Revision as of 16:17, 13 November 2006

410

The mortality of live-born children who have not yet reached their first birthday is called infant mortality ¹. The mortality of live-born children who die before reaching a certain age taken as four weeks or 28 days, the so-called neo-natal period ³, is called neo-natal mortality ². The mortality during the first week of life is called early neo-natal mortality ⁴. The term post-neonatal mortality ⁵ refers to deaths after the neo-natal period, but before reaching the age of one year.

• 3. In certain statistics the neo-natal period is defined as the first month of life. The term early infancy is occasionally used as an approximate equivalent to the neo-natal period, as, e.g., in "diseases of early infancy."

411

The expression foetal mortality ¹ is used for deaths prior to the complete expulsion or extraction from its mother of a product of conception (602-6) irrespective of the duration of pregnancy (603-3). The terms intra-uterine mortality ¹ or mortality in utero ¹ may also be used. The corresponding deaths are called foetal deaths ² or intra-uterine deaths ². Early foetal mortality ³ occurs before the twentieth week of gestational life, while intermediate foetal mortality ⁴ occurs between the twentieth and the 28th week of gestation. After the twenty-eighth week, one refers to late foetal mortality ⁵ and the product is called a late foetal death ⁵ or, popularly, a stillbirth ⁵. Perinatal mortality ⁶ includes late foetal mortality and a portion of infant mortality that may include either early neo-natal deaths, or all neo-natal deaths.

• 1. Foetal - also spelled fetal.
• 2. Also designated as pregnancy wastage. These terms include abortions (603-5), miscarriages (604-1) and stillbirths.
• 3. Early foetal deaths are also popularly known as miscarriages.
• 5. Stillbirth, n. - stillborn, adj. In certain countries, including France, children born alive who died before registration may be legally included among the stillborn, and are called false stillbirths.
• 6. The corresponding deaths are called perinatal deaths.

412

The ratios of deaths under one year of age ¹, of deaths of less than 28 days, and of deaths of less than one week, occurring in a year, to the number of live births of the same year give respectively the infant mortality rate ², the neo-natal mortality rate ³ and the early neo-natal mortality rate ⁴. These rates are generally expressed per one thousand live births. When deaths are cross-classified by age and year of birth, it is possible to divide the deaths under one year by the births in the two cohorts to which they belong. The resulting index is an adjusted infant mortality rate ⁵ equivalent to a probability of dying before age one ⁵. In the absence of such information separation factors ⁶ may be estimated, which divide infant deaths into those occurring to infants born in the current calendar year and to infants born in the previous calendar year.

413

The proportion of late foetal deaths (411-5) among all births is called a late foetal mortality rate ¹. The ratio of late foetal deaths to live births (601-4) is called a late foetal mortality ratio ². A foetal mortality rate ³ represents the number of known intra-uterine deaths per one thousand births in the same year while the foetal mortality ratio ⁴ is the ratio of intra-uterine deaths to live births in a given year. These indices greatly understate intra-uterine mortality since early intra-uterine deaths frequently remain unobserved or unknown. A better measurement of intra-uterine mortality is provided by intra-uterine mortality tables ⁵, a specialized application of the life table (cf. 432-) which takes into account the duration of gestation. The perinatal mortality rate ⁶ relates perinatal deaths (411-6*) to the sum of late foetal deaths and live births.

• 1. Also called stillbirth rate. This usage is not recommended.
• 2. Also called stillbirth ratio. This usage is not recommended.
• 6. The perinatal mortality ratio relates perinatal deaths to live births only.

414

In the study of age-specific mortality ¹, the terms infant mortality (410-2) and neo-natal mortality (410-3) refer to generally accepted time periods. The usage of such terms as child mortality ², adult mortality ⁴ or mortality of old age ⁵ is not uniform. Post-infantile child death rate ⁶ sometimes refers to the death rate between one and 4 years of age.