DISCUSSION
In this present study, significantly higher values of the pulmonary
artery acceleration to ejection time (PATET) were found in the fetuses
whose mothers were complicated by IHCP. Notwithstanding detection of
frequent NICU admission and respiratory distress in the IHCP group,
these were not correlated with PATET. Gestational age at birth and APGAR
score at fifth minutes were the most important determinants of the NICU
admission and respiratory complications.
In literature, although many studies that were focused on the
relationship between PATET and respiratory complications, conflicting
results have been reported. Pulmonary artery acceleration time and right
ventricle ejection time were first assessed by Kitabatake et al, and
they reported that decreased values of both measurements have been found
in pulmonary arterial hypertension 12. Fuke et al,
showed that AT/ET ratio of the branches of pulmonary artery appeared to
be an accurate parameter with which to predict pulmonary hypoplasia13. To date, the PATET has been investigated to
predict RDS especially premature fetuses 10-14. Few
studies that were focused on PATET values of late term and term fetuses
showed that inverse correlation between fetal PATET value and transient
tachypnea of newborns 8,15.
However, in 2010, Azpurua et al, reported that the At/Et in the main
pulmonary artery waveform correlated inversely with the
lecithin/sphingomyeline ratio 11. In 2013, Kim et al,
demonstrated that an elevated At/Et ratio in the fetal pulmonary artery
was associated with RDS as supporting Azpurua 10. The
other studies that were referred above, showed contrast findings from
Azpurua’s study and this study. The findings of both studies
observations are similar to our study results in terms of the
relationship between elevated PATET and lung immaturity. Possible
explanation of it, fetal lung surfactant production is lower in IHCP
than healthy fetuses and possible lung damage has been with elevated
PATET.
The immunological response to tissue injury or microbial invasion
involves pro inflammatory and anti-inflammatory responses in human
fetuses. It has been showed that the newborns exposed to systemic
inflammation in utero were with higher frequency of neonatal morbidity
as a result of fetal inflammatory response syndrome that is associated
with multi systemic involvement 16. Fetal lung
inflammation is characterized by expression of many different cytokines
and the effect of inflammation results as stimulated surfactant
production. In literature, there are studies investigating inflammatory
process intended for clarifying the etiology of IHCP and the
pathophysiological pathways of bile acid induced inflammation affecting
fetal and neonatal outcomes 17-19. Herraez et al,
reported that accumulation of maternal bile-acids triggered an
inflammatory response in maternal and fetal lungs and the importance of
released macrophage associated phospholipase A2 in RDS development5.
Previous studies demonstrated that the RDS rate was approximately three
times higher among the newborns whose mothers were complicated by IHCP20,21. Arthuis et al, also found significant
difference for intensive care unit admission rates and they reported
that higher biliary acid levels were in this group 20.
NICU admission rate was found higher in our study group which is
consistent with the previous studies. Although, respiratory distress
rate (5/18) was higher in our study group, it couldn’t be found
statistically significant when compare to the control group (3/37). That
may be explained as all NICU admissions in the control group due to
respiratory distress and lower ratio of respiratory distress in all NICU
admission for the study group.
To the best of our knowledge, this is the first study that evaluates
PATET in fetuses whose mothers were complicated by IHCP. The strength of
this study was its prospective and well-designed and being the first
study in IHCP as mentioned above. On the contrary, the main limitation
was the small sample size depending on the lower incidence of IHCP and
couldn’t have been categorized based on severity of the disease.
Additionally, the secondary hypothesis of this study couldn’t be
documented with these results.
In conclusion, higher values of the main pulmonary artery acceleration
to ejection time that were detected in fetuses whose mothers were
complicated by IHCP may be helpful to understand fetal lung damage
secondary to IHCP. Larger prospective studies or evaluation of branches
PATET values may be enlighten the prediction of respiratory
complications of these newborns.