Background: Neonatal mortality in preterm live births is high. Therefore, knowledge of the gestational age (GA) at birth is crucial for the management and predicting prognosis of a newborn. Common methods for estimating GA such as the last menstrual period, ultrasonography, and post-natal Ballard scoring have some limitations. This study aimed to determine the relationship between foot length and GA and to develop a regression equation for predicting GA of the neonates born in Pakistan.
Methods: Data for this analysis were extracted from the hospital files of eligible women by trained study midwives. Midwives were also trained in performing the Ballard examination and taking foot length using a disposable measuring tape within an hour of the birth. The measurement was taken from the mid-point of the heel to the end of the longest toe. The GA was calculated using an android-based GA calculator, which used a report of last menstrual period, ultrasound examination, and Ballard examination. The data were analyzed using SPSS version 19. Scatter plots were constructed to assess the linearity and co-efficient of determination and the correlation was calculated. Simple and Multiple Linear regression was used to construct predicting equations for GA.
Results: Both foot length and GA were available for 1542 cases and were analyzed. The median GA was 34.5 weeks with an interquartile range (IQR 4.7) and the median foot length was 7 cm (IQR 1.4). There was a positive linear relationship between foot length and GA (r2 81.7%, p-value <0.001). Stratified analysis showed an r2 of 81.7% for males and 81.6% for females. The r2 for stillbirths was 84.1% and, 82.3% for live births. The r2 for macerated stillbirths was 88.6% and 90.6% for fresh stillbirths.
Conclusion: In resource poor settings, the use of foot length can estimate GA in both live births and stillbirths and can easily identify preterm infants to initiate early management.