Immaturity of connective tissue as a cause of damage to the dural mining in newborns with extremely low body weight

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BACKGROUND

According to order no. 1687n of the Ministry of Health and Social Development of the Russian Federation¹, the medical criterion for birth is a pregnancy term of 22 weeks or more, with a birth weight ≥500 g (or <500 g in the case of multiparity). In cases where the gestation period is less than 22 weeks or the birth weight of the child is less than 500 g, including those with unknown birth weight and a body length <25 cm, the criterion for birth is a life expectancy >168 hours after birth (7 days).

Official statistics show that the number of infants born prematurely is increasing worldwide. In the United States, the incidence of premature births is approximately 11%, and in Europe, it ranges from 5% to 7%. Despite advances in obstetric care, the rate of premature births has not decreased over the past 40 years [1].

Extremely low birth weight (ELBW) infants are more likely to die during the first week of life [1–3]. The mortality rate of ELBW infants is 8–13 times higher than that of term infants [4, 5]. Extreme prematurity is a leading risk factor for birth trauma. The brain and spinal cord are most often damaged during childbirth [3, 6–9].

Nervous system damage caused by inadequate medical care is a reason for initiating criminal and civil cases against obstetricians and gynecologists. At present, the issues of liability of medical staff are becoming increasingly crucial.

The American College of Obstetricians and Gynecologists reported that 80% of its members have faced lawsuits, with an average of three litigations per member. Most of the high-profile clinical negligence convictions, often for tens of millions of dollars, are related to birth injuries [10].

Currently, pathologists and forensic experts experience difficulties in examining such newborns, because they were not subjected to autopsy before the abovementioned legislative instrument took effect. According to international literature, the frequency of autopsies of deceased patients in neonatal intensive care units is decreasing. Postmortem magnetic resonance imaging is used as a supplement to or replacement for autopsy [11].

Recent studies in the Russian language have described the biomechanisms of birth injuries in full-term newborns, regardless of fetal presentation and operative delivery, and introduced scientific and practical developments of novel methods of sectional access to the jugular ganglia of the vagus nerve and vertebral arteries [12–15].

This study aimed to identify the characteristic features of the structure of the connective tissue of the dura mater in ELBW and full-term newborns and establish the relationship between the structural features of the dura mater and its damage during childbirth.

MATERIALS AND METHODS

Study design

An observational multicenter retrospective selective controlled non-randomized study was conducted.

Archival autopsy materials and materials of criminal and civil cases regarding fatal outcomes of ELBW newborns and full-term newborns with birth injury were analyzed. The study was conducted at the Krasnoyarsk Regional Office of the Chief Medical Examiner (KRO CME) and Regional Office of the Chief Medical Examiner of the Ministry of Health of the Khabarovsk Territory (Office of CME MH KT).

Eligibility criteria

The inclusion criteria were archival autopsy material and materials of criminal and civil cases regarding fatal outcomes of ELBW newborns and full-term newborns with confirmed birth injury.

The exclusion and non-inclusion criteria included archival autopsy material and materials of criminal and civil cases regarding fatal outcomes of premature newborns with a birth weight >1000 g, severe developmental defects, full-term newborns without an established diagnosis of birth injury, and stillborn fetuses.

Study conditions

Archival autopsy material, materials of criminal and civil cases, and histological glass slides/paraffin blocks were investigated at KRO CME and the Office of CME MH KT.

Study duration

The study used histological materials obtained from 2020 to 2023.

Description of medical intervention

A retrospective selective analysis of autopsy materials and criminal and civil case materials on fatal outcomes of ELBW and full-term newborns was conducted. The method and causes of delivery in the main and comparison groups were assessed. Hemorrhages in the dura mater caused by birth trauma were macro- and microscopically evaluated. Furthermore, distinctive features of the structure of the dura mater were explored, and morphometry of collagen fibers in both groups was performed in 30 fields of view of the microscope.

Standard histological processing of the material under study was carried out. The material was embedded in paraffin blocks, and histological microslides were made. Histological sections were stained with basic and acidic stains (hematoxylin and eosin). The sections were reviewed, studied, and described, and microphotographs were created on the ECLIPSE E200 microscope (Nikon, Japan). Polarization microscopy was performed using an ocular insert to determine the composition of collagen fibers in the dura mater tissue with subsequent morphometry of type I collagen. Obtained data were systematized and registered.

Main outcome of the study

Morphometry of type I collagen fibers in the dura mater showed significantly smaller number in ELBW neonates than in full-term neonates in 30 fields of view of the microscope, which causes immaturity and its damage during any type of birth.

Additional outcomes of the study

Additional expected results of the study of medical intervention were not registered.

Analysis in subgroups

A retrospective selective analysis of cases in autopsy materials and criminal and civil cases was performed, for which two study groups were formed: the main and comparison groups. The main group consisted of deceased ELBW (500–1000 g) newborns, regardless of the method of delivery (n=30), and the control group included deceased full-term newborns with a body weight of 2900–3600 g and confirmed birth injury, regardless of the method of delivery (n=30).

Methods of registration of outcomes

The operating shell Microsoft Windows Professional 2010 Excel was used to record the outcomes. Calculations were performed using the SPSS v.26 package.

Ethical considerations

The Independent Ethics Committee approved the PhD thesis “Biomechanism and forensic medical assessment of birth injuries in extremely low birth weight newborns” in the specialty 3.3.5 “Forensic Medicine” at the Department of Forensic Medicine of the Moscow Regional M.F. Vladimirsky Research and Clinical Institute. There was extract from the minutes of the meeting no. 15, dated 10/07/2021.

Statistical analysis

The probability of birth injury varies in the study groups (full-term and preterm infants); hence, a stratified sample was used with a separate calculation of the number for each stratum. In 2022, 4765 premature babies were born in Russia. Considering that 99.9% of them had a birth injury, at a significance level of 0.05 and a marginal sampling error of 1.2%, the minimum required sample size of the main group was 27 children.

In 2022, 47,247 children were born full-term in Russia. Considering that the prevalence of birth injury was 70%, at a significance level of 0.05 and a marginal sampling error of 17%, the minimum required sample size of the control group was 28 children. We rounded the sample sizes to 30 children. Differences in the marginal errors in each sample stratum were due to the different incidence of birth injury in each group.

The calculations were performed using the SPSS Statistics v.26 package, Microsoft Excel. A classical statistical method, such as the Mann–Whitney statistical test, was used. Indicators were considered statistically significant at p <0.001.

RESULTS

Research objects (participants)

Overall, 60 cases were studied. The main group included autopsy materials and criminal and civil case materials from 30 ELBW (500–1000 g) newborns, with a gestation period of 22–27 weeks. Premature delivery in this group was caused by acute uteroplacental insufficiency with the development of accelerated labor and requiring an emergency cesarean section in 60% and 40% of cases, respectively.

The comparison group included autopsy materials and criminal and civil case materials from 30 full-term newborns weighing 2900–3600 g with a confirmed birth injury. Delivery in the control group was through the natural birth canal and by elective cesarean section.

Main results of the study

In all the studied cases, ELBW neonates had pronounced intradural hemorrhages in the dura mater with localization in the falx, sinus drainage area, and cerebellar tentorium. Minimally severe “step symptom” with minor hemorrhages in the pia mater was determined. The dura mater from the area of the velum of the cerebellar tentorium, falx, and sinus drainage area had loose connective tissue consisting mainly of type III collagen fibers with a small amount of type I collagen fibers. Under polarization microscopy, type III collagen had short fibers with the absence of anisotropy at 400-fold magnification of the microscope. Collagen type I had single small fiber bundles with a clear polarization effect at 400x magnification of the microscope. Anisotropy in polarized light was detected in no more than 2%–5% of collagen fibers (Fig. 1).

 

Fig. 1. Dura mater of a deceased newborn with extremely low birth weight, sinus drainage area. Yellow filter. a ― staining: hematoxylin-eosin, magnification, ×400; b ― staining: hematoxylin-eosin, polarization, 10×10. (Photo from personal archive of the authors).

 

A comparison of the results indicated that in full-term newborns in the comparison group, the severity of subarachnoid hemorrhages in the projection of the sutures corresponded to the severity of damage to the septal parts of the dura mater. Histological examination showed that the dura mater from similar localizations consisted of dense fibrous connective tissue (Fig. 2). Anisotropy in polarized light was at least 30%–50%.

 

Fig. 2. The dura mater of a deceased full-term baby, the sinus drainage area. Blue filter. Staining: hematoxylin-eosin, ×400. (Photo from personal archive of the authors).

 

During statistical analysis, the minimum, maximum, and average values of the amount of collagen type I in the main group and comparison groups were compared. The indices were evaluated for compliance with normal distribution using the Kolmogorov–Smirnov test (with significance correction according to Lilliefors) and Shapiro–Wilk test. In both groups, the hypothesis of compliance with normal distribution was rejected. Therefore, structural indices (median and quartiles designated as Me [Q25; Q75]) and minimum and maximum values were used to characterize the indices. The nonparametric Mann–Whitney test was used to compare the groups by the indices of the percentage of mature fibers (Table 1). The minimum value for 30 visual fields varied from 2% to 5% in the main group (median: 2%) and from 30% to 40% in the comparison group (median: 39%). The maximum value for 30 visual fields varied in the main group from 3% to 5% (median: 4.5%) and from 40% to 50% in the comparison group (median 50%). The average value in the main group varied from 2.5% to 4.5% (median: 3.5%) and from 35% to 45% in the main group (median: 40%). A significant difference (p <0.001) was noted in the indices of presence of type I collagen fibers in the main and comparison groups. Figure 3 presents the diagram of the range of the average value of the percentage of mature fibers in the main and comparison groups.

 

Table 1. Comparison of the amount of type I collagen in the study group sample

Mature fibres in 30 fields of view, %	Main group			Control group			р
	Min	Max	Me [Q25; Q75]	Min	Max	Me [Q25; Q75]
Minimum value	2.0	5.0	2.00 [2.00; 3.00]	30	40	30.00 [30.00; 40.00]	<0.001
Maximum value	3.0	5.0	4.50 [4.00; 5.00]	40	50	50.00 [50.00; 50.00]	<0.001
Mean value	2.5	4.5	3.50 [3.00; 3.63]	35.0	45.0	40.00 [40.00; 45.00]	<0.001

 

Fig. 3. Comparison of mean values of type I collagen fibers across 30 visual fields in a study group sample.

 

Additional results of the study

No additional outcomes were registered.

DISCUSSION

During childbirth, compressive forces influence the presentation of the baby’s head. The increasing stress leads to tension of the dura mater duplications, namely, the velum of the tentorium cerebellum and falx [13, 14]. These structures are connective tissue consisting of cells, ground or amorphous substance, and collagen fibers [16]. Pronounced intradural hemorrhages in the dura mater duplications in the main group indicate their overstretching due to the displacement of the skull bones along the sutures. The dura mater of premature infants consists of loose connective tissue and the presence of only 3%–5% of mature type I collagen fibers, in contrast to full-term infants, whose dura mater consists of dense connective tissue and the presence of 30%–50% mature type I collagen fibers.

The differences and structural features of the connective tissue of the dura mater duplications in ELBW newborns indicate its morphofunctional immaturity, which reduces its strength characteristics and causes trauma during any type of delivery. These differences reveal the cause of damage to the septal parts of the dura mater in ELBW premature newborns.

CONCLUSION

Owing to the pronounced physiological immaturity of the connective tissue of the dura mater in ELBW newborns, its damage occurs regardless of the method of delivery and with technically correct obstetric management. Consequently, this injury is an injury to a painfully altered organ. Therefore, it is not subjected to forensic expert assessment of the severity of harm to health.

ADDITIONAL INFORMATION

Funding source. This article was not supported by any external sources of funding.

Competing interests. The authors declare that they have no competing interests.

Authors’ contribution. All authors made a substantial contribution to the conception of the work, acquisition, analysis, interpretation of data for the work, drafting and revising the work, final approval of the version to be published and agree to be accountable for all aspects of the work. E.Yu. Gorun ― data collection, drafting the manuscript, scientific editing; S.L. Parilov ― data collection, scientific editing; S.L. Parilov, A.V. Maksimov ― review and approval of the final version of the manuscript.

¹ Order of the Ministry of Health and Social Development of the Russian Federation, dated December 27, 2011, no. 1687n, “On medical criteria for birth, the form of the birth document and the procedure for issuing it” (as amended on October 13, 2021). Access mode: https://docs.cntd.ru/document/902320615?ysclid=lyn4dbab4a160264169.

About the authors

Ekaterina Y. Gorun

Moscow Regional Research and Clinical Institute

Author for correspondence.
Email: katuhka30@mail.ru
ORCID iD: 0000-0002-7008-2975
SPIN-code: 4298-5402
Россия, Moscow

Sergey L. Parilov

Moscow Regional Research and Clinical Institute

Email: parilov.s@mail.ru
ORCID iD: 0000-0001-9888-4534
SPIN-code: 1764-7532

MD, Dr. Sci. (Medicine), Assistant Professor

Россия, Moscow

Alexandr V. Maximov

Moscow Regional Research and Clinical Institute; State University of Education

Email: mcsim2002@mail.ru
ORCID iD: 0000-0003-1936-4448
SPIN-code: 3134-8457

MD, Dr. Sci. (Medicine), Assistant Professor

Россия, Moscow; Moscow

References

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