Effect of antenatal corticosteroid treatment on the fetal lung: a magnetic resonance imaging study

Comparison of fetal lung maturation in fetuses with intrauterine growth restriction with control group, using lung volume, lung/liver and lung/muscle signal intensity and apparent diffusion coefficient ratios on different magnetic resonance imaging sequences

PURPOSE

To compare lung volume, lung apparent diffusion coefficient (ADC) and signal intensity ratio (SIR) on different magnetic resonance imaging (MRI) sequences between intrauterine growth restriction (IUGR) fetuses and the control group.

MATERIALS AND METHODS

49 IUGR and 58 non-IUGR fetuses were imaged using 3 Tesla MRI units. Total lung volume (TLV), lung/liver SIR (LLSIR) and lung/muscle SIR (LMSIR) in T1 and T2-weighted sequences and lung/liver ADC ratio (LLADCR) and lung/muscle ADC ratio (LMADCR) were assessed.

RESULTS

LLSIR and LMSIR were significantly higher in the T1-weighted sequence (p-value: .03) and LLADCR and LMADCR were significantly lower on diffusion-weighted imaging (DWI) in IUGR fetuses compared to the control group (p-value: .01). There was no significant difference in SIRs in the T2-weighted sequence between the two groups. Although TLV was increased with gestational age in both groups, it was significantly lower in the IUGR group (mean: 82 ± 22.7 ml vs. 110.8 ± 18 ml, p-value: <.001).

CONCLUSION

The T1-weighted sequence and DWI seem to be better than the T2-weighted sequence for assessing the faint difference of lung maturity between groups. However, SIR differences were not as meaningful as TLV differences and this could be related to the complex maturation process in IUGR fetuses as the effect of higher endogenous corticosteroids.

Determination of fetal lung maturity using magnetic resonance imaging signal intensity measurements

PURPOSE

The objective of this study was to determine if magnetic resonance signal intensity measurements can be used to predict gestational age and hence fetal lung maturity.

METHODS

This institutional review board-approved study was a retrospective review of 394 fetal magnetic resonance imaging cases from a single institution for the years 2001 to 2011. For each case, T1- and T2-weighted sequences were selected for data collection. A single reviewer obtained 10 regions of interest (when possible) from each scan (fetal lung, fetal liver, fetal muscle, fetal spleen, and maternal urine, for both T1- and T2-weighted sequences). The medical record was searched for relevant information including best estimate of gestational age, Apgar scores, karyotype, and fetal diagnosis. A variety of organ-to-organ ratios and direct organ signal intensity measurements were assessed for correlation with gestational age.

RESULTS

Three hundred thirty-five cases met inclusion criteria with gestational ages ranging from 17 to 39 weeks (mean, 28.6 weeks). A significant relationship between magnetic resonance signal intensity ratios and gestational age was demonstrated on the T2 lung-to-liver, T2 lung-to-spleen, T2 lung-to-muscle, T1 lung-to-liver, and T1 lung-to-spleen ratios (P < 0.05). T2 lung-to-liver and T2 lung-to-muscle demonstrated the strongest relationship with gestational age (best correlation r = 0.483, P < 0.001). T1 lung-to-liver and T1 lung-to-spleen demonstrated inverse relationships with gestational age (r = -0.174 [P = 0.03] and r = -0.236 [P = 0.02], respectively).

CONCLUSIONS

A significant correlation between multiple signal intensity ratios and gestational age is demonstrated. However, the large variances preclude a clinically useful relationship.

Programming of respiratory health in childhood: influence of outdoor air pollution

PURPOSE OF REVIEW

This overview highlights recent experimental and epidemiological evidence for the programming effects of outdoor air pollution exposures during early development on lung function and chronic respiratory disorders, such as asthma and related allergic disorders.

RECENT FINDINGS

Air pollutants may impact anatomy and/or physiological functioning of the lung and interrelated systems. Programming effects may result from pollutant-induced shifts in a number of molecular, cellular, and physiological states and their interacting systems. Specific key regulatory systems susceptible to programming may influence lung development and vulnerability to respiratory diseases, including both central and peripheral components of neuroendocrine pathways and autonomic nervous system (ANS) functioning which, in turn, influence the immune system. Starting in utero, environmental factors, including air pollutants, may permanently organize these systems toward trajectories of enhanced pediatric (e.g., asthma, allergy) as well as adult disease risk (e.g., chronic obstructive pulmonary disease). Evidence supports a central role of oxidative stress in the toxic effects of air pollution. Additional research suggests xenobiotic metabolism and subcellular components, such as mitochondria are targets of ambient air pollution and play a role in asthma and allergy programming. Mechanisms operating at the level of the placenta are being elucidated. Epigenetic mechanisms may be at the roots of adaptive developmental programming.

SUMMARY

Optimal coordinated functioning of many complex processes and their networks of interaction are necessary for normal lung development and the maintenance of respiratory health. Outdoor air pollution may play an important role in early programming of respiratory health and is potentially amenable to intervention.

Maternal smoking and fetal lung signals--an in utero MRI investigation

OBJECTIVE

To investigate whether fetal lung signals and fetal lung signal progression over gestation observed on magnetic resonance imaging are different in mothers who reported smoking during pregnancy compared with nonsmoking controls.

METHOD

Cross-sectional retrospective study of 100 consecutive singleton pregnancies that underwent magnetic resonance imaging. Fetal lung-liver signal intensity ratios of 18 fetuses of mothers who reported smoking during pregnancy were compared with 82 fetuses of nonsmoking controls.

RESULTS

Average gestational age at magnetic resonance imaging was 26.4 ± 5.2 weeks (Range 18.4-38.2 weeks). Cases reported smoking between 2 and 15 cigarettes per day. The mean number of cigarettes per day for cases was 9.2 ± 3.4. Mean fetal lung-liver signal intensity ratios did not differ significantly between the two groups (p = 0.8). They showed a linear increase with gestational age (r(2) = 0.3). Multiple regression analysis of lung-liver signal intensity ratios using gestational age and smoking status as predictors revealed a significant influence of gestational age (p < 0.0001) but not maternal smoking status (p = 0.8) on fetal lung-liver signal intensity ratios.

CONCLUSIONS

Fetuses of mothers who reported smoking during pregnancy show similar lung signals and lung signal progression over gestation on magnetic resonance imaging as nonsmoking controls.