndrome. The placenta plays a critical role in the nutrition transfer from mother to fetus and even exerts adaptive mechanism when the fetus is under poor developmental conditions. The mammalian/mechanistic target of rapamycin (mTOR) signaling serves as a critical hub of cell growth, survival, and metabolism in response to nutrients, growth factors, energy, and stress signals. Placental mTOR signaling regulates placental function, including oxygen and nutrient transport. Therefore, placental mTOR signaling is hypothesized to have a positive relationship with fetal growth. In this review, we summarize that most studies support the current evidence that there is connection between placental mTOR signaling and abnormal fetal growth; however, but more studies should be performed following a vigorous and unanimous method for assessment to determine placental mTOR activity.

Models of Intrauterine growth restriction and fetal programming in rabbits

Intrauterine growth restriction (IUGR) affects approximately 10% of human pregnancies globally and has immediate and life-long consequences for offspring health. However, the mechanisms underlying the pathogenesis of IUGR and its association with later health and disease outcomes are poorly understood. To address these knowledge gaps, the use of experimental animals is critically important. Since the 50's different environmental, pharmacological, and surgical manipulations have been performed in the rabbit to improve our knowledge of the control of fetal growth, fetal responses to IUGR, and mechanisms by which offspring may be programmed by an adverse gestational environment. The purpose of this review is therefore to summarize the utility of the rabbit as a model for IUGR research. It first summarizes the knowledge of prenatal and postnatal development in the rabbit and how these events relate to developmental milestones in humans. It then describes the methods used to induce IUGR in rabbits and the knowledge gained about the mechanisms determining prenatal and postnatal outcomes of the offspring. Finally, it discusses the application of state of the art approaches in the rabbit, including high-resolution ultrasound, magnetic resonance imaging, and gene targeting, to gain a deeper integrative understanding of the physiological and molecular events governing the development of IUGR. Overall, we hope to engage and inspire investigators to employ the rabbit as a model organism when studying pregnancy physiology so that we may advance our understanding of mechanisms underlying IUGR and its consequences in humans and other mammalian species.

Full versus half dose of antenatal betamethasone to prevent severe neonatal respiratory distress syndrome associated with preterm birth: study protocol for a randomised, multicenter, double blind, placebo-controlled, non-inferiority trial (BETADOSE)

BACKGROUND

Although antenatal betamethasone is recommended worldwide for women at risk of preterm delivery, concerns persist regarding the long-term effects associated with this treatment. Indeed, adverse events, mainly dose-related, have been reported. The current recommended dose of antenatal betamethasone directly derives from sheep experiments performed in the late 60's and has not been challenged in 45 years. Therefore, randomized trials evaluating novel dose regimens are urgently needed.

METHODS

A randomised, double blind, placebo-controlled, non-inferiority trial will be performed in 37 French level 3 maternity units. Women with a singleton pregnancy at risk of preterm delivery before 32 weeks of gestation having already received a first 11.4 mg injection of betamethasone will be randomised to receive either a second injection of 11.4 mg betamethasone (full dose arm) or placebo (half dose arm) administered intramuscularly 24 h after the first injection. The primary binary outcome will be the occurrence of severe respiratory distress syndrome (RDS), defined as the need for exogenous intra-tracheal surfactant in the first 48 h of life. Considering that 20% of the pregnant women receiving the full dose regimen would have a neonate with severe RDS, 1571 patients in each treatment group are required to show that the half dose regimen is not inferior to the full dose, that is the difference in severe RDS rate do not exceed 4% (corresponding to a Relative Risk of 20%), with a 1-sided 2.5% type-1 error and a 80% power. Interim analyses will be done after every 300 neonates who reach the primary outcome on the basis of intention-to-treat, using a group-sequential non-inferiority design.

DISCUSSION

If the 50% reduced antenatal betamethasone dose is shown to be non-inferior to the full dose to prevent severe RDS associated with preterm birth, then it should be used consistently in women at risk of preterm delivery and would be of great importance to their children.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT 02897076 (registration date 09/13/2016).

Efficacy and safety of antenatal steroids

Antenatal steroids (ANS) are among the most important and widely utilized interventions to improve outcomes for preterm infants. A significant body of evidence demonstrates improved outcomes in preterm infants (24-34 wk) delivered between 1 and 7 days after the administration of a single course of ANS. Moreover, ANS have the advantage of being widely available, low cost, and easily administered via maternal intramuscular injection. The use of ANS to mature the fetal lung is, however, not without contention. Their use in pregnancy is not FDA approved, and treatment doses and regimens remain largely unoptimized. Their mode of use varies considerably between countries, and there are lingering concerns regarding the safety of exposing the fetus to high doses of exogenous steroids. A significant proportion of women deliver outside the 1- to 7-day therapeutic window after ANS treatment, and this delay may be associated with an increased risk of adverse outcomes for both mother and baby. Today, animal-based studies are one means by which key questions of dosing and safety relating to ANS may be resolved, allowing for further refinement(s) of this important therapy. Complementary approaches using nonhuman primates, sheep, and rodents have provided invaluable advances to our understanding of how exogenous steroid exposure impacts fetal development. Focusing on these three major model groups, this review highlights the role of three key animal models (sheep, nonhuman primates, rodents) in the development of antenatal steroid therapy, and provides an up-to-date synthesis of current efforts to refine this therapy in an era of personalised medicine.

Repeat Antenatal Betamethasone and Cardiometabolic Outcomes

BACKGROUND

Repeat dose(s) of antenatal betamethasone are recommended for women at <32 weeks with ongoing risk of preterm birth. However, there is concern that use of repeat dose(s) in fetal growth restriction (FGR) may increase the risk of later cardiometabolic disease.

METHODS

We undertook secondary analysis of data from the Australasian Collaborative Trial of Repeat Doses of Corticosteroids Midchildhood Outcome Study to determine if FGR influences the effect of repeat betamethasone on growth and cardiometabolic function. At 6 to 8 years, children underwent anthropometry, dual energy x-ray absorptiometry, intravenous glucose tolerance testing, ambulatory blood pressure monitoring, and spirometry. FGR was defined as severe FGR at entry, cesarean delivery for FGR, or customized birth weight below the third centile.

RESULTS

Of 266 children assessed, FGR occurred in 43 of 127 (34%) exposed to repeat betamethasone and 44 of 139 (32%) exposed to placebo. There was an interaction between FGR and repeat betamethasone treatment for the effect on height (z score mean difference [95% confidence interval]; FGR: 0.59 [0.01 to 1.17]; non-FGR: -0.29 [-0.69 to 0.10]; P = .01). However, FGR did not influence the effect of repeat betamethasone on cardiometabolic function, which was similar in treatment groups, both in FGR and non-FGR subgroups.

CONCLUSIONS

Repeat antenatal betamethasone treatment had no adverse effects on cardiometabolic function, even in the presence of FGR. It may have a positive effect on height in FGR. Clinicians should use repeat doses of antenatal corticosteroids when indicated before preterm birth, regardless of FGR, in view of the associated neonatal benefits.

The window of improved neonatal respiratory compliance after rescue antenatal steroids

OBJECTIVE

To evaluate whether premature infants delivered ≤7 days after rescue antenatal steroid treatment (ideal treatment) have increased passive respiratory compliance compared to those delivered >7 days after treatment (remote treatment).

METHODS

Secondary analysis of a randomized trial of rescue antenatal steroids on respiratory compliance. Infants in the treatment group were stratified by the interval between rescue antenatal steroids and delivery. We then compared the respiratory compliance in the ideal vs. remote groups.

RESULTS

Forty-four women (56 infants) received rescue antenatal steroids. Forty-nine infants had evaluable respiratory compliance measurements, with 27 (GA 30.1 weeks, BW 1362 g) "ideally" treated, and 22 (GA 33.8 weeks, BW 2248 g) "remotely" treated. Respiratory compliance was significantly higher for the ideal compared to the remote group (1.32 vs. 1.06 mL/cm H2O/kg; p = 0.037).

CONCLUSION

Infants treated with rescue antenatal steroids have a significantly higher respiratory compliance if delivery occurs within 7 days after treatment.

Pulmonary function and outcomes in infants randomized to a rescue course of antenatal steroids

BACKGROUND/OBJECTIVE

Our objective was to obtain follow-up pulmonary function testing and assessment of clinical respiratory outcomes, at 1-2 years, in preterm infants whose mothers were randomized to a single rescue course of antenatal steroids (AS) versus placebo.

METHODS

Follow-up of a randomized, double-blinded trial. In the original trial pregnant women ≥14 days after initial course of AS were randomized to rescue AS or placebo. Pulmonary function testing and a standardized respiratory questionnaire were obtained at 1-2 years of corrected age. Respiratory compliance (Crs) was measured with the single-breath occlusion and functional residual capacity (FRC) with the nitrogen washout method. Analysis was by intention-to-treat.

RESULTS

A total of 96 (87%) of available survivors were administered a respiratory questionnaire. Seventy-seven percent of available patients had pulmonary function testing performed. There was no significant difference between groups in incidence of wheezing, asthma, respiratory syncytial virus infection, respiratory readmissions, use of bronchodilators or other medications, or in measurements of pulmonary function. There was also no significant difference in corrected age at study, race, gender, or length at the time of pulmonary function testing. Infants in the rescue group had a comparable mean FRC (249.4 mL vs 246.2 mL; adjusted 95%CI for difference -15.45, 38.20; P = 0.37) versus placebo. There were no differences in tidal volume or Crs.

CONCLUSION

A rescue course of AS significantly increases Crs within 72 h of age and decreases oxygen need in newborn infants, without an adverse impact on pulmonary function or clinical respiratory outcomes at 1-2 years of age [NCT00669383].

Measurement of betamethasone concentration in maternal serum treated for fetal lung maturity; Is it feasible?

BACKGROUND

The association between maternal serum concentration of betamethasone given for fetal lung maturity and perinatal outcome has not been investigated. This may be due to an absence of a reliable method for measuring serum betamethasone concentrations. We aimed in the current study to assess the feasibility of a specific ELISA kit to measure the concentrations of betamethasone in maternal serum and to examine the trend of sequential measurements after a course of betamethasone for fetal lung maturity.

METHODS

Pregnant women at risk for preterm birth who received betamethasone between 24 and 34 weeks of gestation were prospectively included. Serum concentrations were determined before administering betamethasone (baseline), and 36 hours, 48 hours, 72 hours, and 5 to 7 days after the 1(st) dose. Betamethasone concentration in samples was determined using Corticosteroid ELISA kit. The Friedman test was used to test whether there were significant differences between the measurements.

RESULTS

Five singleton pregnancies were included. Using the ELISA kit, betamethasone concentration in maternal serum samples was obtained for all women. Among the five measurements performed, the concentration was highest at 36 hours after the 1(st) dose and close to baseline at the 5(th) measurement performed after 5 to 7 days (p < 0.05). Serum concentration varied at each time point between the five women but similar trend was observed.

CONCLUSION

Betamethasone concentration is measurable in the serum of pregnant women with this ELISA kit.

Increased maternal nighttime cortisol concentrations in late gestation alter glucose and insulin in the neonatal lamb

Previous studies in our laboratory have shown that a modest chronic increase in maternal cortisol concentrations impairs maternal glucose metabolism and increases the incidence of perinatal stillbirth. The dramatic outcomes prevented our ability to study the effects of maternal hypercortisolemia on neonatal growth, glucose metabolism, and hypothalamo–pituitary–adrenal axis response. Therefore, we developed a model in which pregnant ewes are infused for 12 h/day at 0.5 mg·kg^–1·day^–1 from day 115 of gestation until delivery (˜145), elevating nighttime plasma cortisol concentrations. This pattern of elevation of cortisol mimics that in patients with elevated evening cortisol concentrations, as in Cushing’s syndrome or chronic depression. Plasma cortisol, glucose, insulin, and electrolytes were measured during pregnancy and postpartum in control and cortisol-infused ewes and their postnatal lambs for the first 14 days after delivery. Neonatal growth and plasma ACTH, aldosterone, renin activity, and electrolytes, and organ weights at 14 days of age were also measured. Infusion of cortisol increased maternal plasma cortisol during pregnancy but not postpartum, and did not alter neonatal ACTH or cortisol. Although maternal glucose and insulin concentrations were not changed by the maternal infusion of cortisol, neonatal plasma glucose was increased and plasma insulin was decreased compared to those in the control group. Neonatal ponderal index and kidney weight were reduced, left ventricular wall thickness was increased, and plasma sodium and creatinine were increased after maternal cortisol infusion. These results suggest that excess maternal cortisol concentrations in late gestation alter growth, glucose and insulin regulation, and organ maturation in the neonate.

Glucocorticoid exposure altered angiogenic factor expression via Akt/mTOR pathway in rat placenta

During pregnancy, glucocorticoids (GCs) are used for fetal lung maturation in women at risk of preterm labor. Exogenous GCs do not have exclusively beneficial effects and repeated use of GCs remains controversial. It has been observed that GC exposed rats have smaller placentas and intrauterine growth retarded fetuses. In this study, we questioned whether or not glucocorticoids effect placental angiogenesis mechanisms. One of the most important signaling pathways among several downstream of VEGFR-2 is PI3K/Akt which subsequently activates the mammalian target of rapamycin. Therefore, we hypothesized that overexposure to GCs may adversely affect placental angiogenesis mechanisms by regulating pro-angiogenic factors and their receptors via Akt/mTOR pathway. According to our results Dexamethasone, a synthetic glucocorticoid, administration led to a decrease in VEGF, PIGF expression during pregnancy. VEGFR2 expression was first decreased at gestational day 14 and afterwards increased at gestational days 16, 18 and 20 in rat placentas. These results are in accordance with the reduced phosphorylation of Akt, 4EBP1 and p70S6K. Dexamethasone injection also resulted in a reduction of VEGF, VEGFR1, and VEGFR2 mRNA expression at gestational days 14 and 20, but PIGF mRNA expression was not altered. Growth retarded fetuses seen in Dexamethasone treated pregnancies, may be a result of altered angiogenic factor expression of the placenta mediated via altered mTOR pathway signaling.

Early-life glucocorticoid exposure: the hypothalamic-pituitary-adrenal axis, placental function, and long-term disease risk

An adverse early-life environment is associated with long-term disease consequences. Adversity early in life is hypothesized to elicit developmental adaptations that serve to improve fetal and postnatal survival and prepare the organism for a particular range of postnatal environments. These processes, although adaptive in their nature, may later prove to be maladaptive or disadvantageous if the prenatal and postnatal environments are widely discrepant. The exposure of the fetus to elevated levels of either endogenous or synthetic glucocorticoids is one model of early-life adversity that contributes substantially to the propensity of developing disease. Moreover, early-life glucocorticoid exposure has direct clinical relevance because synthetic glucocorticoids are routinely used in the management of women at risk of early preterm birth. In this regard, reports of adverse events in human newborns have raised concerns about the safety of glucocorticoid treatment; synthetic glucocorticoids have detrimental effects on fetal growth and development, childhood cognition, and long-term behavioral outcomes. Experimental evidence supports a link between prenatal exposure to synthetic glucocorticoids and alterations in fetal development and changes in placental function, and many of these alterations appear to be permanent. Because the placenta is the conduit between the maternal and fetal environments, it is likely that placental function plays a key role in mediating effects of fetal glucocorticoid exposure on hypothalamic-pituitary-adrenal axis development and long-term disease risk. Here we review recent insights into how the placenta responds to changes in the intrauterine glucocorticoid environment and discuss possible mechanisms by which the placenta mediates fetal hypothalamic-pituitary-adrenal development, metabolism, cardiovascular function, and reproduction.

Elevated glucocorticoids during ovine pregnancy increase appetite and produce glucose dysregulation and adiposity in their granddaughters in response to ad libitum feeding at 1 year of age

OBJECTIVE

Synthetic glucocorticoids (sGCs) are administered to women threatening preterm labor. We have shown multigenerational endocrine and metabolic effects of fetal sGC exposure. We hypothesized that sGC exposure would alter the second filial generation (F2) offspring neonatal leptin peak that controls development of appetitive behavior with metabolic consequences.

STUDY DESIGN

F0 nulliparous ewes were bred to a single ram. Beginning at day 103 of gestation (term 150 days), dexamethasone (DEX) ewes received 4 injections of 2 mg DEX intramuscularly, 12 hours apart. Control ewes received saline. Ewes lambed naturally. At 22 months of age, F1 offspring were mated to produce F2 offspring. At 10 months of age, F2 female offspring were placed on an ad libitum feeding challenge for 12 weeks.

RESULTS

DEX F2 female offspring did not show a postnatal leptin peak and their plasma cortisol concentration was elevated in the first days of life. During the feeding challenge, DEX F2 offspring consumed 10% more feed and gained 20% more weight compared with control F2 offspring. At the end of the feeding challenge, DEX F2 offspring had greater adiposity compared with control F2 offspring. F2 sGC offspring showed impaired insulin secretion in response to an intravenous glucose tolerance test.

CONCLUSION

sGC administration to F0 mothers eliminates the neonatal leptin peak in F2 female offspring potentially by inhibition caused by elevated cortisol in the DEX F2 offspring. F2 offspring showed increased appetite, weight gain, and adiposity during an ad libitum feeding challenge accompanied by decreased insulin response to an intravenous glucose tolerance test.

Short- and long-term effects of exposure to natural and synthetic glucocorticoids during development

1.Glucocorticoids (GCs) are necessary for fetal development, but clinical and experimental studies suggest that excess exposure may be detrimental to health in both the short and longer term. 2.Exposure of the fetus to synthetic GCs can occur if the mother has a medical condition requiring GC therapy (e.g. asthma) or if she threatens to deliver her baby prematurely. Synthetic GCs can readily cross the placenta and treatment is beneficial, at least in the short term, for maternal health and fetal survival. 3.Maternal stress during pregnancy can raise endogenous levels of the natural GC cortisol. A significant proportion of the cortisol is inactivated by the placental 'GC barrier'. However, exposure to severe stress during pregnancy can result in increased risk of miscarriage, low birth weight and behavioural deficits in children. 4.Animal studies have shown that excess exposure to both synthetic and natural GCs can alter normal organ development, including that of the heart, brain and kidney. The nature and severity of the organ impairment is dependent upon the timing of exposure and, in some cases, the type of GC used and the sex of the fetus. 5.In animal models, exposure to elevated GCs during pregnancy has been associated with adult-onset diseases, including elevated blood pressure, impaired cardiac and vascular function and altered metabolic function.

Multigenerational effects of fetal dexamethasone exposure on the hypothalamic-pituitary-adrenal axis of first- and second-generation female offspring

OBJECTIVE

Synthetic glucocorticoid (sGC) administration to women threatening preterm delivery increases neonatal survival. Evidence shows that fetal exposure to glucocorticoid levels higher than appropriate for current maturation programs offspring development. We examined fetal sGC multigenerational effects on F1 and F2 female offspring hypothalamo-pituitary-adrenal axis (HPAA) function.

STUDY DESIGN

At 0.7 gestation, pregnant F0 ewes received 4 dexamethasone injections (2 mg, approximately 60 μg/kg(-1) per day(-1), 12 hours apart) or saline (control). F1 female offspring were bred to produce F2 female offspring. Postpubertal HPAA function was tested in F1 and F2 ewes.

RESULTS

F1 and F2 ewe lambs showed reduced birthweight and morphometrics. Dexamethasone increased baseline but reduced stimulated HPAA activity in F1 and F2 female offspring.

CONCLUSION

This is the first demonstration that sGC doses in the clinical range have multigenerational effects on hypothalamo-pituitary-adrenal activity in a precocial species, indicating the need for the study of long-term effects of fetal sGC exposure.

Gestational protein restriction induces CA3 dendritic atrophy in dorsal hippocampal neurons but does not alter learning and memory performance in adult offspring

Studies have demonstrated that nutrient deficiency during pregnancy or in early postnatal life results in structural abnormalities in the offspring hippocampus and in cognitive impairment. In an attempt to analyze whether gestational protein restriction might induce learning and memory impairments associated with structural changes in the hippocampus, we carried out a detailed morphometric analysis of the hippocampus of male adult rats together with the behavioral characterization of these animals in the Morris water maze (MWM). Our results demonstrate that gestational protein restriction leads to a decrease in total basal dendritic length and in the number of intersections of CA3 pyramidal neurons whereas the cytoarchitecture of CA1 and dentate gyrus remained unchanged. Despite presenting significant structural rearrangements, we did not observe impairments in the MWM test. Considering the clear dissociation between the behavioral profile and the hippocampus neuronal changes, the functional significance of dendritic remodeling in fetal processing remains undisclosed.

Growth and insulin dynamics in two generations of female offspring of mothers receiving a single course of synthetic glucocorticoids

OBJECTIVE

Synthetic glucocorticoid administration to women threatening preterm delivery increases neonatal survival. However, mounting evidence shows that fetal exposure to glucocorticoid levels higher than appropriate for current maturation adversely programs offspring development. We examined fetal synthetic glucocorticoid multigenerational metabolic effects on F1 and F2 female offspring.

STUDY DESIGN

At 0.7 gestation, pregnant F0 ewes received 4 injections of dexamethasone (2 mg, approximately 60 ug.kg(-1) day(-1) 12 hours apart) or saline (control). F1 female offspring were bred to produce F2 female offspring. Postpubertal pancreatic β-cell function was tested in F1 and F2 by intravenous glucose tolerance test.

RESULTS

F1 and F2 ewe lambs showed reduced birthweight and morphometrics, and similar increased fasting glucose and decreased intravenous glucose tolerance test β-cell response.

CONCLUSION

This is the first demonstration of multigenerational programming of later life β-cell response by clinically relevant doses of synthetic glucocorticoid indicating the need for study of long-term effects of fetal exposure to synthetic glucocorticoid.

Sex-dependent cognitive performance in baboon offspring following maternal caloric restriction in pregnancy and lactation

In humans a suboptimal diet during development has negative outcomes in offspring. We investigated the behavioral outcomes in baboons born to mothers undergoing moderate maternal nutrient restriction (MNR). Maternal nutrient restriction mothers (n = 7) were fed 70% of food eaten by controls (CTR, n = 12) fed ad libitum throughout gestation and lactation. At 3.3 ± 0.2 (mean ± standard error of the mean [SEM]) years of age offspring (controls: female [FC, n = 8], male [MC, n = 4]; nutrient restricted: female [FR, n = 3] and male [MR, n = 4]) were administered progressive ratio, simple discrimination, intra-/extra-dimension set shift and delayed matching to sample tasks to assess motivation, learning, attention, and working memory, respectively. A treatment effect was observed in MNR offspring who demonstrated less motivation and impaired working memory. Nutrient-restricted female offspring showed improved learning, while MR offspring showed impaired learning and attentional set shifting and increased impulsivity. In summary, 30% restriction in maternal caloric intake has long lasting neurobehavioral outcomes in adolescent male baboon offspring.

Prenatal betamethasone exposure has sex specific effects in reversal learning and attention in juvenile baboons

OBJECTIVE

We investigated effects of 3 weekly courses of fetal betamethasone (βM) on motivation and cognition in juvenile baboon offspring utilizing the Cambridge Neuropsychological Test Automated Battery.

STUDY DESIGN

Pregnant baboons (Papio species) received 2 injections of saline control or 175 μg/kg βM 24 hours apart at 0.6, 0.65, and 0.7 gestation. Offspring (saline control female, n = 7 and saline control male, n = 6; βM female [FβM], n = 7 and βM male [MβM], n = 5) were studied at 2.6-3.2 years with a progressive ratio test for motivation, simple discriminations and reversals for associative learning and rule change plasticity, and an intra/extradimensional set-shifting test for attention allocation.

RESULTS

βM exposure decreased motivation in both sexes. In intra/extradimensional testing, FβM made more errors in the simple discrimination reversal (mean difference of errors [FβM - MβM] = 20.2 ± 9.9; P ≤ .05), compound discrimination (mean difference of errors = 36.3 ± 17.4; P ≤ .05), and compound reversal (mean difference of errors = 58 ± 23.6; P < .05) stages as compared to the MβM offspring.

CONCLUSION

This central nervous system developmental programming adds growing concerns of long-term effects of repeated fetal synthetic glucocorticoid exposure. In summary, behavioral effects observed show sex-specific differences in resilience to multiple fetal βM exposures.

Pre- and/or postnatal protein restriction in rats impairs learning and motivation in male offspring

Suboptimal developmental environments program offspring to lifelong health complications including affective and cognitive disorders. Little is known about the effects of suboptimal intra-uterine environments on associative learning and motivational behavior. We hypothesized that maternal isocaloric low protein diet during pregnancy and lactation would impair offspring associative learning and motivation as measured by operant conditioning and the progressive ratio task, respectively. Control mothers were fed 20% casein (C) and restricted mothers (R) 10% casein to provide four groups: CC, RR, CR, and RC (first letter pregnancy diet and second letter lactation diet), to evaluate effects of maternal diet on male offspring behavior. Impaired learning was observed during fixed ratio-1 operant conditioning in RC offspring that required more sessions to learn vs. the CC offspring (9.4±0.8 and 3.8±0.3 sessions, respectively, p<0.05). Performance in fixed ratio-5 conditioning showed the RR (5.4±1.1), CR (4.0±0.8), and RC (5.0±0.8) offspring required more sessions to reach performance criterion than CC offspring (2.5±0.5, p<0.05). Furthermore, motivational effects during the progressive ratio test revealed less responding in the RR (48.1±17), CR (74.7±8.4), and RC (65.9±11.2) for positive reinforcement vs. the CC offspring (131.5±7.5, p<0.05). These findings demonstrate negative developmental programming effects due to perinatal isocaloric low protein diet on learning and motivation behavior with the nutritional challenge in the prenatal period showing more vulnerability in offspring behavior.

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.

Seizures during pregnancy modify the development of hippocampal interneurons of the offspring

We investigated the effect of epileptic seizures during pregnancy on hippocampal expression of calcium-binding proteins in the offspring. Female Wistar rats were submitted to the pilocarpine model and mated during the chronic period. Seizure frequency was monitored over the entire pregnancy. Pups were perfused at postnatal days 6 and 13, and the brains processed for Nissl staining and immunohistochemistry for NeuN, calbindin, calretinin, and parvalbumin. Number of stained cells in the hippocampus was estimated through stereological methods. Our results showed a decrease in epileptic seizure frequency during pregnancy. No differences were observed in NeuN-positive, CR-positive cells, and Nissl-stained hippocampal neurons between the groups. However, there was a significant decrease in calbindin-positive cells (P=0.005) and a significant increase in parvalbumin-positive cells (P=0.02) in the experimental group when compared with the control group. These results suggest that seizures during pregnancy affect the development of specific hippocampal interneurons of the offspring.

Dose-response effects of betamethasone on maturation of the fetal sheep lung

OBJECTIVE

Glucocorticoid administration to women in preterm labor improves neonatal mortality and morbidity. Fetal exposure to glucocorticoid levels higher than those appropriate to the current gestational stage has multiple organ system effects. Some, eg, fetal hypertension, are maximal at lower than the clinical dose. We hypothesized that the clinical dose has supramaximal lung maturational effects.

STUDY DESIGN

We evaluated the full, half, and quarter clinical betamethasone dose (12 mg/70 kg or 170 microg/kg intramuscularly twice 24 hours apart) on fetal sheep lung pressure volume curves (PVC) after 48 hours' exposure at 0.75 gestation. We measured key messenger RNAs and protein products that affect lung function and total lung dipalmitoyl phosphatidyl choline.

RESULTS

Full and half doses had similar PVC and total lung dipalmitoyl phosphatidyl choline effects. Messenger RNA for surfactant proteins A, B, and D and elastin increased in a dose-dependent fashion.

CONCLUSION

Half the clinical betamethasone dose produces maximal PVC improvement in fetal sheep at 0.75 gestation.

Effects of maternal dexamethasone treatment in early pregnancy on pituitary-adrenal axis in fetal sheep

Fetal exposure to elevated levels of bioactive glucocorticoids early in gestation, as in suspected cases of congenital adrenal hyperplasia, may result in adverse neurological events. Fetal hypothalamic-pituitary-adrenal development and function may be involved. We investigated immediate and long-term effects of maternal dexamethasone (DEX) administration early in pregnancy on fetal growth and pituitary-adrenal activity in sheep. Pregnant ewes carrying singleton fetuses (total n = 119) were randomized to control (2 ml saline/ewe) or DEX-treated groups (im injections of 0.14 mg/kg ewe weight . 12 h) at 40-41 d gestation (dG). At 50, 100, 125, and 140 dG, fetal plasma and tissues were collected. DEX-exposed fetuses were lighter than controls at 100 dG (P < 0.05) but not at any other times. Fetal plasma ACTH levels and pituitary POMC and PC-1 mRNA levels were similar between groups. Fetal plasma cortisol levels were significantly reduced after DEX exposure in both male and female fetuses at 50 dG (P < 0.05), were similar at 100 and 125 dG, but were significantly higher than controls at 140 dG. At 140 dG, there was increased adrenal P450C(17) and 3beta-HSD mRNA in female fetuses and reduced expression of ACTH-R mRNA in males. Fetal hepatic CBG mRNA levels mimicked plasma cortisol patterns. DEX exposure reduced CBG only in males at 50 dG (P < 0.05). Placental mRNA levels of 11beta-HSD2 were increased after DEX in males (P < 0.05). Therefore, in sheep, early DEX may alter the developmental trajectory of the fetal hypothalamic-pituitary-adrenal axis, directly increasing fetal adrenal activation but not anterior pituitary function. In females, this effect may be attributed, in part, to increased fetal adrenal steroidogenic activity.

Effect of prenatal glucocorticoid treatment on size at birth among infants born at term gestation

OBJECTIVE

To determine whether prenatal treatment with a single course of glucocorticoids (GCs) affects size at birth among full-term infants independent of fetal size before GC administration or exposure to preterm labor (PTL).

STUDY DESIGN

In all, 105 full-term infants were recruited into three study groups (30 GC treated; 60 controls matched for gestational age (GA) at birth and sex; and 15 PTL controls without GC exposure). Size of the infants was estimated before treatment using two-dimensional (2D) ultrasound and by direct measurement at birth.

RESULTS

Length, weight and head circumference at birth were smaller among GC-treated infants compared with matched controls (P's<0.01), although fetal size did not differ before treatment (P's>0.2). Exposure to PTL did not account for this effect.

CONCLUSIONS

Prenatal treatment with a single course of GCs was associated with a reduction in size at birth among infants born at term gestation. This effect cannot be explained by differences in fetal size before treatment or exposure to PTL.

Should we be prescribing repeated courses of antenatal corticosteroids?

Single-course treatment with antenatal corticosteroids has been shown to enhance fetal maturation before preterm birth and to improve outcomes for the preterm infant. Based on this success, practitioners expanded use of the treatment to repeated courses of antenatal corticosteroids ahead of evidence demonstrating benefit and excluding harm. Experiments with animals and cohort studies have provided a body of evidence suggesting that repeated doses may further improve lung maturation but may be accompanied by deleterious effects on the developing brain and other organs. Randomised controlled trials of repeated treatments to date have provided mixed evidence but in general may indicate a small benefit in terms of postnatal lung function, but this is accompanied by restricted growth which may include the brain. In view of the well-established role that corticosteroids are known to play in brain development, and the marginal difference that repeated courses may make to outcome in the context of modern neonatal care, antenatal corticosteroid treatments should be restricted to single-course treatment.

Effects of prenatal dexamethasone treatment on postnatal physical, endocrine, and social development in the common marmoset monkey

The prophylactic treatment of diagnosed preterm delivery with synthetic glucocorticoids, such as dexamethasone (DEX), is commonplace. Long-term effects of such treatment are not well understood. In the present study, we exposed pregnant common marmosets (Callithrix jacchus), small-bodied monkeys that are therefore advantageous for long-term primate studies, to daily repeated DEX (5 mg/kg orally) either during early (d 42-48) or late (d 90-96) pregnancy (gestation period of 144 d). Relative to control, we investigated DEX effects in terms of maternal endocrinology (plasma cortisol and estrogen titers) and offspring physical growth, plasma and urinary ACTH and cortisol titers, and social and maintenance behaviors from birth to weaning. Both DEX treatments resulted in markedly reduced maternal plasma cortisol titers during treatment and reduced estimated gestation period. Both treatments were without effects on neonate morphometric measurements and basal hypothalamic-pituitary-adrenal axis activity. Early DEX treatment resulted in increased infant body weight at postnatal d 56 and 84, co-occurring at the behavioral level with increased time spent in eating solid food, a mobile state, solitary play, and exhibiting tail hair piloerection. The constellation of physical and behavioral effects of early DEX suggests interesting parallels with the human metabolic syndrome, providing primate support that the latter is causally associated with the fetal environment, including prenatal programming. This novel primate in vivo evidence for postnatal effects of prenatal synthetic glucocorticoid exposure indicates the importance of improved understanding of this acute clinical treatment in terms of its long-term effects on offspring well-being.

Prenatal dexamethasone exposure induces changes in nonhuman primate offspring cardiometabolic and hypothalamic-pituitary-adrenal axis function

Prenatal stress or glucocorticoid administration has persisting "programming" effects on offspring in rodents and other model species. Multiple doses of glucocorticoids are in widespread use in obstetric practice. To examine the clinical relevance of glucocorticoid programming, we gave 50, 120, or 200 microg/kg/d of dexamethasone (dex50, dex120, or dex200) orally from mid-term to a singleton-bearing nonhuman primate, Chlorocebus aethiops (African vervet). Dexamethasone dose-dependently reduced maternal cortisol levels without effecting maternal blood pressure, glucose, electrolytes, or weight gain. Birth weight was unaffected by any dexamethasone dose, although postnatal growth was attenuated after dex120 and dex200. At 8 months of age, dex120 and dex200 offspring showed impaired glucose tolerance and hyperinsulinemia, with reduced (approximately 25%) pancreatic beta cell number at 12 months. Dex120 and dex200 offspring had increased systolic and diastolic blood pressures at 12 months. Mild stress produced an exaggerated cortisol response in dex200 offspring, implying hypothalamic-pituitary-adrenal axis programming. The data are compatible with the extrapolation of the glucocorticoid programming hypothesis to primates and indicate that repeated glucocorticoid therapy and perhaps chronic stress in humans may have long-term effects.

[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.

Antenatal steroid therapy: have we undervalued the risks?

Antenatal corticosteroid therapy to enhance fetal lung maturation in pregnancies at risk for preterm delivery is used commonly, based on the assumption that its established benefits outweigh associated risks. Corticosteroid treatment does confer some risks, particularly with respect to restricted brain growth and disordered neuronal development. These alterations have the potential for long-term effects on health. They deserve further study, and should not be undervalued. Corticosteroid therapy should be applied selectively in those situations in which the risk of preterm birth is very high and the likelihood of severe respiratory distress syndrome substantial.

Effects of multiple courses of antenatal corticosteroids on blood-brain barrier permeability in the ovine fetus

OBJECTIVE

To test the hypothesis that multiple courses of antenatal corticosteroids accentuate the decreases in blood-brain barrier permeability observed after a single course of corticosteroids in preterm ovine fetuses.

METHODS

Chronically instrumented 106-day gestation ovine fetuses were studied after single and multiple courses of dexamethasone or placebo were given to ewes beginning at 104 to 106 or 76 to 78 days of gestation, respectively. In the single-course groups, the ewes received dexamethasone (6 mg, n = 6) or placebo (n = 6) as four intramuscular injections every 12 hours over 48 hours. In the multiple course groups, the ewes received the same treatment (dexamethasone, n = 9, or placebo, n = 8), once per week for 5 weeks starting at 76 to 78 days of gestation. Blood-brain barrier permeability was quantified with the blood-to-brain transfer constant (K(i)) for alpha-aminoisobutyric acid (AIB) in the brain regions of the fetuses 12 hours after the last injection of dexamethasone was given to the ewes at 106 to 107 days of gestation.

RESULTS

Both single (analysis of variance [ANOVA]; main effects for dexamethasone treatment, F = 5.92, P <.04) and multiple (ANOVA; main effects for dexamethasone treatment, F = 4.74, P <.04) courses of antenatal corticosteroids were associated with decreases in blood-brain barrier permeability in the brain regions of the ovine fetus. However, the multiple courses did not accentuate (ANOVA; main effects for single versus multiple courses, F = 1.06, P = .32) the decreases in permeability observed after a single course.

CONCLUSION

Contrary to our hypothesis, antenatal treatment with a 5-week course of corticosteroids did not accentuate the reductions in blood-brain barrier permeability that we observed after a single course of corticosteroids in the fetus.

Endocrine regulation of human fetal growth: the role of the mother, placenta, and fetus

The environment in which the fetus develops is critical for its survival and long-term health. The regulation of normal human fetal growth involves many multidirectional interactions between the mother, placenta, and fetus. The mother supplies nutrients and oxygen to the fetus via the placenta. The fetus influences the provision of maternal nutrients via the placental production of hormones that regulate maternal metabolism. The placenta is the site of exchange between mother and fetus and regulates fetal growth via the production and metabolism of growth-regulating hormones such as IGFs and glucocorticoids. Adequate trophoblast invasion in early pregnancy and increased uteroplacental blood flow ensure sufficient growth of the uterus, placenta, and fetus. The placenta may respond to fetal endocrine signals to increase transport of maternal nutrients by growth of the placenta, by activation of transport systems, and by production of placental hormones to influence maternal physiology and even behavior. There are consequences of poor fetal growth both in the short term and long term, in the form of increased mortality and morbidity. Endocrine regulation of fetal growth involves interactions between the mother, placenta, and fetus, and these effects may program long-term physiology.

Histochemical analyses of altered fetal lung development following single vs multiple courses of antenatal steroids

A single course of antenatal steroids is widely used during preterm labor to promote fetal lung maturation. However, little is known regarding efficacy and safety of multiple courses of antenatal steroids. In animal models and clinical trials, treatment with glucocorticoids can inhibit growth. The present study of single- vs multiple-course steroids in pregnant ewes analyzes the effects of steroids vs placebo on fetal lung histopathology. Single-course groups received dexamethasone (Dex) 6 mg or normal saline every 12 hr for 48 hr at 104-106 days of gestation (term = 150 days). Multiple-course groups received the first course at 76-78 days; this was repeated weekly for 5 weeks. At 108 days, lungs were analyzed using immunohistochemistry for alpha-smooth muscle actin, a myofibroblast marker and proliferating cell nuclear antigen. Cell injury/death was evaluated using TdT-mediated dUTP digoxigenin nick end labeling (TUNEL) analysis. Although fetal growth was restricted by either single or multiple courses of Dex, alveolar development was accelerated as measured by mean linear intercepts. Alveolar walls were thinner, developing septa were longer, and septal myofibroblasts were increased for both Dex groups compared with controls. Cell proliferation increased following multiple steroid courses, especially in the distal parenchyma, with a corresponding decrease in apoptosis. These observations suggest that Dex promotes alveolarization, whether given in single or multiple courses.

Prenatal corticosteroid impact on hippocampus: implications for postnatal outcomes

Prenatal administration of corticosteroids is common in obstetrics to improve the outcome of premature deliveries. Many pregnant women receive multiple corticosteroid courses. Long-term follow-up studies in humans are limited, but those available suggest detrimental effects on the behavior of those children. Animal data also show adverse effects of prenatal corticosteroids mainly in the hippocampus, a structure sensitive to corticosteroid action. Several molecules involved in neuronal survival, seizure susceptibility, and behavior have been identified as possible targets of prenatal corticosteroid effects. These molecules include hippocampal glucocorticoid receptors, brain-derived neurotrophic factor, corticotropin-releasing hormone, and neuropeptide Y. Prenatal corticosteroid treatment permanently reprograms expression of these molecules. The future goals of research in this area include development of specific antagonists of corticosteroid activation pathways that would help differentiate between positive main effects and undesired adverse effects of prenatally administered corticosteroids.

Developmental consequences of antenatal dexamethasone treatment in nonhuman primates

Research assessing fetal exposure to dexamethasone and betamethasone in animals has raised concerns about the potential for adverse side effects following antenatal treatments, not withstanding the beneficial and desired improvement in lung function. Some of the inhibitory effects on physical growth and the long-term alterations in endocrine, immune and neural physiology may reflect species differences in the fetal sensitivity of rodents and monkeys to corticosteroids or perhaps could be attributed to the higher drug doses often used in animal studies. However, since steroidal drugs can be administered for extended periods in clinical practice, and also are occasionally given in the range found to cause significant effects on the brain and immune responses of infant monkeys, the simian studies have important cautionary implications for obstetrical and pediatric practice.

Perinatal corticosteroids: A review of research. Part I: Antenatal administration

The premature infant may receive therapeutic glucocorticoid drugs while in utero or in the postnatal period. This article (part I of a two-part series) discusses the benefits and risks of in utero, or antenatal, corticosteroids (ACS) for the premature infant. Part II addresses the benefits and risks of postnatal corticosteroid (PCS) use. There are numerous clinical studies on the therapeutic use of these steroids for the prevention of respiratory distress syndrome and chronic lung disease in the premature infant, although research results on the efficacy of repeated steroid exposure among premature infants vary. Premature infants who are exposed to repeated courses of ACS and/or high-cumulative-dose PCS may show no neurologic side effects until later in life. Research in newborn animal models focused on the timing, duration, and amounts of ACS and PCS. Current clinical research includes examination of the neurodevelopment of infants who are therapeutically exposed to perinatal corticosteroids, to identify safer minimal dose protocols. Over the past 30 years, corticosteroids have been increasingly prescribed before and after birth. Understanding the potential treatment benefits and risks to human fetuses and neonates is vital to clinical practice. This review presents historic and pharmacokinetic information about prenatal use of corticosteroids. It also offers scientific evidence of the benefits and risks identified in animal models and clinical trials, to stimulate thought that gtiides neonatal clinical practice.

Effects of three courses of maternally administered dexamethasone at 0.7, 0.75, and 0.8 of gestation on prenatal and postnatal growth in sheep

OBJECTIVES

To evaluate the effects of repeated low doses of maternally administered dexamethasone (DM) on growth in sheep during fetal life and the first 2 years of postnatal life.

METHODS

Ewes received 3 courses of DM (1 course: four 2-mg intramuscular injections at 12-hour intervals) or saline beginning at 103, 110, and 117 days of gestation (dGA). At 119 dGA, fetal BW and organ weight were recorded. Total placentome number, weight, and morphologic distributions were recorded. Placentome glucocorticoid receptor expression was determined by immunocytochemistry. Newborn BW and organ weight were recorded within 12 hours of birth. Duration of gestation was recorded. Measurements were collected on body weight (BW), biparietal diameter (BPD), crown-to-rump length, thoracic girth circumference, abdominal girth circumference, and radial bone length for 2 months. Maternal estradiol and progesterone levels were measured daily from 135 dGA.

RESULTS

At 119 dGA, DM significantly decreased BW. Placentome glucocorticoid receptor expression increased after DM exposure. DM did not significantly decrease BW at birth but did prolong gestation length. DM decreased maternal estradiol before lambing. DM decreased newborn brain weight and BPD. After 2 weeks of age, no effect of DM on postnatal growth could be found.

CONCLUSIONS

This study shows that repeated maternal DM treatment at doses threefold lower than what women in preterm labor receive results in decreased fetal BW, prolonged gestation length, decreased newborn brain weight, and BPD.

Antenatal factors and the development of bronchopulmonary dysplasia

The lung of the preterm fetus is often exposed to antenatal glucocorticoids, and histologic chorioamnionitis is frequent. Clinically and experimentally, antenatal glucocorticoids and/or chorioamnionitis are associated with early lung maturation, but in experimental models, both glucocorticoids and intra-uterine inflammation decrease alveolarization. Experimental chorioamnionitis also can amplify the inflammatory response of the preterm lung to mechanical ventilation. In this article, the hypothesis developed is that bronchopulmonary dysplasia occurs because of repetitive adverse lung exposures, or hits, and that the initial hits may be antenatal glucocorticoid exposure and/or antenatal inflammation.

Controversies in the use of antenatal steroids for fetal maturation

After decades of caution and reticence, by the early 1990s, the use of antenatal corticosteroids was accepted as a pharmacologic intervention to reduce neonatal morbidity and mortality associated with prematurity. Many prospective studies yielded robust evidence to support the use of corticosteroids for fetal maturation. Their use is no longer disputed. Nevertheless, many unanswered questions remain regarding issues such as the ideal dose, drug form, regimen, or timing of treatment. This article explores many of the unanswered questions associated with antenatal corticosteroid use.