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Neonaticide and the question of live birth

  • Method

When a newborn is found dead, the autopsy tries to tell whether it was viable and born alive; no classic test proves it alone, and the float test is unreliable.

Updated

What it is

When the body of a newborn is found, the investigation must answer whether it was viable (gestational age and maturity), whether it was born alive or dead, how long it lived and what caused its death. Having breathed is the classic criterion of live birth, but no test proves it with certainty. The lung flotation test (hydrostatic test) relies on the fact that a lung that has breathed contains air and floats; it can give false positives from putrefactive gas or air introduced during resuscitation, and false negatives if the baby breathed only briefly. Postmortem imaging and lung histology add information, but are interpreted together. Maceration shows that the fetus died inside the uterus before birth.

Accuracy and limits

  • Positive flotation: may be due to putrefactive gas, even from gas-forming bacteria in a fresh body, or to resuscitation air.
  • Negative flotation: does not rule out brief breathing, which may not aerate the lung enough to float.
  • Postmortem MRI was highly accurate in detecting lung aeration in a small study; it still needs validation.
  • Micro-CT of lung samples is a method under study.
  • No single sign proves live birth: the conclusion rests on all the findings and is sometimes «undetermined».

What it is based on

  • With breathing, the alveoli expand and the lung becomes paler, crepitant and less dense than water.
  • Swallowed air moves through the stomach and bowel over time, and the umbilical cord dries in the following days.
  • Maturity is estimated from length, weight, external features and ossification centres.
  • Maceration (skin slipping, soft body) occurs when the fetus dies inside the uterus and remains in the amniotic fluid.

How it is applied

  1. Record the scene, the state of the body and, if found, the placenta and cord, with photographs.
  2. Measure and weigh the body and assess maturity and gestational age.
  3. Take radiographs or CT before opening the body to look for air in the lungs and gut.
  4. Describe maceration, putrefaction, injuries and signs of resuscitation.
  5. Remove the lungs en bloc with the heart and airway, and take samples for histology.
  6. If the flotation test is done, record the degree of putrefaction and whether there was resuscitation, and interpret it cautiously.
  7. Look for milk or food in the stomach and examine the cord and its end: cut or torn.
  8. Assess the cause of death (asphyxia, injuries, hypothermia, abandonment or natural cause) and take samples for toxicology.

Next step: what to do and document

  • When a dead newborn is found outside a hospital, inform the Fiscalía for the medico-legal autopsy, mandatory when homicide is suspected (Decree 786 of 1990, art. 6).
  • Keep the placenta, cord and any clothing or wrappings under chain of custody.
  • Care for the mother urgently and with dignity: she may have postpartum haemorrhage or infection and needs medical and psychological care.
  • Examine the mother only with her informed consent and as part of her care, without pressure.
  • In the report, separate findings from interpretation and state explicitly what could not be established.
  • Official text checked on 2026-11-13 at funcionpublica.gov.co.

Common mistakes

  • Concluding live birth from a positive flotation test alone.
  • Doing the test on a putrefied or resuscitated body without stating the limitation.
  • Mistaking maceration for injuries or for putrefaction that occurred after birth.
  • Questioning the mother about the events during clinical care instead of caring for her.

Test yourself

Think of the answer, then tap the question to see it.

Why does the lung flotation test not prove that a newborn was born alive?

Because putrefactive gas or resuscitation air can make a lung that never breathed float, and brief breathing may not make it float.

What does maceration of a fetus indicate?

That it died inside the uterus and stayed in the amniotic fluid before birth; it argues against live birth.

Which questions must the autopsy of a newborn found dead answer?

Whether it was viable, whether it was born alive or dead, how long it lived and what caused its death.

What should the expert write if it cannot be established whether the baby breathed?

That it could not be determined, explaining the limits of the tests, without forcing a conclusion.

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Educational content on forensic and legal medicine; not legal advice and no substitute for the technical guides of Colombia's National Institute of Legal Medicine and Forensic Sciences. Laws change: each page links the official text and says when it was last checked. For a real case, follow the guide in force and ask the competent authority.

Sources: Micro-CT for the differentiation between live birth and stillbirth: A pilot study (Journal of Forensic Sciences (PMC), 2025); Stillbirth with a false-positive lung float test result - an unusual case report (Forensic Science, Medicine and Pathology (PMC), 2025); Lung aeration on post-mortem magnetic resonance imaging is a useful marker of live birth versus stillbirth (International Journal of Legal Medicine (PMC), 2015); A Case Report on an Intricate Forensic Dilemma: Precipitate Labor or Neonaticide? (Cureus (PMC), 2025); Decreto 786 de 1990: autopsias clínicas y médico-legales y viscerotomías (compilado en el Decreto 780 de 2016) (Función Pública, Gestor Normativo, 1990).

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