Introduction
The first major organ system to function is cardiovascular system as there is need to transport gases to fetal cells. 1 Aorta is the largest elastic artery in human body, the anatomy and role of aorta in prenatal life differ from those in postnatal life. The circulation of blood differs between the fetal and postnatal life. These differences involve the changing pressure load of the proximal aorta. In prenatal life, the ascending aorta and the aortic arch carry half of the blood volume that flows through the thoracic aorta. The intial segment of the aorta also carries less blood in the prenatal period than in postpartum period.2 One of the common congenital defects in neonates is the structural defects of heart and great blood vessels accounting for 8 in 1,000 live births.3
Measurements of great vessels determines the function of gestational age.4 To have knowledge about the normal diameter of aorta is vital for clinicians as they will be able to predict when the development of aneurysm of aorta occurs.5 Prior knowledge of anatomical variation of aorta is essential for interventional radiologists before diagnostic and therapeutic imaging procedures to successfully accomplish the procedure.6 It is established that there is association of thicker aorta with infants who had intra uterine growth restriction, which suggests that there is association of prenatal events and structural changes in aorta. Therefore, abdominal aortic intima – media thickness measurement is vital for determining atherosclerosis risk in children. 7
Hence measurement of the diameter and length of aorta at different gestational age serves numerous purposes. There is no existing information about the histology of fetal aorta documented and is important to know the changes from fetal to adult. Hence the present study was conducted.
Materials and Methods
The study was performed at Sapthagiri Institute of Medical Sciences and Research center, Bangalore from December 2012 to December 2015.The study was conducted in 16 spontaneously aborted fetus ranged from 10th week upto term, irrespective of sex, whose gestational age were determined from LMP. All fetuses were preserved in formaldehyde solution for 3 months period. The Crown Rump Length, length and the external diameter of the ascending aorta, arch of aorta and descending aorta was measured. The diameter measurements & histological sections were taken in the following locations: the diameter of the ascending aorta was taken at the level of aortic valve, the arch of aorta taken between left common carotid artery and left subclavian artery and the decending aorta beneath the arterial duct. Measurements were taken twice and then averaged so as to minimize bias errors. Values were also compared with previous studies for their statistical significance.
Statistical analysis was performed using the SPSS 17 Software package. Data is presented as mean and standard deviation. Sections of aorta were stained with H and E and were studied.
Results
The analyzed results are shown below.
Table 1
Aortic Measurements
|
Parameter |
|
Ascending aorta |
Arch of aorta |
Descending aorta |
|
Length |
r(p) |
0.374(<0.05) |
0.417(<0.05) |
0.617(<0.001) |
|
Diameter |
r(p) |
0.54(<0.001) |
0.65(<0.000) |
0.68(<0.000) |
Table 2
Correlation between crl and different parts of aorta
Discussion
According to Yahel et al8 the abdominal aorta length constituted about 32.4% - 43.2% of the descending aorta length and in present study positive correlation was seen between the stature and the aortic length irrespective of gestational age.
Ozguner and sulak1 reported that values of aortic length has a proportionate evolution with gestational age. The present study revealed -proportionate growth of the aortic segments as per the crown rump length.
M.spinda’s9 study revealed that the length of ascending aorta, arch of aorta and abdominal aorta were in ratio of 5:7:22 and showed no change throughout gestational age.9 Similar findings were obtained in present study.
Dariusz nowak’s10 showed that proximal ascending aorta is broader than the proximal thoracic aorta and concluded that aorta growth is linear in vessel segments. Similar results were obtained in our study.
Conclusions
As the gestational age increases the aortic parameters increase according to CRL of fetus.
The ratio of the aortic parameters however remains the same irrespective of the gestational age.
Irrespective of gestational age, there is a significant correlation between the CRL and aortic parameters, especially with descending aorta.
The histological study of the various segments of fetus of different gestational age revealed that it is similar to adult aorta.
