Percent of women with night blindness in last pregnancy
The percent of women who reported night blindness during their last pregnancy that resulted in a live birth during a specified time period. The International Vitamin A Consultative Group [IVACG] recommends during
the past three years (IVACG, 2002). Christian (2002) found that Nepali women with live births were more likely to have reported night blindness than women with stillbirths and, to avoid underestimating prevalence, proposed eliciting the history of night blindness only from women whose last pregnancy ended in a live birth.
This indicator is calculated as:
(Number of women who had night blindness during last pregnancy / Total number of women with last pregnancy resulting in live birth during past 3 years) x 100
Maternal night blindness is the inability to see normally after dusk or at night during pregnancy, especially the last trimester and early postpartum. Night blindness is the most common ocular manifestation of moderate to severe Vitamin A deficiency (VAD) and is evidenced by delayed dark adaptation or difficulty seeing in dim light (IVACG, 2002). Evaluators need to distinguish and exclude from estimates of prevalence (both the numerator and denominator) women whose blindness was probably due to visual impairment from other causes.
Self-report of night blindness during last pregnancy that ended in a live birth. In areas where night blindness exists, qualitative research needs to be conducted to determine the local term or description of symptoms for night blindness in that area. Interviewers and surveys should use local terms for night blindness whenever possible and conduct interviews in a standard manner. Data can be disaggregated by age groups and parity and where available, by relevant socioeconomic and demographic factors such as education, income, and urban/rural residence.
Population based surveys (e.g., DHS, UNICEF-MICS); local and program-based studies
Maternal night blindness is an indicator of severe VAD. WHO has recommended that at least two biologic indicators (i.e., night blindness, biochemical, or histological) be used to determine if vitamin A deficiency (VAD) exists as a public health problem, rather than relying on a single indicator (Gorstein, 2007). Serum retinol and night blindness during pregnancy are the most likely biological indicators to be collected in cross-sectional surveys, such as, DHS. The common occurrence of night blindness and its relatively simple, reliable assessment make this a useful indicator of VAD in the community.
An estimated 10 percent of women in low-income regions of the world experience night blindness during pregnancy (West, 2002). A reported prevalence rate of night blindness among pregnant women of 5 percent or higher is considered a signal that VAD is a significant public health problem in a given population. The 5 percent cut-off was set higher than the potential false-positive prevalence (3%) to improve specificity (IVACG, 2002). This indicator relates to two of the Millennium Development Goals: #4. Reduce child mortality; and #5. Improve maternal health.
Information on the validity of the indicator comes mainly from a study of low-dose supplementation with vitamin A or B-carotene to women of reproductive age in Nepal (West et al., 1999). Supporting its validity as an indicator of maternal vitamin A status, night blindness in pregnancy was strongly associated with low retinol in serum and breast milk, abnormal conjunctival cytology, and impaired dark adaptation (Christian, 2002). Furthermore, the incidence of maternal night blindness was reduced by two-thirds with vitamin A interventions, providing evidence that the night blindness resulted from VAD (Christian, 2002).
Night blind women have considerably greater risks for morbidity and mortality than non-night blind women. In the Nepal study, pregnant women reporting night blindness were more likely to be anemic, ill, acutely undernourished and to be consuming a nutritionally poorer diet (Christian, 2002). Maternal night blindness was associated with a fourfold higher risk of all-cause mortality for up to two years following the night blindness (Christian, 2002). Because of health and survival risks associated with maternal night blindness, cases identified during antenatal care should be treated immediately.
A history of night blindness is relatively easy to obtain when a local term exists for the condition, but interviewers should ask questions concerning the history in a standardized format. In areas where it is difficult to find a widely recognized local term, interviewers must be trained to adequately describe the condition. Because night blindness tends to occur in the later part of pregnancy, surveys that measure night blindness among currently pregnant women will usually underestimate the prevalence. Regions with low prevalence of night blindness may necessitate large sample sizes to detect changes at the population level. When analyzing data, cases whose blindness was probably due to visual impairment from other causes are generally excluded. However, DHS reports two indicators: the percentage of all women who report night blindness in the last pregnancy and an adjusted percentage who report night blindness excluding those who report vision problems during the day. The rationale for reporting the unadjusted percentage is to avoid the assumption that (a) women with daytime vision problems (probably mostly myopia) would not be night blind; (b) recall of daytime vision is 100 percent accurate; and (c) positive history of night blindness among women with daytime vision problems is 100 percent inaccurate (WHO, 2009).
While night blindness in women during pregnancy is used as a proxy for VAD and VAD is the main cause of night blindness, Graham et al., (2007) found that iron and riboflavin deficiencies can also increase the risk of night blindness. Zinc deficiency has also been implicated in night blindness (Christian et al., 2001). Research is needed in understanding the effects and interactions of multiple micronutrient deficiencies on night blindness, in addition to testing strategies for simultaneous delivery for prevention and treatment of night blindness during pregnancy.
nutrition, newborn (NB), safe motherhood (SM)
Christian P, Recommendations for Indicators: Night Blindness during Pregnancy—A Simple Tool to Assess Vitamin A Deficiency in a Population, Proceedings of the XX International Vitamin A Consultative Group (IVACG) Meeting, Journal of Nutrition (Supplement) 2002; 0022-3166/02.
Christian P, Khatry SK, Yamini S, et al. Zinc supplementation might potentiate the effect of vitamin A in restoring night vision in pregnant Nepalese women. American Journal Clinical Nutrition 2001;73:1045–51.
Gorstein J, Sullivan KM, Parvanta I, Begin F. Indicators and Methods for Cross-Sectional Surveys of Vitamin and Mineral Status of Populations. The Micronutrient Initiative (Ottawa) and the Centers for Disease Control and Prevention (Atlanta), May 2007. http://www.who.int/vmnis/toolkit/mcn-micronutrient-surveys.pdf
Graham JM, Haskell MJ, Pandey P, Shrestha RK, Brown KH, Allen LH, Supplementation with iron and riboflavin enhances dark adaptation response to vitamin A-fortified rice in iron-deficient , pregnant, nightblind Nepali women, American Journal of Clinical Nutrition 2007; 85:1375-84.
IVACG, 2004,Vitamin A and the common agenda for micronutrients, Report of the XXII IVACG Meeting, Lima, Peru: Nov. 15-17.
IVACG, 2002, Maternal night blindness: A new indicator of vitamin A deficiency, IVACG Statement, Washington, DC: IVACG.
West, KP, Jr. Extent of Vitamin A Deficiency among Preschool Children and Women of Reproductive Age, Journal of Nutrition. September 2002 132: 9
West KP Jr, Katz J, Khatry SK, et al. Low dose vitamin A or ß-carotene supplementation reduces pregnancy-related mortality: a double-masked, cluster randomized prevention trial in Nepal. British Medical Journal 1999;318:570–575.
WHO, 2009, Global prevalence of vitamin A deficiency in populations at risk 1995-2005: WHO database on vitamin A deficiency, Geneva: WHO.