Management of pregnancy and childbirth with a narrow pelvis

The problem of a narrow pelvis remains one of the most pressing and at the same time most difficult in obstetrics, despite the fact that this issue has undergone a certain evolution.

In recent years, due to the preventive direction of domestic medicine, the number of anatomically narrow pelvises has decreased. At the same time, narrow pelvises with gross deformation and sharp narrowing - flat rachitic, kyphotic - are almost never encountered. Generally uniformly narrowed pelvises have become less common, and the degree of narrowing is less. Acceleration and an increase in the ratio of height to body weight in women contributed to the development of pelvises of greater capacity. Thus, according to data from modern authors based on ultrasound and X-ray methods, it was shown that the average value of the true conjugate is currently 12 ± 0.8 cm, and a true conjugate of more than 13 cm occurs only in every tenth woman and less than 11 cm - in 6.1%.

At the same time, the absence of grossly deformed pelvises, with the exception of only fractures of the lumbosacral spine and pelvic bones in childbearing age, which are the result of severe trauma received in car accidents, it should still be said that the problem of a narrow pelvis remains relevant, since in the process of acceleration new forms of narrow pelvises have appeared:

• transversely tapered;
• assimilation or long pelvis according to Kirchhoff;
• pelvis with a decrease in the direct diameter of the wide part of the pelvic cavity.

At the same time, a tendency towards an increase in the frequency of these forms of narrow pelvises has been noted.

The above pelvises do not have gross anatomical changes that would usually be easily detected during external and internal examination with a pelvimeter and other methods. Their shape and structure represent various variants of flat, male-type, infantile pelvises, as this is due to the rapid growth of modern women, i.e. the rapid growth in length of the female skeleton: the transverse dimensions of the pelvis have decreased, while a narrow, vertically standing sacrum, a narrow pubic arch, vertically standing iliac bones, the so-called transversely narrowed pelvis, etc. have formed. Therefore, the determination of these forms of narrow pelvis is currently unthinkable without additional objective examination methods - the use of ultrasound research methods, X-ray pelvimetry, etc. At the same time, an increase in the frequency of large fetuses is noted, which has led to an increase in the frequency of the so-called clinically narrow pelvis.

Before moving on to the assessment of a narrow pelvis, it is necessary to recall the normal biomechanics of childbirth. It is necessary to take into account the woman's constitution. In women of the asthenic type, there is a predominance of body growth in length with a narrow torso. The skeleton is narrow and light. The spine often forms a kyphosis in the cervicothoracic region, as a result of which the body is bent forward. The angle of inclination of the pelvis is 44.8, lumbar lordosis is 4.3 cm, the body mass index is low.

In women of the hypersthenic type, the body dimensions are predominantly in width. The skeleton is wide and strong. There is an increased physiological lumbar lordosis, as a result of which the body is tilted backwards. The angle of inclination of the pelvis is 46.2°, the lumbar lordosis is 4.7 cm.

With a normosthenic type of constitution, pregnancy and childbirth proceed normally.

It is necessary to pay attention to the shape of the Michaelis rhombus. Thus, with a flat rachitic pelvis, the upper point of the rhombus often coincides with the base of the upper triangle. With obliquely contracted pelvises, the lateral points of the rhombus are shifted accordingly - one higher, the other lower.

Management of labor with a narrow pelvis

The course and management of labor with a narrow pelvis depends not only and not so much on the reduction of its size (excluding III and IV degrees of absolute narrowing with a true conjugate of 7-5 cm or less), but on the weight of the fetus, or more precisely, its head, its configuration, as well as sufficient labor activity. To this should be added the need for maximum preservation of the fetal bladder, since untimely discharge of waters leads to the complications indicated above and significantly worsens the outcome of labor for both the mother and the fetus. The overwhelming majority of births with I degree of narrowing of a generally uniformly narrowed and flat pelvis (if we exclude concomitant possible pathology) end spontaneously with the birth of a live full-term fetus in 75-85% and even 90%. However, at present, due to the increased number of large fetuses, relative clinical discrepancy may more often appear, requiring vaginal operative delivery - the application of obstetric forceps or a vacuum extractor (preferably a weekend one).

For the purpose of childbirth, a number of countries still offer and use pelvic dilatation operations - subcutaneous symphysiotomy and pubiotomy, which are not used in our country.

If absolute discrepancy is detected, delivery is by caesarean section. With the second degree of narrowing, spontaneous delivery is possible if the head is small, then the pelvis may be functionally sufficient. In these cases, it is especially important to avoid post-term pregnancy and the development of weakness of labor activity. Conducting labor with a generally narrowed-flat pelvis is an extremely important task for the doctor; their course is usually difficult, spontaneous delivery is possible in about half of the cases.

When monitoring a pregnant woman, the doctor must take into account the above-mentioned features of narrow pelvises, their functional capabilities in comparison with the weight of the fetus and promptly hospitalize the woman in a maternity hospital. For this purpose, along with measuring the pelvis and the weight of the fetus, it is necessary to also use some other signs characterizing the functional capabilities - ultrasound examination, the Hofmeyer-Muller sign with careful use. It is not recommended to use the Hofmeyer-Muller method, using a similar functional test (safer and physiological) in labor, asking the woman in labor to push 2-3 times, usually with significant or complete dilation of the cervix during a contraction with the doctor's hand inserted into the vagina. The absence of any advancement of the head or, on the contrary, its known descent indicates a different functional capacity of the pelvis.

The second sign - Vasten-Henkel, in the opinion of most obstetricians, is of great importance, and this should be agreed with. It is important to note that its use is especially valuable when the head is fixed by at least a small segment at the entrance to the pelvis, the water has broken and there is good labor activity. It should be considered that the Vasten-Henkel sign is very indicative and the obstetrician can use it repeatedly in the dynamics of the course of labor, starting from the standing of the head by a small segment until it reaches a large segment and passes this line, after which it will become quite clear that the main narrowing of the pelvis by its largest dimensions has been overcome. Since this sign does not provide convincing orientation when the head is standing above the entrance to the pelvis or at the entrance to the pelvis, it is more appropriate in these cases to talk not about the sign as such, but about whether there is an overhang of the head over the pubis or not. However, with some incorrect insertions of the head (high straight position of the sagittal suture - occipito-sacral position - with a transversely narrowed pelvis"; anterior-parietal inclination - with a flat-rachitic pelvis; face presentation) the Vasten sign does not provide a correct orientation about the relationship between the head and the pelvis. More often it appears negative, although the functional balance has not yet been determined.

The obstetrician should remember that the clinical course of labor with a narrow pelvis is longer than usual, and the longer it is, the greater the degree of narrowing of the pelvis, the more pronounced the clinical discrepancy between the head and the pelvis during labor. This is explained by the time required to develop the mechanism inherent in each type of pelvis. It is also necessary to have sufficient labor activity and head configuration. Difficulties in the formation of the head and the mechanism of labor, the duration of these processes lead to fatigue of the woman in labor. Particularly unfavorable in this regard is a generally narrowed flat pelvis with a labor duration of up to 1-2 days, with a posterior-parietal insertion more often developed, which is less favorable for the advancement of the head. With a transversely narrowed pelvis and a high, straight position of the sagittal suture, which is considered favorable for this form of the pelvis, the head often passes through the entire pelvis in a straight size.

It should be taken into account that at present, among narrow pelvises, the most common is a transversely narrowed pelvis with a decrease in the direct size of the wide part of the cavity of the small pelvis. Let us recall that the wide part of the cavity of the small pelvis is called that part of it, which is located below the plane of entry, or more precisely behind the plane of entry. This part occupies the space limited in front by a transverse line dividing the inner surface of the pubic symphysis into two equal parts, behind - by the line of connection of the II and III sacral vertebrae, on the sides - by the middle of the bottom of the articular acetabulum. The line connecting all the listed formations is a circle corresponding to the plane of the wide part of the small pelvis.

The following dimensions are determined in this plane:

1. straight - from the upper edge of the third sacral vertebra to the middle of the inner surface of the pubic symphysis, normally it is 13 cm;
2. transverse between the midpoints of the acetabulums, it is equal to 12.5 cm;
3. oblique - from the upper edge of the greater sciatic notch on one side to the groove of the obturator muscle on the opposite side, they are equal to 13.5 cm.

Here we should also mention the concept of the plane of the narrow part of the pelvic cavity, which is of great importance for obstetrics. The narrow part of the pelvic cavity is the space located between the plane of its wide part and the plane of the outlet. It has the following limiting points: in front - the lower edge of the pubic symphysis, behind - the top of the sacrum; on the sides - the ends of the ischial spines. The line connecting the above-mentioned formations is a circle, which corresponds to the plane of the narrow part of the pelvis.

This plane has the following dimensions:

1. straight - from the top of the sacrum to the lower edge of the pubic symphysis, normally it is 11.5 cm;
2. transverse - the line connecting the ischial spines, this size is 10.5 cm.

When the woman in labor is tired, she needs to be given medicated sleep-rest. We adhere to dosed sleep-rest after 14-16 hours of the woman's stay in labor, and for somatically burdened women in labor or with late toxicosis, even earlier, if they are tired, especially at night and in the evening. The duration of sleep is dosed from 3-4 to 6 hours depending on the obstetric situation, in particular the state of the amniotic sac and the duration of the anhydrous period, as well as the presence or absence of an increase in body temperature during labor. It is advisable to use antispasmodics during labor.

Often, the development of weakness of labor activity leads to the need for labor stimulation, which is considered acceptable only if there are no signs of overstretching of the lower uterine segment. When conducting labor with the use of labor stimulating agents, it is necessary to pay attention to mild degrees of discrepancy against the background of labor stimulation or, if a high border groove of Schatz-Unterberger is found, to stop the introduction of oxytotic agents in time. In the second stage of labor, the application of a Verbov bandage is applicable.

With a certain amount of caution, in case of weak labor activity with the first degree of pelvic contraction and without oxytotic agents, an estrogen (on ether) - glucose-vitamin-calcium background can be used first, followed by, after 1/2-1 hour, the usual labor stimulation (castor oil 30 ml, cleansing enema, quinine 0.05 g 4 times, up to 6-8 quinine powders every 15 minutes). The decision on activating labor in women who have given birth repeatedly and have given birth many times should be made especially strictly, taking into account the thinning of the lower segment and the threat of its rupture and only in the obvious absence of discrepancy between the mother's head and pelvis.

It is necessary to prevent fetal hypoxia during labor. Previously strictly conservative expectant tactics have now been replaced by a less conservative one, in order to avoid damage to the mother's body, in order to obtain a live and healthy newborn child. One of the most gentle methods of delivery is a cesarean section. This operation is especially indicated in the case of a combination of an anatomically narrow pelvis with an incorrect insertion of the head, as well as in pelvises narrowed in the pelvic outlet cavity (kyphotic and funnel-shaped), in breech presentation of the fetus, especially a large one and in primiparous older women, in the presence of a scar on the uterus.