3.10 Core Ascertainment Variables

The first step in determining what core variables will be included in a surveillance programme is to define the goals and objectives of the congenital anomalies surveillance programme. Countries that already have a surveillance programme in place that includes the identification of populations at risk may consider including demographic variables such as maternal age, race and ethnicity, consanguinity, and other factors relevant to the local setting.

To facilitate data collection, countries can evaluate and summarize the availability of existing data sources (e.g. vital registries, and logbooks in hospital units), to determine what information regarding congenital anomalies is already being collected. Also, establishing the percentage of all births that are documented in vital registries, and determining whether the documentation includes only live births or both live births and fetal deaths, can be very useful.

After the list of core variables has been determined, these variables can then be incorporated into the methodology for case ascertainment. Table 3.3 lists core variables to be considered for inclusion in a congenital anomalies surveillance programme. Please refer to Appendix H for a list of core variables for consideration, and their definitions.

Table 3.3 Potential core ascertainment variables

Table 3.3 Potential core ascertainment variables


  • Case identification code
  • Date of report
  • Reporting hospital
  • City, province, state or territory
  • Name of person completing report

Identification information

  • Name: given name, family name
  • Date of birth or age
  • Race and ethnicity (if applicable)

Identification information

  • Name: given name, family name (including maiden name if appropriate)
  • Date of birth or age
  • Race and ethnicity (if applicable)
  • Address during the 3 months prior to pregnancy and the first trimester of pregnancy
  • Current address
  • Telephone number

Identification information

  • Name: given name, family name
  • Date of birth
  • Sex
  • Date of diagnosis
  • Birth outcome

Birth measurements

  • Gestational age (weeks)
  • Weight (g)
  • Length (cm)
  • Head circumference (cm)

Obstetric history

Total number of:

  • live births
  • stillbirths (fetal deaths)
  • spontaneous abortions
  • terminations of pregnancy

Birth information

  • Pregnancy outcome
  • Birth order, if multiple birth
  • Date of diagnosis
  • Date of death
  • Parental consanguinitya

Congenital anomaly/ anomalies present:

  • Type
  • Description:
    • detailed description of
      congenital anomaly
    • drawings or illustrations
      of congenital anomaly
  • Code
  • Diagnostic technique(s) (e.g. radiographs)
  • Photographs
Note: if a baby has more than one anomaly, any major congenital anomaly/anomalies are recorded first, followed by any other anomalies.

Autopsy results

  • Description
aConsanguinity has long been recognized as a significant factor in the occurrence of autosomal recessive diseases. However, its effect in the determination of single major congenital anomalies remains controversial. Even though some studies have shown variable degrees of association between consanguinity and non-syndromic neural tube defects, hydrocephalus and oral clefts, the majority are based on small numbers of individuals. In addition, differences in methodological approaches hinder comparisons between the different studies. The situation appears to be different for congenital heart defects, for which significant increases among the offspring of consanguineous couples have been identified in several multinational studies (15-21).

The following optional variables can be included if the surveillance programme in the country has the information available. See Appendix I for a listing of optional variables, and definitions for each.

Optional Variables


  • Source of information


  • occupation or work
  • family health history, environmental health history / form or occupational health form

Demographic Information

  • civil or marital status
  • occupation or work at time of conception
  • years and months residing in country
  • country identification number
  • weight (before pregnancy)
  • education (years or highest level)
  • religion (if applicable)
  • socioeconomic status

Birth information

  • Environmental health history / form or occupational health form
  • Type of delivery

Obstetric history

  • chronic diseases
  • date of last menstrual period
  • prenatal care, when it started, measure of adequacy
  • prenatal tests
  • family health history
  • medications or vaccines taken during pregnancy
  • any traditional medications commonly used