Abstract
The function of the linea alba is to maintain the abdominal muscles at a certain proximity to each other. In the case of longโlasting increased intraโabdominal pressure, the linea alba widens. Yet, as the existence of the linea a priori implicates a physiological distance between the two rectus muscles, the question arises as to what the normal width of the linea alba is. To evaluate the normal width of the linea alba, we examined 150 nulliparous women between 20 and 45 years of age with a body mass index < 30 kg m^โ2^ by ultrasound at three reference points: the origin at the xiphoid and 3 cm above and 2 cm below the umbilicus. The examination revealed a broad range of widths at the three reference points. The linea was widest at 3 cm above the umbilicus (โ35 mm), followed by the reference point 2 cm below the umbilicus (โ31 mm) and the origin at the xiphoid (โ31 mm). The mean width was 7 ยฑ 5 mm at the xiphoid and 13 ยฑ 7 mm above and 8 ยฑ 6 mm below the umbilicus. For the definition of the normal width of the linea, the 10th and 90th percentiles were taken. The linea alba can be considered โnormalโ up to a width of 15 mm at the xiphoid, up to 22 mm at the reference point 3 cm above the umbilicus and up to 16 mm at the reference point 2 cm below the umbilicus in nulliparous women. Clin. Anat. 22:706โ711, 2009. ยฉ 2009 WileyโLiss, Inc.