Assessment of gestational age plays a pivotal role in determining the level of care required by a preterm neonate, its subsequent growth, development, and survival.(18) While methods utilized for gestational age assessment include ultrasound investigations,(19) LMP,(20) 21-item Dubowitz, (21) 12-item Ballard,(22, 23) the 6-item Capurro,(24) and the 6-item Eregie, (25) only the former two are considered to be the gold standard. However, owing to certain impediments, such as poverty and subsequent scarcity of resources, access to ultrasound investigations is hindered.(13) Moreover, maternal illiteracy—with the resultant lack of antenatal care and poor documentation of LMP—poses significant challenges in the determination of gestational age.(20) Consequently, the failure to detect preterm pregnancy results in delay in interventions that could prevent neonatal morbidity and mortality.(26)
The NBS system, which is the current standard for GA assessment in developing countries, has a physical and neurological criterion. Despite the accuracy of this assessment, certain limitations reduce its efficacy in low-middle income countries (LMICs). These include the requirement of pediatric-trained personnel, as well as variations in assessments conducted by different individuals. In contrast, anthropometric measurements collected by health workers are more reliable, since they are easier to perform and are free of observer bias.(27)
Among our principal findings, we observed a significant linear relationship between head circumference, CHL and GA. Within this analysis, the correlation of HC + CHL with GA was determined as the most significant. Additionally, our analysis guided the preparation of an equation to determine gestational age through anthropometric measurements of head circumference, crown-heel length, or a combination of both.(28)
Gestational Age And Anthropometric Values:
In our study, the mean head circumference at 25w, 26w, and 27w, was 22·5 ± 0·5cm 23·7 ± 1·8cm and 24·6 ± 1·1cm respectively, for both genders. These results demonstrated considerable similarity to a study conducted in the US, wherein, the mean percentile for head circumference at the aforementioned gestational ages, were 22·7cm, 23·6cm, 24·5cm and 23·2cm, 24·2 cm, 25·2cm respectively, for both males and females.(29) Our results for head circumference were also corroborated by a study conducted in Turkey, which demonstrated a mean head circumferences, very similar to our own; for neonates at 34w, 35w, 36w of gestation.(30) A study conducted by Das et al in India however, demonstrated the mean percentile of head circumferences to be 24·1cm, 24·6cm and 24·7cm at 28w, 29w and 30w. These results were found to be contrary to the mean percentile of our population (25·5cm 27·5cm 29·0cm).(27)
With regards to CHL, a multi-center cross-sectional study conducted across 248 hospitals in the US revealed measurements of mean percentile of head circumference and crown heel length that were like our study. The mean crown heel length at 25w, 26 w, and 27w in the aforementioned study were 32·3cm, 33·6cm, and 35·0cm for females and 32·9cm, 34·3cm, and 35·7cm for males respectively.(29) In our study, the mean crown heel length for 25w, 26w, and 27w were 33·5 ± 0·0cm, 33·6 ± 1·5cm,, and 35·5 ± 1·3cm for both genders.
These results were corroborated by the aforementioned study conducted in Turkey which, at 34w, 35w, 36w, reported a mean percentile for crown heel length of 44·9cm, 46·5cm, 47·8cm, and 45·5cm, 46·0cm, and 47·3cm for males and females respectively.(30) In our study, the mean CHL for the aforementioned GAs were 45·3 ± 1·6cm, 46 ± 0·0cm, and 46·8 ± 3·3cm respectively.
Similar to HC, Das et al reported a mean crown heel length which differed from the findings observed in our population (37·6 ± 2·5cm 39·3 ± 1·6cm, and 41·5 ± 2·2cm at 28w 29w and 30w respectively). (27)
The disparity observed between the percentiles in our study, in contrast to studies conducted across the world, could be attributed to varying economic backgrounds, differences in sample size, ethnicity and demographic profile.
Correlation Between Anthropometric Values And Ga
On analysis, our results corroborated the findings of a study conducted within a Western Indian population, which demonstrated a strong correlation between GA and HC (r = 0·977).(31) Similarly, Das et al demonstrated a strong correlation (r = 0·863) between HC and GA of 28 and 41 weeks within an Eastern Indian neonate population.(27) In contrast, a cross-sectional study conducted at the neonatology division of a tertiary hospital in Delhi, India observed a moderate correlation between gestational age and the head circumference (r = 0·52), through which a linear regression equation of GA = 19·73+(0·504×HC) was generated.(32) With regards to the strength of association between GA and CHL, our results were in line with the findings of Thawani et al, who observed a moderate association between CHL and GA (r = 0·56).(32)
Contrasting our findings, however, a study conducted in northeast Ethiopia by Tiruneh et al, demonstrated a weak correlation, when assessing both HC and CHL for GA assessment (r = 0.14 and r = 0.115 respectively). These differences might be explained by significant variations in their study population.(33)
Our study brings to light the existing discrepancies in access to resources between high income countries (HIC) and LMICs. Despite extensive efforts to establish stepping stones to health equity—such as the development of Millennium Developmental goals (34) and Sustainable developmental goals (4) by the UN, LMICs lag far behind.(3) This disparity was further exacerbated by the onset of the recent COVID-19 pandemic. (35)
Certain measures can serve to alleviate the problem at hand. One of which is access to basic technology such as ultrasound investigations in a subsidized amount or free of cost, so as to make the resource available to a larger majority. This will, in turn, promote maternal health and antenatal care for infants. Additionally, determining an inexpensive and universal alternative to an ultrasound could serve as an effective measure. Moreover, the work of social workers and medical professionals is more crucial than ever. This includes proper counselling of women regarding the record keeping of LMPs, highlighting the importance of a balanced diet for the mother as well as the infant, and the risks associated with a medically unsupervised pregnancy.
Strengths And Limitations:
While our results have important implications, certain limitations were encountered. This was a single center study, and larger multi-center studies are essential in determining equations for different demographic areas, with precision.