How to measure the size of the pelvis during pregnancy and what standards exist?

It’s critical for both the mother and the unborn child to understand the size of the pelvis during pregnancy. It aids medical professionals in determining how well the newborn can pass through the birth canal. Although the pelvis adjusts to pregnancy naturally, measuring it provides helpful information for a more seamless delivery experience.

There are various methods for measuring the pelvis; some can be completed at home, while others call for a trip to the doctor. Expectant mothers may feel more prepared for delivery if they are aware of these techniques.

This article will examine the general standards employed by healthcare professionals, the significance of measuring the pelvic size during pregnancy, and how to do it. Make sure you’re prepared for a safe delivery by using this information to help direct your conversations with your doctor.

Doctors can determine whether a pregnant woman can give birth naturally or if she will require assistance during childbirth by measuring her pelvis. A combination of physical examinations and imaging methods, such as ultrasound, are used to accomplish this. Expectant mothers can feel more at ease knowing the basic standards for pelvic size, as these measurements help doctors plan for the safest possible birth experience.

A little about anatomy

The formation of the pelvis is bone. Its formation involves a wide variety of bones and joints. One intricate architectural component is the pelvic bone apparatus. Every woman has unique anatomical features. A pair of pelvic, sacral, and coccygeal bones combine to form the pelvic bone apparatus. The ischium, pubic, and ilium are the three additional bones that make up each pelvic bone. The cartilaginous tissue between them helps to connect them.

Such a structure is advantageous from a functional standpoint during pregnancy. It facilitates the baby’s smooth passage through the birth canal.

The reproductive organs are sort of housed in the pelvis. It plays a crucial role during a child’s development and delivery. The birth canal passes through it, and the baby moves along it as it gives birth. It is critical to ascertain the size of this bone apparatus. If the baby is not located physiologically in the mother’s womb, it is especially crucial to take this action. More cautious care must be given to the pregnant mother if she has a narrow or asymmetrical pelvis and her unborn child presents breech.

Determination of clinical parameters

For many years, medical professionals have examined the pelvis externally in a variety of ways. The first one involves palpating the pelvic parameters. The second approach involves using a pelvis meter, a specialized tool, to measure the lengths under study. This diagnostic procedure is carried out by doctors at least twice during pregnancy. These clinical parameters are established at the outset of pregnancy for the first time. The obtained values must be recorded in the expectant mother’s personal medical card. Women who are registered for pregnancy are typically the ones who have their pelvic measurements taken.

In addition, closer to delivery, doctors measure the size of the pelvic bone apparatus in expectant mothers. This is a critical prognostic indicator that helps you predict the course of the birth. It also aids medical professionals in selecting the best obstetric support strategy for a given patient. Michaelis’s rhombus is a unique anatomical area that the doctor will be particularly interested in during the examination. The lumbosacral segment of the spine contains this region.

For physicians, its alterations represent a critical diagnostic factor.

After measuring the woman’s pelvis, the obstetrician-gynecologist will monitor her for nine months while she gives birth. The examination takes place in a typical office. The expectant mother lies on the couch while the pelvis is measured. The pregnant woman lies on her back in her initial position. Lifting the expectant mother’s clothes from the area being measured will make the diagnostic process easier. The doctor uses a pelvisometer to determine the indicators.

How the norm is determined?

The obstetrician-gynecologist measures several sizes at once. One of them is longitudinal. And the other three are transverse. Each of these values ​​has its own criteria of the norm. They are used by doctors to accurately determine the type of pelvic apparatus structure in a particular patient. Several of the parameters studied are called by a special term – Distantia or abbreviated D. To determine the first of them, doctors measure the distance between both trochanteric zones of the hips. They call this parameter D. trochanterica. For most women, its values ​​are in the range of 28 to 33 cm. To determine the next parameter studied, the distance between the iliac crests is determined. It is called D. cristarum. Its normal values ​​are in the range of 24 to 27 cm.

Another equally important indicator to determine is the external conjugate. To determine it, doctors measure the distance from the upper part of the pubis to the edge of the terminal section of the lumbar region (at the level of the fifth vertebra). Its values ​​are in the range of 20 to 21 cm. After the measurement, the doctor can calculate true conjugate. This indicator is 9 cm less than the external one. In medical practice, there is another method for determining this size. For this, the doctor must determine the diagonal measurement. For this purpose, he measures the distance between the most protruding point of the sacral promontory to the lower edge of the symphysis.

This clinical indicator is typically found by a gynecologist palpating the patient while they are seated. 10 to 13 cm is the norm.

The pelvic outlet can also be measured directly by the physician. This is accomplished by measuring the distance between the lower angle of the pubis and the top of the coccygeal bone. Eleven centimeters is the equivalent of this indicator. Another refined criterion, true direct measurement, is also employed to elucidate this parameter. Already, nine and a half centimeters is its norm. Usually, there is a 1.5 centimeter mathematical difference between these two measured dimensions.

The angle of pelvic tilt is another crucial clinical indicator. Two planes, one vertical and one horizontal, combine to form it. This clinical criterion is determined using a pelvic goniometer. The normal values of this parameter in a vertical position are 45–50 degrees. The physician may also ascertain a number of additional dimensions during the examination. They are useful for diagnostic purposes in addition. They are typically required to pinpoint specific characteristics of the bone apparatus’s structure that belong to a given patient.

In the event that the specialist detects any asymmetry in the pelvic size measurement process, he will take additional measurements of the following parameters. The following table lists them:

Clinical variants

The ratio of each of these indicators is considered by the physician. This enables him to evaluate a pregnant woman’s pelvic type. Multiple dimensions are evaluated simultaneously for this purpose; the expert does not base their conclusion solely on one clinical parameter.

The table below presents different types of pelvic structure in women:

How the obtained values are deciphered?

If the pelvis has a normal structure, then the Michaelis rhombus looks like a square that is inverted. Its diagonal is about 11 cm. When measuring this indicator, it happens that the sides of the square begin to shift. This also leads to a change in its shape: it becomes more elongated. If, when measuring, the doctor determines a pair of acute and a pair of obtuse angles, then in this case this means the presence of a narrow pelvic bone apparatus. A wide pelvis is most often found in fairly tall and large women. This is influenced by the peculiarity of the structure of the musculoskeletal system of the expectant mother. Also, a wide pelvis can be found in women of average build. In miniature ladies and expectant mothers of short stature, such a structure is almost never found.

An increase in all measured dimensions is indicative of a wide pelvis. When measuring sizes, it is crucial to rule out the impact of a significant amount of subcutaneous fat. With this exception, a chair-based gynecological examination is performed. The doctor can ascertain the actual width of a patient’s pelvis by ascertaining the true conjugate. Many expectant mothers believe that their chances of giving birth naturally will increase with the size and breadth of their pelvic bones. This isn’t totally accurate.

It is true that the likelihood of a natural delivery greatly depends on the size of the pelvic bone apparatus. However, the expectant mother may still face a number of pathologies even if her pelvis is wide.

Prescriptions for cesarean sections are also not an exception in this case. A deep and capacious pelvic apparatus structure may be indicative of the need for surgery. The obstetrician-gynecologist who oversees the pregnancy makes the decision about the delivery technique. One crucial parameter that the doctor needs to note is symmetry. For this, there is a specific medical algorithm. The size of each half of the body must be measured by the doctor. In this instance, the doctor corrects the asymmetry if the left side’s measured sizes are at least one centimeter larger than the right.

Assessing the measured lateral dimensions is also crucial. The doctor will take a measurement of the distance between the posterior bones and the red hotter’s edge in order to accomplish this. Both the left and right sides contribute to the determination of these clinical parameters. This indicator typically has a value of 14 cm.

Pregnant women are also likely to have pelvic asymmetry if the measured values are significantly less than 12.5 cm or expressly differ from one another. The bones are moved in a vertical plane in this circumstance. This version of the pelvic apparatus’s structure is also referred to by doctors as asymmetric. Usually, in this case, a cesarean section will be necessary. It can be risky for a virgin to give birth, for both her and her child. In this case, there is a significantly increased risk of multiple injuries.

A crucial component of maintaining your health and the health of the unborn child is understanding how to measure your pelvis during pregnancy. Even though these measurements are typically performed by medical professionals, knowing how they work can make you feel more prepared and informed.

Doctors can determine how well positioned your body is for a natural birth based on your pelvic size. It’s important to keep in mind, though, that there are numerous factors taken into account when choosing the safest delivery method, and pelvic measurements are just one of them.

Don’t be afraid to talk to your doctor if you have any worries about how your birth plan may be affected by the size of your pelvis. On the basis of your particular health and pregnancy, they can offer more individualized information.

Video on the topic

External and internal pelviometry

Measuring the external dimensions of the pelvis

How to measure the size of the pelvis during pregnancy and what standards exist?