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.
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.
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.
Elsewhere in DurgiPedia
Connections
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 (Centers for Disease Control and Prevention, 2012); Stillbirth (World Health Organization, 2026); Lineamientos nacionales para la vigilancia en salud pública 2026 (vigilancia basada en eventos predefinidos) (Instituto Nacional de Salud (INS), Colombia, 2026).
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Representative model, for educational purposes only.