Predictors of periconceptional folic acid supplement use among New Zealand women and the potential of mandatory fortification to improve inequalities in folic acid intakes

Abstract

Neural tube defects (NTD) are among the most serious congenital malformations, and are unique in that the majority of cases are preventable by the intake of folic acid before and during pregnancy. Globally, few women comply with periconceptional folic acid supplement recommendations, and poor compliance has repeatedly been associated with lower socioeconomic position, minority ethnicity status and unintentional pregnancy. To address inadequate supplement use, many countries have permitted or mandated the addition of folic acid to specified foods. In September 2009, the folic acid fortification of bread (135 μg/100 g bread) was to become mandatory in New Zealand. However, due to political and manufacturer objection, the mandate was deferred until May 2012, with no guarantee of implementation. The primary aim of this research was to describe periconceptional folic acid supplement use and bread intake among New Zealand women for the purpose of informing public health policy prior to the potential introduction of the fortification mandate.

This was achieved by addressing three specific objectives: 1) To describe the characteristics of women who fail to achieve adequate periconceptional folic acid intakes from supplements and to investigate the effect of mandating the folic acid fortification of bread at proposed levels on these associations; 2) To describe folate knowledge and consumer behaviour among pregnant women; and 3) To estimate periconceptional folic acid intakes that would be derived from bread if fortification was mandated as proposed. A survey of postpartum women was conducted using a self-administered questionnaire. Details on supplement use and bread intake before and during pregnancy, folate knowledge and maternal socio-demographic characteristics were obtained. The consumption of three or more slices of bread per day (118–150 μg folic acid/d) was the criterion for adequate folic acid intake under mandatory fortification. Of the 968 women invited to participate, 758 (78%) agreed. Thirty-three percent (33%) of women reported having used folic acid supplements as recommended. Increasing knowledge of folic acid recommendations was associated with higher supplement uptake among women who planned their pregnancies (P=0.001 for linear trend). Socio-demographic predictors of poor folic acid intake from supplements, including younger age, increasing parity, minority ethnicity status, lower education and less income, were rendered either non-significant or appreciably attenuated when mandatory fortification was modelled. Notably, the fully adjusted odds ratio for pregnancy planning was reduced from 17.24 (95% confidence interval (CI): 8.13–36.55) to 2.61 (95% CI: 1.73–3.93; both P<0.001). Median bread intake before conception (2 slices/d) was below that of previous data upon which the current fortification proposal was based (3–4 slices/d). Sub-groups predicted to derive less than adequate folic acid intakes from the proposed policy were Asian women and those with a postgraduate qualification. Few women comply with periconceptional folic acid recommendations and thus the maximal prevention of NTD is still far from being attained. Data from this survey demonstrate that mandatory fortification benefits segments of the population less likely to use supplements. This finding has compelling policy implications in countries yet to mandate the folic acid fortification of a staple food.