Maternal hyperoxygenation as the way to treat aortic arch dimensions in fetuses with coarctation

iStock_000001495171_LargeAortic coarctation (CoA) constitutes 6-8% of all live births with hearth diseases. It can occur in various stages: from a discrete constriction of the aortic isthmus to the hypoplasia of the aortic arch. Prenatal diagnosis of CoA may result in lower mortality rate and better haemodynamic parameters (due to the early operation of CoA) by sustaining the patency of the aorta (1). The way to treat the fetus with CoA could be sustained, intermittent maternal hyperoxygenation (HO). Scientists discovered that HO can indicate the increase of left cardiac dimensions and the aortic isthmus (in fetuses with isolated CoA). Effects are mostly noticed in 4th week of treatment. The duration of the HO should dependent on left heart dimensions

Maternal hyperoxygenation was applied in various illnesses (e.g. intrauterine growth retardation(2,3), pulmonary hypoplasia (4), and congenital diaphragmatic hernia (5). Some information that HO increased fetal pulmonary venous return (6) and improved hypoplastic cardiovascular dimensions (7) can be found.

Doctors from The Second Xiangya Hospital of Central South University in China (8) have already hypothesized that HO can increase the left cardiac dimensions and aortic isthmus in fetuses with CoA. They conduct a prospective study. The cases population consisted of pregnant women referred for fetal echocardiography because of CoA. Fetuses with another heart diseases (e.g. aortic atresia, ventricular septal defect) and mothers with illnesses (e.g. preeclampsia, gestational diabetes, hypothyroidism) were excluded from the research. Experiment continued from January 2012 to December 2015. The study consists of 96 fetuses: 48 healthy fetuses as a control group, and 48 fetuses with CoA. Hyperoxygenation was applied to 24 fetuses with CoA. 45% oxygen was administered (6l/min) to the mother using a face mask in the mode of 3 hours per morning and 3 hours per afternoon. Other 24 fetuses with CoA got placebo (air). Materno – fetal HO started in 30.44 ± 2.89 hbd and ended at gestational age 39.68 ± 0.78 weeks. No baby was found to have an abnormal ocular fundus upon examination, and no mother had an abnormal chest X-ray.

As for the case group with oxygen, the left heart dimension Z-scores (mitral valve, aortic valve, and ascending aorta), and aortic isthmus increased gradually (p<0.01), especially after 4 weeks of therapy and neared to the norm at the end of the study. Additionally 20.8% fetuses had abnormal flow at the end of oxygen therapy - the left heart dimensions were unchanged (p<0.01). In the group with air doctors observed no changes after 8 weeks of study (p>0.05). In this group left heart dimensions were lower than in control group. In the case group with positive response for the HO, amendments had been observed during 4 weeks of HO (p<0.01). During 8 weeks increasing trend could be observed, but it was non-statistically significant (p>0.05). Right cardiac dimensions stayed unchanged (p>0.05).

To conclude sustained, intermittent maternal hyperoxygenation can be safely used to improve left heart dimensions in fetuses with isolated coarctation. Although HO was administered in some other studies (e.g. left cardiac hypoplasia), more research seem to be needed to validate foregoing findings.

Written by: Sebastian Sawonik

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8. Zeng, S. et al. Sustained maternal hyperoxygenation improves aortic arch dimensions in fetuses with coarctation. Sci. Rep. 6, 39304; doi: 10.1038/srep39304 (2016).

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