Reference Data on the Normal Abdominal Wall Anatomy and Baseline Characteristics in Seventy-One Nulliparous Women

Aims: The aim of this study was to describe the prepartum anatomy of the abdominal wall in a cohort of nulliparous women, for use as a reference for management of patients with postpartum abdominal wall insufficiency with or without rectus diastasis. Materials and Methods: Seventy-one women were examined with ultrasonography of the abdominal wall. The inter-recti distance (IRD), anatomical variations of the linea semilunaris, and the oblique muscles were assessed. The waistline was measured during activation and relaxation of the abdominal core. Participant characteristics were registered. Questionnaires regarding habitual physical activity (Baecke), low back pain (Oswestry), physical functioning (DRI), urinary incontinence (UDI-6 and IIQ-7), and quality-of-life (SF-36) were answered. Results: Mean age was 30.5 years (range 19-50 years) and mean BMI 23.5 kg/m² (range 18-37). Ultrasonography showed a mean IRD of 10 mm (range 3-24) at the superior border of the umbilicus, 9 mm (4-20) 3 cm above the umbilicus, and 2 mm (-5-10) 2 cm below the umbilicus. The mean thickness of the linea alba was 3 mm (1.5-5) and mean distances between the lateral edge of the rectus muscle and the external, internal, and transverse oblique muscles were 12 mm (-10-28), 1 mm (-14-13) and 15 mm (-14-32) at umbilicus level. Responses to the DRI, UDI-6, IIQ-7 and Oswestry questionnaires showed generally lower scores than the normal population whereas Baecke and SF-36 scores were similar. Conclusion: This study provides baseline data on normal abdominal wall anatomy in a healthy nulliparous female cohort, as well as levels of activity, physical function, disability, and quality-of-life.