[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Epidemiology](https://durgical.com/en/epidemiology/) › [Public health indicators](https://durgical.com/en/epidemiology/areas/indicators/) › Infant, neonatal and perinatal mortality

# Infant, neonatal and perinatal mortality

- Measure

They count deaths of babies and young children per 1,000 live births. They are among the most sensitive indicators of living conditions and of care.

Updated Nov 5, 2026

## Key points

- Infant = deaths under 1 year / live births in the period × 1,000.
- Neonatal: under 28 days; post-neonatal: 28 days to under 1 year; neonatal + post-neonatal = infant.
- The denominator is live births, not the population under one year: strictly it is a ratio.
- Perinatal adds late fetal deaths and deaths in the first week; its denominator includes live births and fetal deaths.
- Neonatal causes depend mostly on pregnancy and birth care; post-neonatal causes depend more on the environment (infections, nutrition).

On this page

- The basics Key points
- What it is
- Formula and reading
- Worked example
- Age windows and denominators
- Markers
- How to read it
- Common pitfalls
- Memory aid
- Elsewhere in DurgiPedia

- Study Test yourself

- Connections Connections

## What it is

Infant mortality counts deaths before the first birthday per 1,000 live births in the same period. It splits into neonatal (under 28 days) and post-neonatal (28 days to under one year). Perinatal mortality joins late fetal deaths with deaths in the first week of life, and under-five mortality widens the window. Together they reflect both pregnancy and birth care and the conditions at home.

## Formula and reading

- Neonatal = deaths at 0 to 27 days / live births × 1,000.
- Post-neonatal = deaths at 28 days to 11 months / live births × 1,000.
- Perinatal = (late fetal deaths + deaths in the first 7 days) / (live births + late fetal deaths) × 1,000.
- Under five = deaths before the fifth birthday / live births × 1,000.
- The week cut-off for counting a fetal death varies between sources (22 or 28 weeks): check it before comparing.

## Worked example

- A made-up municipality records 2,500 live births and 15 late fetal deaths in a year.
- Infant deaths: 20 before 28 days (14 of them in the first week) and 10 between 28 days and one year.
- Neonatal: 20 / 2,500 × 1,000 = 8.0; post-neonatal: 10 / 2,500 × 1,000 = 4.0 per 1,000 live births.
- Infant: (20 + 10) / 2,500 × 1,000 = 12.0 per 1,000 live births; two thirds are neonatal.
- Perinatal: (15 + 14) / (2,500 + 15) = 29 / 2,515 = 0.0115; × 1,000 = 11.5 per 1,000 births (rounded).
- There were also 6 deaths between ages 1 and 4: under five = (30 + 6) / 2,500 × 1,000 = 14.4 per 1,000 live births.
- Reading: most of the burden is in the first month, so improvement should focus on antenatal care, birth and the newborn.

## Age windows and denominators

| Indicator | Deaths counted | Denominator | Per |
| --- | --- | --- | --- |
| Neonatal | From 0 to 27 days | Live births | 1,000 |
| Post-neonatal | From 28 days to under 1 year | Live births | 1,000 |
| Infant | Before 1 year | Live births | 1,000 |
| Perinatal | Late fetal deaths and deaths at 0 to 6 days | Live births plus fetal deaths | 1,000 births |
| Under five | Before the fifth birthday | Live births | 1,000 |

## Markers

- IMR
- Neonatal
- Post-neonatal
- Perinatal
- Under five
- × 1,000 LB

## How to read it

- In Colombia, the INS (national health institute) runs case reviews of perinatal and late neonatal deaths as part of public health surveillance.
- Gaps in infant mortality between regions and social groups are a direct way to measure health inequity.

## Common pitfalls

- Using the population under one year as the denominator instead of live births.
- Comparing perinatal rates calculated with different week cut-offs.
- Forgetting under-registration: in remote rural areas births and deaths go missing and the rate comes out falsely low.

## Memory aid

‘28 and 365’: up to 28 days is neonatal, up to a year is infant; all are divided by those born alive.

## Test yourself

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

## What is the denominator of the infant mortality rate?

Live births in the same period, multiplied by 1,000.

## What age window does neonatal mortality cover?

From birth until before 28 days of age.

## With 4,000 live births, 24 neonatal and 12 post-neonatal deaths, what is the infant mortality rate?

(24 + 12) / 4,000 × 1,000 = 9 per 1,000 live births.

## Why does the perinatal denominator include fetal deaths?

Because its numerator counts late fetal deaths; the denominator must cover everyone who could appear in the numerator: live births and fetal deaths.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/epidemiology/infant-neonatal-and-perinatal-mortality/)

## Elsewhere in DurgiPedia

- [Prematurity and fetal growth restriction](https://durgical.com/en/general-pathology/prematurity-and-fetal-growth-restriction/)

## Connections

## Related 5

- [Mortality rates: crude and specific](https://durgical.com/en/epidemiology/mortality-rates-crude-and-specific/)
- [Maternal mortality ratio](https://durgical.com/en/epidemiology/maternal-mortality-ratio/)
- [Social determinants of health](https://durgical.com/en/epidemiology/social-determinants-of-health/)
- [Life expectancy](https://durgical.com/en/epidemiology/life-expectancy/)
- [Comprehensive health care pathways (RIAS)](https://durgical.com/en/epidemiology/comprehensive-health-care-pathways/)

## Related conditions 2

- [Prematurity and its complications](https://durgical.com/en/conditions/prematurity-and-its-complications/)
- [Neonatal sepsis](https://durgical.com/en/conditions/neonatal-sepsis/)

[← All of epidemiology](https://durgical.com/en/epidemiology/)

Educational content on epidemiological and statistical methods; the examples use made-up numbers to teach the calculation. Not a clinical or legal guide: current Colombian rules are in the official sources.

Sources: [Principles of Epidemiology | Lesson 3 - Section 3](https://archive.cdc.gov/www_cdc_gov/csels/dsepd/ss1978/lesson3/section3.html) (Centers for Disease Control and Prevention, 2012); [Stillbirth](https://www.who.int/health-topics/stillbirth) (World Health Organization, 2026); [Lineamientos nacionales para la vigilancia en salud pública 2026 (vigilancia basada en eventos predefinidos)](https://www.ins.gov.co/BibliotecaDigital/lineamientos-nacionales-2026-fe-de-erratas.pdf) (Instituto Nacional de Salud (INS), Colombia, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/epidemiology/infant-neonatal-and-perinatal-mortality/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/epidemiology/infant-neonatal-and-perinatal-mortality/