The anti-clockwise spiralization of the linea nigra sign

OBJECTIVE: To describe the morphology of the supra- and infraumbilical linea nigra in puerperal women. METHODS: The study was conducted from September 2017 to April 2018, and included 157 puerperal women admitted for childbirth care at the Obstetrics Department of a public maternity hospital of the city of São Paulo (SP), Brazil. The abdomen of subjects was photographed on the first or second day postpartum, with the patient lying symmetrically in dorsal decubitus at a standardized distance. Contrast was slightly adjusted and the morphological pattern of supra and infraumbilical linea nigra in the proximity of the umbilical scar was characterized. The images were independently analyzed by two researchers and only the matching results from both observers were used. RESULTS: Of the 157 observed cases, 139 (88.5%) images provided concordant results between the two researchers. Excluding 41 cases of absence or poor definition of the linea nigra, 98 images were analyzed. Supra- and infraumbilical linea nigra were analyzed separately and classified according to three directions (left, center and right of the umbilical scar). The combination of the supra- and infraumbilical images resulted in the formation of nine distinct patterns, being the most prevalent, in primiparous (72.2%) and multiparous women (50.0%), and the authors named as “anticlockwise spiralization of the linea nigra”. CONCLUSION: The analysis of supra- and infraumbilical linea nigra in puerperal women showed a predominance of what the authors named “anti-clockwise spiralization of the linea nigra sign”.