ObjectiveTo measure the inter-rectus distance（IRD）in normal nulliparous women by high frequency ultrasound

and to analyze its correlated factors.MethodsA total of 106 healthy nulliparous women volunteers who underwent physical examination in our hospital were enrolled.All the enrolled volunteers with BMI≤30 kg/m2.High frequency ultrasound was used to measure the IRD at 4 locations（3 cm above the umbilicus

umbilicus

2 cm and 3 cm below the umbilicus）under the supine position and abdominal curling position.The range of IRD was calculated by percentile method

and the relationship between IRD and age

height

weight and BMI were analyzed.ResultsThe normal range of IRD at supine position was as follows:3 cm above umbilicus was 4～15 mm

umbilical level was 5～20 mm

2 cm below umbilicus was 0～7 mm

and 3 cm below umbilicus was 0～3 mm

there were no significant difference compared with the values of crunches.Correlation analysis showed that IRD had no correlation with age and height

but had weak positive correlation with weight and BMI（r=0.20

0.27

P=0.04

0.01）.ConclusionHigh frequency ultrasound can accurately measure the IRD in normal nulliparous women

and IRD is weakly positively correlated with weight and BMI.