Estimation of gestational age in neonates using clavicular-pubis length on routine chest-abdomen radiographs

Neonatal diseases differ depending on gestational age and weight. In the setting of an emergency in the neonatal intensive care unit (NICU), relevant clinical information is often not available when the first neonatal radiograph is obtained. When reading an initial chest-abdomen radiograph, the paediatric radiologist needs gestational age data for best radiologic practice. A transverse diameter of the chest has been previously described to estimate gestational age (GA).

To determine the strength of the correlation between GA/weight and clavicular-pubis length (CPL) on admission radiographs; to obtain a quadratic formula based on the correlation of CPL with GA and to demonstrate if a more simplified formula used by our group works as efficiently as the formula provided by the regression analysis.

A retrospective study was approved by the institutional review board and informed consent was waived. The length from the medial aspect of the clavicle to the pubic bone was measured on the initial portable chest-abdomen radiographs of 260 patients admitted to the NICU in 2016. Regression analysis was performed to investigate the association between CPL and GA/birth weight.

One hundred eleven females and 149 males with GA between 23 and 42 weeks were evaluated. CPL was statistically associated with both GA (P<0,01) and birth weight. The estimation can be expressed with an equation of the model: GA (weeks) = (CPL in cm - 1.98)/0.42. A simplified formula: GA (weeks) = (CPL in cm) ×2+2, strongly correlates with the equation model.

In patients in whom it is not known, GA can be estimated by measuring the length between medial clavicle and symphysis pubis using the formulae we propose.