This prospective study was conducted at Apollo BGS Hospital, Mysore from December, 2017 to November, 2018, after clearance from institutional ethics committee. After informed parental consent, babies of 35 to 41 weeks gestation were included in this study. Babies with congenital anomalies and babies who were discharged within two days of birth were excluded. Pre-pregnancy weight of mother was obtained from antenatal card. Mother’s weight at the time of delivery was recorded using standard electronic weighing machine, and weight gain during pregnancy was calculated. Gestational age was calculated from last menstrual date, if not known, dating scan during first trimester or modified New Ballard scoring of neonates was used to ascertain gestational age. Birthweight was measured using a calibrated electronic weighing machine, and length was measured with an infantometer using standard methodology [9].

Intergrowth-21 charts were used to plot anthropometric details of the baby [10]. Ultrasound examination was done for all the enrolled babies on day 3 of life to measure aortic intima-media thickness. All the ultrasound scans were carried out by a single radiologist who was blinded to birthweight and weight group of the baby. High resolution B mode measurement was performed using linear high-resolution probe of 10-12 MHz at L1-L2 i.e. supra renal aorta using Philips HD 11xe ultrasound system (Koninklijke Philips NV). Intima-media thickness was defined as distance from the leading edge of first echogenic line to the second line. The first line represents lumen-intima interface, and second line represents collagen containing upper layer of the adventitia. The image was focused on the dorsal wall of the aorta, and a gain setting was used to optimize image quality.

Statistical analyses: All the data were entered in a Microsoft excel sheet and analyzed using SPSS 22.0. Pearson correlation coefficient was calculated for continuous variables and ANOVA was used to compare aIMT across different birthweight categories. All the tests of significance were carried out at 5% level of significance.

A total of 200 (94 females) babies were enrolled in the study. Mean (SD) pre-pregnancy weight of the mothers was 55.32 (7.05) kg, mean (SD) height was 158 (4.67) cm and mean (SD) weight gain during pregnancy was 14.12 (2.62) kg. The mean (SD) birth weight of enrolled babies was 2.79 (0.60) kg, mean (SD) length was 48.75 (2.76) cm and mean (SD) head circumference was 33.03 (1.47) cm.

The mean (SD) aIMT observed in our study was 0.43 (0.15) mm. aIMT showed a negative correlation with birthweight and length of the baby with correlation coefficient (r) of –0.64 and –0.61 (Fig. 1). However, there was a poor correlation of aIMT with gestational age (r= –0.31), maternal weight (r= –0.03), maternal height (r = –0.12) and weight gain during pregnancy (r= –0.29). There was no significant difference in mean (SD) aIMT in male and female babies [0.45 (0.16) and 0.43 (0.14)].

Fig. 1 Scatter diagram of correlation of aortic intima-media thickness (aIMT)

Value of aIMT was significantly more in SGA babies than their AGA counterparts (Table I). For every given gestation, SGA babies had significantly higher aIMT than AGA babies (Table II).

Table I Aortic Intima-Media Thickness in Different Birthweight Groups (N=200)

Table II Aortic Intima-Media Thickness among Infants With Different Gestational Age (N=200)

In this study, we enrolled 200 healthy neonates of 35-41 weeks of gestation and aIMT was measured on dorsal wall of aorta between L1-L2, and this was correlated with birth weight. aIMT was higher in babies with lower birth weight irrespective of gestational age. Similar correlation was found between length and aIMT. SGA babies in our study had significantly higher aIMT than their AGA counterparts. Mean aIMT value was fairly static across gestation age of 35-41 weeks within SGA and AGA categories.

We had a relatively large sample size, and all the aIMT measurements were done by a single radiologist blinded to birthweight cohort, hence eliminating the possibility of any inter observer variation. However, we did not look into risk factors for SGA and possible differential effect of these risk factors on aIMT.

Our value of mean aIMT of 0.44 mm is comparable to the data reported from India [11,12]. AGA babies in our study had a mean aIMT of 0.36 mm which is lower compared to most of other reported values, and SGA babies had a mean aIMT of 0.64 mm which is higher than most other values reported from the Western population [1,6,7]. This difference could be either due to racial variation, or due to different nutritional and medical illness profile in Indian mothers.

Even though, aIMT has been investigated in newborn period, the natural history of these lesions and possible reversibility of these lesions has never been evaluated. Long term follow up of these babies for confirming evolution of these lesions into atherosclerotic plaques is needed.

Ethical clearance: Institutional ethics committee, Apollo BGS hospital; No. 11/2018. April 21, 2018.

Contributors: RD, VV, GG: formulated the study, drafted the protocol and involved in final writing of the article; RD, GG: collected and analyzed the data; VV: did the sonographic measurement of all cases.

Funding: None; Competing interest: None stated.

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