Why do we need to do external pelvic measurement?

Some women who have not given birth feel strange and embarrassed when they find out that they have to do external pelvic measurements. In fact, this is an examination done to ensure that the fetus can be delivered smoothly after pregnancy. Think about it, if your pelvis is not wide enough and is rather narrow, then the fetus cannot be delivered smoothly. There may also be signs of dystocia, so it is necessary to make measurements outside the pelvis.

However, many people do not know the steps of external pelvic measurement, nor do they know how to cooperate during this examination. To solve your confusion, please see the detailed introduction below.

1. Interiliac spine diameter

⑴ Assist the pregnant woman to lie on her back with her legs stretched out on the examination bed.

⑵ Clearly palpate the anterior superior iliac spines on both sides and measure the distance between the lateral edges of the anterior superior iliac spines on both sides.

⑶ Check the data and record it. The normal value is 23 to 26 cm.

2. Iliac crest diameter

⑴ Assist the pregnant woman to lie on her back with her legs stretched out on the examination bed.

⑵Measure the widest distance between the outer edges of the iliac crests on both sides.

⑶ Check the data and record it. The normal value is 25 to 28 cm.

The two diameter lines 1 and 2 can indirectly understand the transverse diameter length of the pelvic inlet.

3. Sacropubic external diameter

⑴ Assist the pregnant woman to lie on her left side with her right leg straight and her left leg bent.

⑵ is the distance from the midpoint of the upper edge of the pubic symphysis to the depression below the spinous process of the fifth lumbar vertebra. (Below the spinous process of the fifth lumbar vertebra, equivalent to the upper corner of the rhomboid fossa; or equivalent to 1~1.5cm below the midpoint of the line connecting the iliac crests on both sides.) This diameter can indirectly infer the anteroposterior diameter of the pelvic inlet and is the most important diameter in external pelvic measurement. The sacropubic external diameter is related to the thickness of the bone. The measured sacropubic external diameter minus 1/2 of the radial ulna circumference is equivalent to the anterior-posterior diameter of the pelvic inlet.

⑶ Check the data and record it. The normal value is 18 to 20 cm.

Exit diameter

1. Transverse diameter of the outlet (inter-ischial tuberosity diameter)

⑴ Assist the pregnant woman to lie on her back, bend her legs and hug her knees with her hands so that the hip and knee joints are fully flexed.

View the data and record it. The normal value is 8.5 to 9.5 cm.

2. Sagittal diameter after exit

⑴ At this time, ask the pregnant woman to lie on her knees or on her left side.

⑵ The examiner puts a cot on his right index finger and applies lubricating oil on it, then inserts it into the anus, with the fingertip pointing toward the sacrum and working together with the thumb to find the sacrococcygeal joint and mark it. If the sacrococcygeal joint has been fixed, use the tip of the coccyx as a mark and measure the distance from the mark to the midpoint of the transverse diameter of the outlet, which is the posterior sagittal diameter. If the sum of the posterior sagittal diameter and the transverse diameter of the outlet is greater than 15 cm, it indicates that the pelvic outlet stenosis is not obvious.

⑶ Check the data and record it. The normal value is 8-9cm.

3. Pubic arch angle

⑴ Assist the pregnant woman to lie on her back with her legs bent. Hug your knees tightly with your hands.

⑵ Place the tips of your left and right thumbs together diagonally at the lower edge of the pubic symphysis, with both thumbs flat on the descending ramus of the pubic bone.

⑶ Measure and record the angle between the two thumbs. The normal value is 90°. Less than 80° is abnormal, and this angle reflects the width of the transverse diameter of the pelvic outlet.

⑷ Assist pregnant women to tidy up their clothes and belongings and put them back to their original places.

Why do we need to do external pelvic measurement? Now you should know why we need to do external pelvic measurement. It’s just that the measurement process is rather complicated, and I hope everyone can read it patiently. Although everyone does not know the meaning of some professional terms, this does not affect everyone's understanding of the issue. If you want to have a baby recently, it is best to check whether your pelvic distance is normal. If your pelvis is too narrow, you can also have a caesarean section.