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Predicting labor with internal hysterography
Last reviewed: 08.07.2025
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The method of two-channel internal hysterography allows predicting labor activity for the entire process of labor. It is enough to record the intrauterine pressure in 2 channels for 30-60 minutes from the onset of labor, and then compare the records of intrauterine pressure in the area of the fundus and the lower segment of the uterus. The course of labor is predicted by the ratio of the amplitude of uterine contractions. If the amplitude of uterine contractions is higher in the lower segment than in the fundus of the uterus, labor is proceeding and will proceed normally, but if the amplitude of uterine contractions is higher in the area of the fundus of the uterus than in the lower segment or is equal to it, there is weakness of labor.
Thus, during normal labor, the intrauterine pressure in the lower segment when the cervical os is opened to 2-4 cm is 43.63 ± 1.01 mm Hg; at 5-7 cm - 48.13 + 1.05 mm Hg; at 8-10 cm - 56.31 ± 1.01 mm Hg.
In the fundus of the uterus, respectively - 36.6 ± 0.9 mm Hg, 40.7 ± 0.76 mm Hg, 47.15 ± 1.4 mm Hg (p < 0.05).
In the practical activities of a doctor, the following formula is used to quickly assess the contractile activity of the uterus during labor:
E = Ea × e / T (conventional unit), where
E is the efficiency of uterine contractile activity in conventional units, E is the mathematical sign of the sum, f is the amplitude of a single contraction in g/cm2 , T is the time of the analyzed process in seconds.
The efficiency of uterine contractility increases as labor progresses, with the fundus being more efficient than the corpus and the corpus more efficient than the lower uterine segment, although these differences are not statistically significant in all cases.
Thus, with a sharply shortened cervix, the efficiency of contractile activity of the uterus in the fundus area was 13.5 ± 0.43, the body - 13.2 ± 0.45 and the lower segment of the uterus - 7.4 ± 0.18. With opening of the uterine os by 2-4 cm, respectively 29.8 ± 0.51; 18.8 ± 0.39 and 13.8 ± 0.28.
When the cervical os is opened by 5-7 cm, respectively: 30.4 ± 0.63; 19.4 ± 0.48; 14.0 ± 0.31.
When the cervical os is opened by 8-10 cm, respectively: 36.2 ± 0.59; 24.1 ± 0.32 and 16.8 ± 0.32.
Modern research shows that normal amniotic pressure increases as pregnancy progresses and the amount of amniotic fluid increases up to 22 weeks, and then does not change significantly. Amniotic pressure and its changes associated with uterine activity have been studied for 40 years.
Amniotic pressure may be high in polyhydramnios and low in oligohydramnios. Various complications during pregnancy are mediated by amniotic pressure. During full-term pregnancy and early stages of labor, the basal tone is 8-12 mm Hg. Gibb (1993) believes that internal hysterography should be used in the clinic in no more than 5% of all births, especially in women in labor with a scar on the uterus, in breech presentations, in multiparous women, in cases of insufficient uterine contractions, induced labor, and labor management using oxytocin.
To assess the condition of the fetus, it is important to consider clinical data on the height of the fundus at different stages of pregnancy. Below are the stages of pregnancy, the height of the fundus in cm (symphysis-fundus) with confidence intervals:
Some studies have shown that measuring the height of the fundus does not improve the prediction of low birth weight babies. At the same time, Indira et al. (1990) showed that the height of the fundus above the symphysis is a real parameter for assessing the size of the fetus.
It is also important to consider antenatal and intranatal factors that can lead to various types of trauma to a newborn child. In the population, the risk of getting a traumatized child is 1 in 1000 newborns, and in the presence of risk factors - 1 in 100 newborns. Patterson et al. (1989) include the following as risk factors:
- anemia of pregnancy;
- obstetric bleeding during pregnancy;
- bronchial asthma;
- the presence of meconium in the amniotic fluid;
- extension presentation of the head;
- posterior occipital presentation;
- fetal distress;
- shoulder dystocia.
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