Add to "My indicators"
Prevalence of neural tube defects
This indicators assesses the rate of births in the population that result in neural tube defects.
Spina bifida, anencephaly and other similar conditions are collectively called neural tube defects (NTDs). They result from improper closure of the spinal cord and cranium and are common congenital anomalies associated with folate insufficiency (1). NTDs constitute a heterogeneous group of disorders that occur during the first weeks of gestation, involving specific elements of the neural tube and its derivatives. The birth prevalence of NTDs in the general population varies between countries (2, 3). A main justification for fortification of wheat or maize flour with folic acid is to prevent NTDs.
In birth defects epidemiology, the terms live birth prevalence, birth prevalence and total prevalence are used:
• Live birth prevalence of congenital anomalies: measures the number of cases with congenital anomalies among live births and is defined as the number of live births with any congenital anomaly (numerator) among a defined cohort of live births (denominator).
• Birth prevalence of congenital anomalies: measures the number of cases with congenital anomalies among live births and fetal deaths (stillbirths), and is defined as the number of live births and fetal deaths (stillbirths) with any congenital anomaly (numerator) among a defined cohort of live births plus fetal deaths (stillbirths) (denominator).
• Total prevalence of congenital anomalies: measures the number of cases with congenital anomalies in live births, fetal deaths (stillbirths), plus elective terminations of pregnancy for fetal anomaly, and is defined as the number of cases of live births, fetal deaths (stillbirths) and elective terminations of pregnancy for fetal anomaly (numerator) among a defined cohort of live births, fetal deaths (stillbirths) and elective terminations (denominator).
The birth prevalence of NTDs is usually expressed per 1000 or per 10 000 births. Divide the numerator by the denominator. Multiply the result by 1000 to express the results per 1000. Alternatively, the results can be multiplied by 10 000 to express the results per 10 000.
• Divide the numerator by the denominator. Multiply the result by 100 to convert the number into a percentage.
Considerations for calculations:
• If elective terminations and stillbirths are recorded, these can be included in the denominator in addition to live births. Terminations and stillbirths with a diagnosis of NTD can be included in the numerator.
• Further, depending on what information is available, the birth prevalence of NTDs can be expressed in many ways to reflect the inclusion criteria for the indicator: per live births; per live births and stillbirths; per live births, stillbirths and elective terminations. It is important to accurately define the inclusion criteria when reporting the results of this indicator.
• Population-based congenital anomalies surveillance programmes capture birth outcomes with NTDs that occur among a population that is resident in a defined geographical area. Hospital- or facility-based congenital anomalies surveillance programmes capture birth outcomes with NTDs that occur in selected facilities.
• Sentinel congenital anomalies surveillance programmes are generally set up in one or a few facilities/hospitals, to obtain rapid estimates of the occurrence of an adverse birth outcome.
anencephaly, birth defects, congenital anomalies, folate, folic acid, neural tube defects, spina bifida
All
Outcome
Decreased morbidity and mortality, Improved development
0-5 months, 6-11 months, Women of reproductive age
None,
Folate, Vitamin B6
Community, Health systems, Market-based
Recent data regarding the prevalence of NTDs in low- and middle-income countries may be difficult to collect.
For collection of data to estimate the birth prevalence of NTDs, note whether the cases are identified from live births, stillbirths, and/or pregnancies that are electively terminated after prenatal diagnosis of a NTD (after 20 weeks of gestation), and include the description of the birth outcome in the numerator. The denominator should have the same birth attributes as the numerator.
This information is relatively easy and feasible to calculate from birth registry and other surveillance data when it is routinely collected in countries.
Surveillance of congenital anomalies should be ongoing and should involve a systematic review of birth outcomes to determine the presence of congenital anomalies (1).
Surveillance programmes can be population based or hospital/facility based and can use active or passive case ascertainment, or can be a hybrid of the two.
In addition to maternal folate intake, there may be other nutritional and non-nutritional factors that influence the prevention of NTDs (2).
This information may be difficult to collect or not available in many countries.
A country established an information system that registers all live births and any congenital anomalies present at birth. Staff used the World Health Organization (WHO) International Classification of Diseases (ICD-10) to identify infants with spina bifida (code Q05 (4, 5)). In a 12-month period, 634 cases of spina bifida were observed in a total of 2 747 277 live births.
Numerator: 634 spina bifida cases
Denominator: 2 747 277 live births
Calculation: 634/2 747 277 * 10 000 = spina bifida birth prevalence of 2.31/10 000 live births.
1. WHO/CDC/ICBDSR. Birth defects surveillance: a manual for programme managers. Geneva: World Health Organization; 2014 ( http://apps.who.int/iris/bitstream/10665/110223/1/9789241548724_eng.pdf?ua=1&ua=1, accessed 12 October 2015).
2. Bhutta ZA, Hasan B. Periconceptional supplementation with folate and/or multivitamins for preventing neural tube defects: RHL commentary (last revised: 7 January 2002). The WHO Reproductive Health Library; Geneva: World Health Organization; 2002 (http://apps.who.int/rhl/pregnancy_childbirth/antenatal_care/nutrition/bhcom/en/, accessed 6 October 2015).
3. Lo A Lo A, Polsek D, Sidhu S. Estimating the burden of neural tube defects in low- and middle income countries. J Glob Health. 2014;4:010402. doi:10.7189/jogh.04.010402.
4. International statistical classification of diseases and related health problems, 10th revision. Geneva: World Health Organization; 2016 (http://apps.who.int/classifications/icd10/browse/2016/en, accessed 6 October 2015).
5. International statistical classification of diseases and related health problems, 10th revision [online database]. Geneva; World Health Organization; 2010 (http://apps.who.int/classifications/icd10/browse/2010/en, accessed 03 August 2014).