A Pilot Study to Investigate If and How Postmortem Micro-Computed Tomography (Micro-CT) Can Be Used to Differentiate Stillbirths From Livebirths

Differentiating stillbirths from livebirths is one of the most challenging tasks for forensic pathologists. Historically, the main method used in determination of live birth was the flotation test, also known as hydrostatic test. The test is based on the premise that if an infant has breathed before dying, the lungs will be inflated. Therefore, if the lungs float when immersed in water, this indicates that they are inflated, and the test is considered positive. If the infant has not breathed, the lung sinks, and the test is considered negative. However, there are arguments about the reliability of the floatation test: in fact, it can be considered at best as a suggestive pointer, but never a definitive test itself. Sometimes this method can be helped by performing microscopic examination of the lungs. The latter is based on the evaluation of alveoli’s aeration—that supposes live birth—while uniformly unaerated is indicative of stillbirth. Nevertheless, according to literature, histological studies are more indicative of fetal lung maturity than the presence or respiration. In past years, a great contribution was made by postmortem imaging. The utility of postmortem imaging is widely acknowledged, with the major advantage being that it can occur before the autopsy without disruption of the body. The postmortem Computed Tomography (PMCT) has been used to investigate the presence and the distribution of air in lungs or in the gastrointestinal tract in infants. Gas distribution may be regarded as indicating inhaled and swallowed air in the lungs and in the gastrointestinal tract, and is, therefore, used as a proof of live birth. Recently, higher resolution than PMCT has been reached through Micro-Computed Tomography (micro-CT). Indeed, common CT scans are limited to a resolution of one millimeter. Instead, micro-CT scanners can work at the level of one micron, which is a thousandth of a millimeter. However, until now, no studies in which micro-CT is used to differentiate stillbirths from livebirths are available in the scientific literature. For this reason, the authors investigated two samples by micro-CT (one from the upper lobe and one from the lower lobe of the right lungs) of two groups: ((1) group A, consisting of 14 stillbirths of > 24 weeks of gestational age; (2) group B, consisting of 4 livebirths and 10 adults. The samples were scanned by an X- Ray microtomography (SkyScan1172, Bruker). For each case, micro-CT images were analyzed by the CTvox software. In all cases of group A, the authors demonstrated the absence of areas with attenuation suggestive for the presence of air/gas. On the contrary, in group B, air/gas was identified in all fields. In light of the above, the present study allows us to suggest the micro-CT as a powerful tool to clearly distinguish between aerated and non-aerated lungs. However, further studies on broader samples are necessary to standardize techniques and procedures. References: 1- Michiue T, et al. Postmortem CT investigation of air/gas distribution in the lungs and gastrointestinal tracts of newborn infants: a serial case study with regard to still- and live birth. Forensic Sci Int. 2013;226(1-3):74-80. doi: 10.1016/j.forsciint.2012.12.011. 2 - Phillips B, Ong BB. “Was the Infant Born Alive?” A Review of Postmortem Techniques Used to Determine Live Birth In Cases of Suspected Neonaticide. Acad Forensic Pathol. 2018;8(4):874-893. doi: 10.1177/1925362118821476. 3 - Guddat SS, et al. Proof of live birth using postmortem multislice computed tomography (pmMSCT) in cases of suspected neonaticide: advantages of diagnostic imaging compared to conventional autopsy. Forensic Sci Med Pathol. 2013;9(1):3-12. doi:10.1007/s12024-012-9361-y.