The Fertility data at national level are based on the annual demographic data collection in the field of demography carried out by Eurostat. The completeness of information depends on the availability of data reported by the National Statistical Institutes.

The first demographic data collection of each year (T), named Rapid, is carried out in April-May (deadline 15 May of year T); during this data collection the first results on the main demographic developments in the previous year and the population on 1 January of the current year are collected from the national statistical institutes.

The Joint demographic data collection is carried out in cooperation with United Nation Statistical Division (UNSD) in the summer of each year, having the deadline 15 September. During this data collection Eurostat collects from the national statistical institutes detailed data by sex, age and other characteristics for the demographic events (births, deaths, marriages and divorces) of the previous year and the population on 1 January of the current and previous years.

The Nowcast demographic data collection is carried out in October-November (deadline 15 November of year T). The monthly time series on births, deaths, immigrants and emigrants available from the beginning of current year T are collected, with the purpose of producing a forecast on 1 January population of the following year (T+1).

More specifically, during year T the following data are collected and disseminated on fertility field:

- Total live births in year (T-1)

- Live births by month in year T

- Live births by mother's age, year of birth and legal marital status in year T-1

The most recent (aggregated) data on live births includes also the most recent Eurostat now casts on the demographic indicators (published in December of each year). In principle, the demographic balance is updated three times per year, after each of the national data collections.

Detailed information on fertility (by age, sex and marital status, birth order, educational attainment) are updated towards the end of each year based on information collected during the Joint data collection.

Moreover, any update sent by the countries in-between data collections are validated, processed and uploaded into Eurostat's demographic database and in Eurostat's free dissemination online database as soon as possible. Aggregates are recalculated accordingly.

The data transmitted by the National Statistical Institutes are validated by Eurostat, processed and uploaded into Eurostat's Demographic Database and in Eurostat's free dissemination online database. The data are also disseminated in several thematic and horizontal Eurostat's publications.

Live births: Births of children that showed any sign of life. It is the number of births excluding stillbirths (total births include live births and stillbirths).

Stillbirth: The expulsion or extraction from the mother of a dead foetus after the time at which it would normally be resumed capable of independent extrauterine existence (commonly taken to be after 24 to 28 weeks of gestation).

Crude birth rate: The ratio of the number of live births during the year to the total population in that year. The value is expressed per 1000 inhabitants.

Mean age of women at childbirth: The mean age of women when their children are born.

Total fertility rate: The mean number of children that would be born alive to a woman during her lifetime if she were to pass through her childbearing years conforming to the fertility rates by age of a given year.

Fertility rates by mother's age (age specific fertility rate): The number of births to mothers of age x to the average female population of age x.

Age concept:

Most National Statistical Institutes of the EU Member States provide data on the number of live births by both dimensions: mother's age and mothr's year of birth. Live births are compiled and disseminated, based on the data collected, as follows: by mother's age at last birthday (also referred as age completed) and by mother's age reached during the year. The availability of data on live births by the two concepts among the countries starts at different moment of time series.

Eurostat uses the concept of age completed for the calculation of the fertility indicators.

Eurostat's general and cross-domains publications, yearbooks and pocketbooks.

'The social situation in the European Union' report and 'Demography report', in cooperation with DG-EMPL.

Two regular statistics in focus/data in focus publications on population and other demographic indicators:

- 'Population in Europe: first results': published in summer, containing the first demographic estimates on the demographic balance for the year T-1. The publication is based on the Rapid data collection.

- 'First demographic estimates' on the total population by country on 1 January of the following year (now casts), published at the end of the year.

Eurostat requests to all countries demographic statistics based on the concept of usual resident population. The statistics on population refer to the national and regional population at its usual residence. In accordance with this concept, the following persons are considered to be usually residents of the geographical area in question: those who have lived in their place of usual residence for a continuous period of at least 12 months before the reference date or those who arrived in their place of usual residence during the 12 months before the reference date with the intention of staying there for at least one year. Countries may provide however the legal or registered population instead of the usually resident population.

Eurostat requests from Member States and from other countries participating in the Eurostat annual demographic data collections, data on population on 1 January. Countries may collect data at national level using a different reference date: for most of them, 1 January or 31 December of the previous year is used but some countries may refer to mid-year or another date. However, population data on 1 January are estimated and transmitted to Eurostat. The population is based either on data from the most recent census, adjusted by the components of population change produced since the last census, or on population registers.

Absolute figures received from the National Statistical Institutes are validated by Eurostat before being dissemination in Eurostat's free dissemination online datanse.

Basic validations are carried out to check if the totals provided by the countries are consistent with the breakdown by sex, by year and by other characteristics (e.g., live births are the sum of births inside marriage plus births outside marriage; total population is equal to the sum of marital statuses, etc.).

Cross validations are carried out to check consistency between the different tables of one domain (e.g., the totals of births must be equal to the sum of births by rank).

Time series analysis by country can be done to check if outliers appear.

When demographic indicators are calculated, other errors can be detected in the time series by country and they are investigated.