Inequities in pre-pregnancy folic acid use in Central and South Auckland: secondary analysis from a postpartum contraception survey

Introduction

Neural tube defects (NTDs) occur when the neural tube does not fully close early in foetal development, resulting in incomplete formation of the spine, membranes (spina bifida), or cerebrum and cerebellum (anencephaly). They are among the most common severe birth defects. The rate of NTDs in Aotearoa New Zealand (NZ) is 10.3 per 10 000 pregnancies.¹

Rates of NTD by ethnicity are only available as a proportion of live births. Rates are significantly higher for Maaori (4.58 per 10 000 live births) compared to European/other women (2.81 per 10 000 live births), and higher, though not statistically significantly, for Pacific peoples (4.09 per 10 000 live births) compared to European/other women.¹

Folate is an essential vitamin. Supplementation with folic acid, the synthetic form of folate, reduces the risk of NTDs, cardiac, and oral cleft defects. The neural tube closes on day 28 after fertilisation and adequate folate levels pre-pregnancy are essential to reduce the risk of malformation.^2–5 Manatuu Hauora recommends the use of 800 microgram folic acid daily, for 4 weeks pre-pregnancy until 12 weeks’ gestation. For pregnancies where additional risk factors are present (eg a personal or family history of NTD, previous child with a NTD, diabetes, use of medications that affect folate metabolism), a 5 mg daily dose is recommended.⁶

A population-based survey showed only 16% of NZ women of child-bearing age had blood folate levels above the World Health Organization (WHO) recommended level for minimal risk of NTDs.¹ In addition, with almost half of pregnancies unplanned,⁷ the NZ government moved to mandate fortification of non-organic wheat flour sold for bread making, from 2023, replacing the existing legislation of voluntary fortification.⁸ Mandatory fortification of wheat is safe, with no absolute increase in risk of prostate, breast, or colorectal cancer, and no evidence suggesting increased rates of twin pregnancy (after controlling for assisted reproductive technology).¹ In other countries, mandatory fortification has been associated with reduced rates of NTD.⁹ Mandatory fortification in New Zealand is predicted to result in 14–20 fewer NTD among live births annually.¹

Despite fortification, it is expected that a large proportion of people will continue to have folate levels below WHO recommendations.¹ Supplementation 1 month pre-pregnancy and for the first trimester is still recommended to reduce the risk of NTD.¹⁰ It is critical that we prioritise this message to groups at greatest risk of having babies with NTD, including those where pre-pregnancy supplementation is already low. However, despite the observed inequities in NTD rates by ethnicity, there are little published data describing folic acid supplementation, or supplementation by ethnicity and other demographic variables in NZ. A 2012 post partum survey found rates of supplementation at 54% for planned pregnancies and less then two-thirds of women were aware that folic acid supplements reduced the risk of birth defects. In this study for women with planned pregnancy, Maaori Pacific and Asian women were less likely to receive information before conception than New Zealand European women.¹¹

The aim of the present study was to describe the proportion of recently postpartum people who reported using folic acid pre-conception, and to determine whether factors such as ethnicity, parity, maternal age, pregnancy intendedness, location of birth and type of pregnancy care provider are associated with folic acid supplementation. We also aimed to explore independent associations between ethnicity, parity, maternal age, location of birth, pregnancy care provider and folic acid supplementation among women whose pregnancies were intended.

Methods

We conducted secondary analysis of cross-sectional survey data collected at Te Whatu Ora Te Toka Tumai (Auckland) and Counties Manukau birthing facilities (two tertiary and four primary birthing units) in 2020, birthing approximately 14 000 women per year combined, as part of an anonymous postnatal contraception survey. Full details of the survey and methodology are published elsewhere.^7,12 In brief, study investigators approached eligible patients between day 1 and 7 postpartum during their inpatient stay, irrespective of mode of delivery, explained the study and invited them to participate. Patients were excluded if they were discharged home within 6 h, required a translator, delivered a baby <23 weeks’ gestation or experienced a perinatal loss. At Counties Manukau, all women were approached in a 2-week period. Te Toka Tumai recruitment was continued for some ethnic groups until a cohort was achieved with adequate numbers for analysis by ethnicity.

Basic demographic data were collected including parity, maternal ethnicity (self-defined using the standard NZ Census question, and prioritised according to NZ protocols¹³), location at given birth, and type of maternity care received (community or self-employed midwifery, private obstetrician and hospital-based midwifery care). Relevant to this study, the survey included questions described in the London Measure of Unplanned Pregnancy (LMUP).¹² This measure includes six questions, one of which asks ‘Before you became pregnant, did you do anything to improve your health in preparation for pregnancy?’. The responses for this question include ‘took folic acid’. There is also an option, ‘took some other action, please describe____’ for which some women described pre-pregnancy (multi)vitamin preparations known to contain folic acid. Response to the specific option, and free text describing these additional preparations, were taken to represent pre-pregnancy folic acid supplementation in this study.

The study was approved by the New Zealand Health and Disability Ethics Committee (HDEC) as an amendment to the original contraception survey application, and locality approval at Te Whatu Ora Te Toka Tumai and Counties Manukau facilities was also obtained.

Results

In total, 140 people were surveyed at Te Whatu Ora Counties Manukau and 258 at Te Whatu OraTe Toka Tumai facilities in 2020. Overall, 398 participants completed the survey. Of those eligible and approached, the response rate was (140/149) 94% at Te Whatu Ora Counties Manukau and (258/315) 82% at Te Whatu Ora Te Toka Tumai.

Maternal ethnicity, parity, age, pregnancy care provider, and pregnancy intendedness of the women in the study differed by unit, but were similar to the characteristics of all women birthing at Te Whatu Ora Te Toka Tumai and Counties localities in 2020 (Table 1).

Overall, 182 of 398 (46%) of those surveyed reported taking folic acid supplementation pre-pregnancy. Rates differed by locality, ethnicity, parity, maternal age, and type of pregnancy care (Table 2). Of participants who intended to be pregnant, 58% reported taking pre-pregnancy folic acid compared to 21% who did not, and 27% who reported ambivalence (slightly agree or slightly disagree to the statement ‘I intended to be pregnant with this baby’) (Table 2).

Twenty-five percent of Maaori participants reported folic acid supplementation (Tables 1, 2) compared to 22% of Pacific, 46% of Indian, 58% of Asian, and 64% of participants of other (including European) ethnicities (Table 2). Those having their first baby were more likely to take supplementation than those having their fourth or later babies (Table 2).

Pregnancy intention varied by locality, ethnicity, maternal age, and type of pregnancy care (Table 3). Locality of birth, parity, maternal age, and type of pregnancy care also varied by ethnicity (Table 4). The multivariable analyses conducted using the data obtained from the 262 participants whose pregnancies were reported as intended are given in Table 5. The associations seen between locality, ethnicity, parity, age, and pregnancy caregiver and folic acid supplementation were attenuated once adjusted for each other. Supplementation was more likely only for the ‘Other’ ethnic grouping (including European, Middle Eastern, Latin American, and African) compared to Maaori (aOR 5.3 (95% CI 1.3, 21.8)), older age (≥30 years compared to <30 years) (aOR 2.1 (1.0, 4.1)), and private obstetrician (aOR 4.2 (1.6, 10.9)) compared to Community (self-employed) midwifery care. After adjusting for other factors, there was no difference in supplementation observed by locality of birth.

Discussion

This study demonstrates suboptimal pre-pregnancy folic acid supplementation in those intending to become pregnant (58% supplementation rate), as well as those not planning their pregnancy (21% supplementation rate). Among those who reported having a planned pregnancy, European and MELAA ethnicities, older maternal age, and private obstetrician care independently predicted folic acid use.

Pregnancy intention was the most significant predictor of folic acid supplementation in this study. We speculate that facilitating reproductive autonomy, including information about and access to contraception, could optimise pre-pregnancy folic acid supplementation.

However, we note that more than one-third of those with a planned pregnancy were not supplementing with folic acid. Additional approaches (to fortification) will be required to optimise folate levels before or at the earliest opportunity in pregnancy. This presumably requires greater public health awareness and education.¹

In a 2010 telephone survey of women of child bearing age commissioned by the New Zealand Food Safety Authority, more than half (57%) of respondents rated their knowledge of folate/folic acid as a ‘0’, ‘1’ or ‘2’ (out of 10), with 23% rating their knowledge as ‘0 – don’t know anything about it at all’.¹⁴ Tools like pre-pregnancy checklists that include folic acid supplementation (and other health promotion behaviours) to use at the time of contraception discussions (and especially when removing LARCs) might help aid clinician-prompted conversations.

The significantly higher folic acid supplementation reported among European participants might contribute to the lower NTD rates observed for European compared to aaori in NZ. This is concerning. The New Zealand Health System has an obligation to Maaori under The Treaty of Waitangi with a responsibility to actively protect wellbeing and work in partnership with Maaori to achieve health equity.¹⁵ Our study shows that these obligations are not being met. European, Middle Eastern, Latin American, and African women had significantly greater access to folate supplementation compared with Maaori, after adjusting for other variables, which is consistent with the findings of previous research.¹⁶ More work needs to be done to dissemble the barriers to equitable supplementation, including the wider determinants of health such as health literacy, access, cultural safety, colonialism, political context and systemic racism.¹⁷ Importantly, ongoing monitoring of policies and interventions must occur to ensure the New Zealand Health System is addressing the current ethnic disparities in folic acid levels, supplementation and consequently rates of NTD. It is expected that mandatory fortification will narrow the inequity in NTD rates in NZ, as it has in the Australian population.⁹

Other findings of this study were that those who had intended pregnancies and were older, and/or under care of a private obstetrician, were two- and four- fold more likely compared to younger people and people under community midwifery care to have reported folic acid supplementation after adjusting for other factors. Age is a recognised predictor of ‘medication adherence’¹⁸ and this study aligns with previous studies reporting maternal age as a factor for increased knowledge about folic acid, its relevance to pregnancy¹⁴ and predicting folic acid supplementation.¹⁹

Care by a private obstetrician likely reflects socioeconomic advantage, a factor we were unable to adjust for in this study.²⁰ Private obstetricians are chosen by a small proportion (3.92%) of New Zealand women, with 89.6% choosing a midwife as their Lead Maternity Carer and 0.14% a general practitioner in 2020.²¹

This study was performed at two large and diverse metro Auckland maternity facilities and achieved a very high response rate. Participants were approximately representative of birthing parents in those sites. Anonymous survey methodology is likely superior to pharmacy data as folic acid is prescribed as well as purchased over the counter as part of a pregnancy multivitamin, and prescription does not measure compliance. This survey could be repeated over time to determine whether there is a change in adjuvant uptake of supplements after the implementation of compulsory wheat flour fortification. Given the high levels of folate recommended to prevent NTDs, it will be important to evaluate the effect of the new policy on serum levels.

There are limitations. Data relied on self-reporting by participants. Also, data on exact periods of use were not collected. Despite being an anonymous survey, respondents might have forgotten or felt inclined to report what they should have done rather than what they did. There was no assessment of whether the appropriate dose was taken based on risk factors. The survey also excluded a low number of people because they required a translator or because they went home directly after birthing. The survey collected information from the two sites during different periods, and at one site the collection was purposive for some ethnicity groups, and these methodologic differences might have led to some bias in the findings.

This survey was undertaken in two localities in the ethnically diverse areas of central and south Auckland. The rates of both private obstetrician care and DHB- led care are higher in these hospital regions (Table 1) than in Aotearoa as a whole, and the results might therefore not be generalisable to the rest of the country.

Although national fortification of wheat is important, we believe that folic acid supplements should be freely available, and that appropriate, targeted education needs to be planned to raise awareness of the need for supplementation pre-pregnancy. Support, including funding for clinicians to undertake opportunistic pre-pregnancy counselling, is also important. We propose a future prospective study of folate blood levels in the early weeks of pregnancy to determine the success of flour fortification. This might be possible in a general practice environment, as women often access a general practictioner for pregnancy testing/confirmation, and LMC care might be delayed until beyond the window of opportunity.²²

Mixed methods research exploring awareness of, attitudes towards, and acceptability of folic acid supplementation within communities would help to understand reasons for, and address, inequity in use.

Conclusion

Auckland has low rates of pre-pregnancy folic acid supplementation, even among those with intended pregnancy. There is significant ethnic disparity in supplementation, which might contribute to the disproportionate neural tube defect rate in Maaori whaanau.¹⁰ Fortification is a promising step forward. However, the strategy might not succeed if concurrent efforts do not continue to support women with reproductive autonomy and disseminate knowledge about the continued importance of supplementation pre-pregnancy to maximally reduce the risk for future tamariki (children).

Data availability

The data that support this study are available in the article.

Conflicts of interest

The authors declare that they have no conflicts of interest.

Declaration of funding

This work was supported by the Strathlachlan Fund (NZD $10 000 grant) and a University of Auckland summer student scholarship. The sponsors had no role in the study design, collection, analysis or interpretation of data, writing of the report or decision to submit for publication.