A number of measures have been found to be effective in preventing SIDS including changing the sleeping position, breastfeeding, limiting soft bedding, immunizing the infant and using pacifiers. The use of electronic monitors has not been found to be useful as a preventative strategy. The effect that fans might have on the risk of SIDS has not been studied well enough to make any recommendation about them. Evidence regarding swaddling is unclear regarding SIDS. A 2016 review found tentative evidence that swaddling increases risk of SIDS, especially among babies placed on their stomachs or side while sleeping.

A large investigation into diphtheria-tetanus-pertussis vaccination and potential SIDS association by Berlin School of Public Health, Charité – Universitätsmedizin Berlin concluded: "Increased DTP immunisation coverage is associated with decreased SIDS mortality. Current recommendations on timely DTP immunisation should be emphasised to prevent not only specific infectious diseases but also potentially SIDS."

Many other studies have also reached conclusions that vaccinations reduce the risk of SIDS. Studies generally show that SIDS risk is approximately halved by vaccinations.

Preterm birth is the most common cause of perinatal mortality, causing almost 30 percent of neonatal deaths. Infant respiratory distress syndrome, in turn, is the leading cause of death in preterm infants, affecting about 1% of newborn infants. Birth defects cause about 21 percent of neonatal death.

Early neonatal mortality refers to a death of a live-born baby within the first seven days of life, while late neonatal mortality covers the time after 7 days until before 28 days. The sum of these two represents the neonatal mortality. Some definitions of the PNM include only the early neonatal mortality. Neonatal mortality is affected by the quality of in-hospital care for the neonate. Neonatal mortality and postneonatal mortality (covering the remaining 11 months of the first year of life) are reflected in the Infant Mortality Rate.

Administration of oxygen at 15 litres per minute by face mask or bag valve mask is often sufficient, but tracheal intubation with mechanical ventilation may be necessary. Suctioning of pulmonary oedema fluid should be balanced against the need for oxygenation. The target of ventilation is to achieve 92% to 96% arterial saturation and adequate chest rise. Positive end-expiratory pressure will generally improve oxygenation. Drug administration via peripheral veins is preferred over endotracheal administration. Hypotension remaining after oxygenation may be treated by rapid crystalloid infusion. Cardiac arrest in drowning usually presents as asystole or pulseless electrical activity. Ventricular fibrillation is more likely to be associated with complications of pre-existing coronary artery disease, severe hypothermia, or the use of epinephrine or norepinephrine.

Most drowning is preventable. It has been estimated that more than 85% of drownings could have been prevented by supervision, training in water skills, technology, regulation and public education.

Respiratory stimulants such as nikethamide were traditionally used to counteract respiratory depression from CNS depressant overdose, but offered limited effectiveness. A new respiratory stimulant drug called BIMU8 is being investigated which seems to be significantly more effective and may be useful for counteracting the respiratory depression produced by opiates and similar drugs without offsetting their therapeutic effects.

If the respiratory depression occurs from opioid overdose, usually an opioid antagonist, most likely naloxone, will be administered. This will rapidly reverse the respiratory depression unless complicated by other depressants. However an opioid antagonist may also precipitate an opioid withdrawal syndrome in chronic users.

The Lazarus phenomenon raises ethical issues for physicians, who must determine when medical death has occurred, resuscitation efforts should end, and postmortem procedures such as autopsies and organ harvesting may take place.

Medical literature has recommended observation of a patient's vital signs for five to ten minutes after cessation of resuscitation before certifying death.

As a side effect of medicines or recreational drugs, hypoventilation may become potentially life-threatening. Many different central nervous system (CNS) depressant drugs such as ethanol, benzodiazepines, barbiturates, GHB, sedatives and opioids produce respiratory depression when taken in large or excessive doses, or mixed with other depressants. Strong opiates (such as fentanyl, heroin, or morphine), barbiturates, and certain benzodiazepines (short acting ones and alprazolam) are known for depressing respiration. In an overdose, an individual may cease breathing entirely (go into respiratory arrest) which is rapidly fatal without treatment. Opioids, in overdose or combined with other depressants, are notorious for such fatalities.

Suicides using bags or masks and gases are well documented in the literature.

Suicide bags have been used with gases other than inert gases, with varying outcomes. Examples of other gases are propane-butane and natural gas.

Suicides using a suicide bag and an inert gas produce no characteristic post-mortem macroscopic or microscopic findings. Forensic death investigations of cause and manner of death may be very difficult when people commit suicide in this manner, especially if the apparatus (such as the bag, tank, or tube) is removed by someone after the death. Petechiae, which are often considered a marker of asphyxia, are present in only a small minority of cases (3%). Frost reported that of the two cases he studied that featured death from inert gas asphyxiation using a suicide bag, one had "bilateral eyelid petechiae and large amounts of gastric content in the airways and that these findings challenge the assumption that death by this method is painless and without air hunger, as asserted in "Final Exit"." A review study by Ely and Hirsch (2000) concludes that conjunctival and facial petechiae are the product of purely mechanical vascular phenomena, unrelated to asphyxia or hypoxia, and do not occur unless ligatures were also found around the neck. The authors wrote,

There are also documented cases of suicide attempts using the suicide bag that failed. A case report study in 2015 discussed the risks associated with failed attempts using this method. The authors wrote, "If the process is interrupted by someone, there is no gas or the tube slips out of the bag, there is a high risk of severe hypoxia of the central nervous system."

Promoters of this suicide method recommend it to terminally ill patients. However, across the world, most people who use suicide bags are physically healthy. Instead of having incurable cancer or other life-threatening physical diseases, most of the users have psychiatric disorders or substance abuse problems that might possibly be addressed through medical and psychological treatment. The demographics of its users varies; in one survey, the method had been used mostly by middle-aged adults in failing health, who were attracted to the relative nonviolence of the method.

This suicide method is also typically used by younger or middle-aged adults, rather than by older adults. In the US, it is more commonly chosen by non-Hispanic white males than by women or people of other races.

Lazarus syndrome, (the Lazarus heart) also known as autoresuscitation after failed cardiopulmonary resuscitation, is the spontaneous return of circulation after failed attempts at resuscitation. Its occurrence has been noted in medical literature at least 38 times since 1982. It takes its name from Lazarus who, as described in the New Testament of The Bible, was raised from the dead by Jesus.

Occurrences of the syndrome are extremely rare and the causes are not well understood. One hypothesis for the phenomenon is that a chief factor (though not the only one) is the buildup of pressure in the chest as a result of cardiopulmonary resuscitation (CPR). The relaxation of pressure after resuscitation efforts have ended is thought to allow the heart to expand, triggering the heart's electrical impulses and restarting the heartbeat. Other possible factors are hyperkalemia or high doses of epinephrine.

Brainstem death is a clinical syndrome defined by the absence of reflexes with pathways through the brainstem—the “stalk” of the brain, which connects the spinal cord to the mid-brain, cerebellum and cerebral hemispheres—in a deeply comatose, ventilator-dependent patient.

Identification of this state carries a very grave prognosis for survival; cessation of heartbeat often occurs within a few days although it may continue for weeks or even months if intensive support is maintained.

In the United Kingdom, the formal diagnosis of brainstem death by the procedure laid down in the official Code of Practice permits the diagnosis and certification of death on the premise that a person is dead when consciousness and the ability to breathe are permanently lost, regardless of continuing life in the body and parts of the brain, and that death of the brainstem alone is sufficient to produce this state.

This concept of brainstem death is also accepted as grounds for pronouncing death for legal purposes in India and Trinidad & Tobago. Elsewhere in the world the concept upon which the certification of death on neurological grounds is based is that of permanent cessation of all function in all parts of the brain—whole brain death—with which the reductionist United Kingdom concept should not be confused. The United States' President's Council on Bioethics made it clear, in its White Paper of December 2008, that the United Kingdom concept and clinical criteria are not considered sufficient for the diagnosis of death in the United States of America.

The United Kingdom (UK) criteria were first published by the Conference of Medical Royal Colleges (with advice from the Transplant Advisory Panel) in 1976, as prognostic guidelines. They were drafted in response to a perceived need for guidance in the management of deeply comatose patients with severe brain damage who were being kept alive by mechanical ventilators but showing no signs of recovery. The Conference sought “to establish diagnostic criteria of such rigour that on their fulfilment the mechanical ventilator can be switched off, in the secure knowledge that there is no possible chance of recovery”. The published criteria—negative responses to bedside tests of some reflexes with pathways through the brainstem and a specified challenge to the brainstem respiratory centre, with caveats about exclusion of endocrine influences, metabolic factors and drug effects—were held to be “sufficient to distinguish between those patients who retain the functional capacity to have a chance of even partial recovery and those where no such possibility exists”. Recognition of that state required the withdrawal of fruitless further artificial support so that death might be allowed to occur, thus “sparing relatives from the further emotional trauma of sterile hope”.

In 1979, the Conference of Medical Royal Colleges promulgated its conclusion that identification of the state defined by those same criteria—then thought sufficient for a diagnosis of brain death—“means that the patient is dead” Death certification on those criteria has continued in the United Kingdom (where there is no statutory legal definition of death) since that time, particularly for organ transplantation purposes, although the conceptual basis for that use has changed.

In 1995, after a review by a Working Group of the Royal College of Physicians of London, the Conference of Medical Royal Colleges formally adopted the “more correct” term for the syndrome, "brainstem death"—championed by Pallis in a set of 1982 articles in the British Medical Journal —and advanced a new definition of human death as the basis for equating this syndrome with the death of the person. The suggested new definition of death was the “irreversible loss of the capacity for consciousness, combined with irreversible loss of the capacity to breathe”. It was stated that the irreversible cessation of brainstem function will produce this state and “therefore brainstem death is equivalent to the death of the individual”.

Pallor mortis results from the cessation of capillary circulation throughout the body. Gravity then causes the blood to sink down into the lower parts of the body, creating livor mortis.

Pallor mortis occurs almost immediately (within 15–25 minutes) post-mortem; paleness develops so rapidly after death that it has little to no use in determining the time of death, aside from saying that it either happened less than 30 minutes ago or more, which could help if the body were found very soon after death.

The lack of generally recognized clinical recommendations available are a reflection of the dearth of data on the effectiveness of any particular clinical strategy, but on the basis of present evidence, the following may be relevant:

- Epileptic seizure control with the appropriate use of medication and lifestyle counseling is the focus of prevention.

- Reduction of stress, participation in physical exercises, and night supervision might minimize the risk of SUDEP.

- Knowledge of how to perform the appropriate first-aid responses to seizure by persons who live with epileptic people may prevent death.

- People associated with arrhythmias during seizures should be submitted to extensive cardiac investigation with a view to determining the indication for on-demand cardiac pacing.

- Successful epilepsy surgery may reduce the risk of SUDEP, but this depends on the outcome in terms of seizure control.

- The use of anti suffocation pillows have been advocated by some practitioners to improve respiration while sleeping, but their effectiveness remain unproven because experimental studies are lacking.

- Providing information to individuals and relatives about SUDEP is beneficial.

Marine-derived omega-3 polyunsaturated fatty acids (PUFAs) has been promoted for the prevention of sudden cardiac death due to its postulated ability to lower triglyceride levels, prevent arrhythmias, decrease platelet aggregation, and lower blood pressure. However, according to a recent systematic review, omega-3 PUFA supplementation are not being associated with a lower risk of sudden cardiac death.

There is no cure or standard treatment for anencephaly and the prognosis for patients is death. Most anencephalic fetuses do not survive birth, accounting for 55% of non-aborted cases. Infants that are not stillborn will usually die within a few hours or days after birth from cardiorespiratory arrest.

Four recorded cases of anencephalic children surviving for longer periods of time are Stephanie Keene (better known as Baby K) of Falls Church, Virginia, USA, who lived for 2 years 174 days; Vitoria de Cristo, born in Brazil in January 2010 and surviving until July 17, 2012; Nickolas Coke of Pueblo, Colorado, USA, who lived for 3 years and 11 months, and died October 31, 2012; and Angela Morales, from Providence, Rhode Island, who live for 3 years and 9 months, and died December 16 2017.

In almost all cases, anencephalic infants are not aggressively resuscitated because there is no chance of the infant's ever achieving a conscious existence. Instead, the usual clinical practice is to offer hydration, nutrition, and comfort measures and to "let nature take its course". Artificial ventilation, surgery (to fix any co-existing congenital defects), and drug therapy (such as antibiotics) are usually regarded as futile efforts. Some clinicians and medical ethicists view even the provision of nutrition and hydration as medically futile.

An implantable cardioverter defibrillator (ICD) is a battery powered device that monitors electrical activity in the heart and when an arrhythmia or asystole is detected is able to deliver an electrical shock to terminate the abnormal rhythm. ICDs are used to prevent sudden cardiac death (SCD) in those that have survived a prior episode of sudden cardiac arrest (SCA) due to ventricular fibrillation or ventricular tachycardia (secondary prevention). ICDs are also used prophylactically to prevent sudden cardiac death in certain high risk patient populations (primary prevention).

Numerous studies have been conducted on the use of ICDs for the secondary prevention of SCD. These studies have shown improved survival with ICDs compared to the use of anti-arrhythmic drugs. ICD therapy is associated with a 50% relative risk reduction in death caused by an arrhythmia and a 25% relative risk reduction in all cause mortality.

Primary prevention of SCD with ICD therapy for high risk patient populations has similarly shown improved survival rates in a number of large studies. The high risk patient populations in these studies were defined as those with severe ischemic cardiomyopathy (determined by a reduced left ventricular ejection fraction (LVEF)). The LVEF criteria used in these trials ranged from less than or equal to 30% in MADIT-II to less than or equal to 40% in MUSTT.

Brain death is the complete loss of brain function (including involuntary activity necessary to sustain life). It differs from persistent vegetative state, in which the person is alive and some autonomic functions remain.

Brain death is used as an indicator of legal death in many jurisdictions, but it is defined inconsistently. Various parts of the brain may keep functioning when others do not anymore, and the term "brain death" has been used to refer to various combinations. For example, although a major medical dictionary says that "brain death" is synonymous with "cerebral death" (death of the cerebrum), the US National Library of Medicine Medical Subject Headings (MeSH) system defines brain death as including the brainstem. The distinctions can be important because, for example, in someone with a dead cerebrum but a living brainstem, the heartbeat and ventilation can continue unaided, whereas in whole-brain death (which includes brain stem death), only life support equipment would keep those functions going. Patients classified as brain-dead can have their organs surgically removed for organ donation.

Yunnan sudden death syndrome is a label used to define unexplained cases of cardiac arrest, which afflicted significant numbers of rural villagers in Yunnan province, in southwest China. Cases occurred almost always during the midsummer rainy season (from June to August), at an altitude of . The cause turned out to be a mushroom now blamed for an estimated 400 deaths in the past three decades.

The mysterious fatalities were recorded for decades before researchers from the Chinese Center for Disease Control and Prevention isolated a significant factor common in every case: a tiny unknown mushroom which was unintentionally gathered and consumed during wild mushroom harvests in the region. Previously the syndrome was thought to be caused by Keshan disease, caused by the Coxsackie virus.

The mushroom, "Trogia venenata", is also known as 'Little White'. It has been determined that families collecting fungi to sell have been eating these Little White mushrooms as they have no commercial value. Three amino acids present in the mushrooms have been shown to be toxic. The mushrooms have also been shown to contain very high quantities of barium, and it may be that some of the deaths are simply from barium poisoning.

In the hours before death, about two-thirds of the victims had such symptoms as nausea, dizziness, heart palpitations, seizures and fatigue.

However, in December 2012 it was announced that Dr Xu Jianping (徐建平) has been collecting samples of "Trogia venenata" in Yunnan for the past three years, and his research now shows that barium levels in the wild mushroom are no higher than those of common foods such as poultry and fish. Nonetheless, it appears the mushroom will still likely play a role. Since publication of the widely circulated 2010 "Science" article, no instances of Yunnan sudden death syndrome have been reported.

The cause of anencephaly is disputed by medical professionals and researchers.

Folic acid has been shown to be important in neural tube formation since at least 1995, and as a subtype of neural tube defect, folic acid may play a role in anencephaly. Studies have shown that the addition of folic acid to the diet of women of child-bearing age may significantly reduce, although not eliminate, the incidence of neural tube defects. Therefore, it is recommended that all women of child-bearing age consume 0.4 mg of folic acid daily, especially those attempting to conceive or who may possibly conceive, as this can reduce the risk to 0.03%. It is not advisable to wait until pregnancy has begun, since, by the time a woman knows she is pregnant, the critical time for the formation of a neural tube defect has usually already passed. A physician may prescribe even higher dosages of folic acid (5 mg/day) for women having had a previous pregnancy with a neural tube defect.

In general, neural tube defects do not follow direct patterns of heredity, though there is some indirect evidence of inheritance, and recent animal models indicate a possible association with deficiencies of the transcription factor TEAD2. Studies show that a woman who has had one child with a neural tube defect such as anencephaly has about a 3% risk of having another child with a neural tube defect, as opposed to the background rate of 0.1% occurrence in the population at large. Genetic counseling is usually offered to women at a higher risk of having a child with a neural tube defect to discuss available testing.

It is known that people taking certain anticonvulsants and people with insulin-dependent diabetes have a higher risk of having a child with a neural tube defect.

Sudden unexpected death in epilepsy (SUDEP) is a fatal complication of epilepsy. It is defined as the sudden and unexpected, non-traumatic and non-drowning death of a person with epilepsy, without a toxicological or anatomical cause of death detected during the post-mortem examination.

While the mechanisms underlying SUDEP are still poorly understood, it is possibly the most common cause of death as a result of complications from epilepsy, accounting for between 7.5 and 17% of all epilepsy-related deaths and 50% of all deaths in refractory epilepsy. The causes of SUDEP seem to be multifactorial and include respiratory, cardiac and cerebral factors, as well as the severity of epilepsy and seizures. Proposed pathophysiological mechanisms include seizure-induced cardiac and respiratory arrests.

SUDEP occurs in about 1 in 1,000 adults and 1 in 4,500 children with epilepsy a year. Rates of death as a result of prolonged seizures (status epilepticus) are not classified as SUDEP.

While the diagnosis of brain death has become accepted as a basis for the certification of death for legal purposes, it should be clearly understood that it is a very different state from biological death - the state universally recognized and understood as death. The continuing function of vital organs in the bodies of those diagnosed brain dead, if mechanical ventilation and other life-support measures are continued, provides optimal opportunities for their transplantation.

When mechanical ventilation is used to support the body of a brain dead organ donor pending a transplant into an organ recipient, the donor's date of death is listed as the date that brain death was diagnosed.

In some countries (for instance, Spain, Finland, Poland, Wales, Portugal, and France), everyone is automatically an organ donor after diagnosis of death on legally accepted criteria, although some jurisdictions (such as Singapore, Spain, Wales, France, Czech Republic and Portugal) allow opting out of the system. Elsewhere, consent from family members or next-of-kin may be required for organ donation. In New Zealand, Australia, the United Kingdom (excluding Wales) and most states in the United States, drivers are asked upon application if they wish to be registered as an organ donor.

In the United States, if the patient is at or near death, the hospital must notify a transplant organization of the person's details and maintain the patient while the patient is being evaluated for suitability as a donor. The patient is kept on ventilator support until the organs have been surgically removed. If the patient has indicated in an advance health care directive that they do not wish to receive mechanical ventilation or has specified a do not resuscitate order and the patient has also indicated that they wish to donate their organs, some vital organs such as the heart and lungs may not be able to be recovered.