Vitamin D status of newborns in New Zealand

Abstract

Recognition of the important non-skeletal health effects of vitamin D has focused attention on the vitamin D status of individuals across the lifespan. To examine the vitamin D status of newborns, we measured serum levels of 25-hydroxyvitamin D (25(OH)D) in the cord blood of 929 apparently healthy newborns in a population-based study in New Zealand, a country at 41 °S latitude, with strong anti-skin cancer (sun avoidance) campaigns and without vitamin D food fortification. Randomly selected midwives in two regions recruited children. The median cord blood level of 25(OH)D was 44 nmol/l (interquartile range, 29-78 nmol/l). Overall, 19 % of newborns had 25(OH)D levels < 25 nmol/l and 57 % had levels < 50 nmol/l; only 27 % had levels of 75 nmol/l or higher, which are levels associated with optimal health in older children and adults. A multivariable ordinal logistic regression model showed that the strongest determinants of low vitamin D status were winter month of birth and non-European ethnicity. Other determinants of low cord blood 25(OH)D included longer gestational age, younger maternal age and a parental history of asthma. In summary, low levels of vitamin D are common among apparently healthy New Zealand newborns, and are independently associated with several easily identified factors. Although the optimal timing and dosage of vitamin D supplementation require further study, our findings may assist future efforts to correct low levels of 25(OH)D among New Zealand mothers and their newborn children.

Full text

Vitamin D status of newborns in New Zealand
Carlos A. Camargo, Jr
1,2
*, Tristram Ingham
3
, Kristin Wickens
3
, Ravi I. Thadhani
2
, Karen M. Silvers
4
,
Michael J. Epton
4
, G. Ian Town
5
, Janice A. Espinola
1
, Julian Crane
3
and the New Zealand Asthma
and Allergy Cohort Study Group
1
Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, 326 Cambridge Street, Suite 410,
Boston, MA 02114, USA
2
Center for D-receptor Activation Research, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
3
Wellington Asthma Research Group, Department of Medicine, Wellington School of Medicine and Health Sciences, University of
Otago, Wellington, New Zealand
4
Canterbury Respiratory Research Group, Department of Medicine, Christchurch School of Medicine, University of Otago,
Christchurch, New Zealand
5
University of Canterbury, Christchurch, New Zealand
(Received 2 December 2009 – Revised 25 March 2010 – Accepted 1 April 2010 – First published online 29 April 2010)
Recognition of the important non-skeletal health effects of vitamin D has focused attention on the vitamin D status of individuals across the
lifespan. To examine the vitamin D status of newborns, we measured serum levels of 25-hydroxyvitamin D (25(OH)D) in the cord blood of
929 apparently healthy newborns in a population-based study in New Zealand, a country at 418S latitude, with strong anti-skin cancer (sun avoid-
ance) campaigns and without vitamin D food fortification. Randomly selected midwives in two regions recruited children. The median cord blood
level of 25(OH)D was 44 nmol/l (interquartile range, 29 – 78 nmol/l). Overall, 19 % of newborns had 25(OH)D levels ,25 nmol/l and 57 % had
levels ,50 nmol/l; only 27 % had levels of 75 nmol/l or higher, which are levels associated with optimal health in older children and adults.
A multivariable ordinal logistic regression model showed that the strongest determinants of low vitamin D status were winter month of birth
and non-European ethnicity. Other determinants of low cord blood 25(OH)D included longer gestational age, younger maternal age and a parental
history of asthma. In summary, low levels of vitamin D are common among apparently healthy New Zealand newborns, and are independently
associated with several easily identified factors. Although the optimal timing and dosage of vitamin D supplementation require further study,
our findings may assist future efforts to correct low levels of 25(OH)D among New Zealand mothers and their newborn children.
Vitamin D: 25-Hydroxyvitamin D: Newborns: Pregnancy: New Zealand
Nutritional interventions in pregnancy and early childhood
have had a major impact on a variety of maternal and child
health problems
(1)
. The potential benefits of vitamin D
supplementation in pregnancy and early childhood are less
clear
(2)
. Although vitamin D status has important implications
for the long-term bone health of the pregnant mother, it
actually may have more important implications for the general
health of the developing fetus and newborn child. Over the
past decade, numerous studies have reported on the myriad
health effects of vitamin D in adults and, increasingly, in
children
(3)
. The most promising findings in early childhood
are vitamin D-associated increases in growth
(4)
, as well as
inverse associations with type 1 diabetes
(5)
and early child-
hood wheezing
(6,7)
. Nevertheless, the population prevalence
of vitamin D deficiency among newborns – and therefore its
public health importance – remains unclear.
Based largely on the historical efforts to prevent rickets,
the US Institute of Medicine recommends a dietary reference
intake for pregnant women (5 mg/d) that is the same as that
recommended for all individuals from birth to the age of
50 years
(8)
. Because of the possible health risk of low
vitamin D status and emerging evidence that populations
at higher latitudes are at increased risk of vitamin D
deficiency
(3)
, some groups have begun to advocate for
higher doses of vitamin D supplementation during pregnancy
and early childhood. For example, the Canadian Paediatric
Society recently increased their recommendation to up to
50 mg/d for pregnant women and at least 10 mg/d for infants
(9)
.
The characteristics of newborns at increased risk of vitamin D
deficiency are uncertain, but they are assumed to mirror
the risk factors in other age groups (e.g. winter months at
high latitude and increased skin pigmentation).
*Corresponding author: Dr Carlos A. Camargo, fax þ1 617 724 4050, email ccamargo@partners.org
Abbreviation: 25(OH)D, 25-hydroxyvitamin D.
British Journal of Nutrition (2010), 104, 1051–1057 doi:10.1017/S0007114510001674
qThe Authors 2010
British Journal of Nutrition

New Zealand provides an interesting location to examine
‘latent’ vitamin D deficiency, given its high average latitude
(418S), strong anti-skin cancer (sun avoidance) campaigns
and absence of vitamin D food fortification. The sun avoid-
ance campaign is motivated by one of the highest cutaneous
malignant melanoma rates in the world
(10)
, along with con-
cerns about periods of ozone depletion and resulting increases
in UV radiation exposure
(11)
. In this context, the New Zealand
Ministry of Health defines an adequate intake for pregnant
women as 5 mg/d, which is the same as that for adults in
general
(12)
. Although data are limited, the vast majority of
New Zealand women do not take vitamin D supplements
during pregnancy. Indeed, a recent survey suggests that only
28 –33 % of pregnant women in New Zealand take any type
of dietary supplement (e.g. folate) during months 4 –7 of
their pregnancy
(13)
. Paediatric data are also limited, but an
Auckland study of children aged 6 –23 months
(14)
and a
national survey of New Zealand children aged 5 –14 years
found that a substantial number of New Zealand children
are vitamin D deficient. To date, the vitamin D status of
New Zealand newborns has not been reported.
To address this gap in the literature, we measured serum
levels of 25-hydroxyvitamin D (25(OH)D) in the cord
blood of 929 apparently healthy New Zealand newborns to
determine their vitamin D status. Having documented a high
prevalence of vitamin D deficiency (defined as either ,25
or ,50 nmol/l), we then examined factors that independently
predicted vitamin D status at birth.
Experimental methods
Study design and subjects
The New Zealand Asthma and Allergy Cohort Study is a
prospective birth cohort comprising 1105 infants recruited in
Wellington (418S) and Christchurch (438S) between 1997
and 2001. Briefly, expectant mothers were recruited by a
random sample of midwives, health professionals who provide
almost all maternity care in New Zealand. At birth, midwives
or study nurses collected the newborn’s anthropometric details
and cord blood, when available. Study nurses conducted
face-to-face, structured interviews shortly after birth and at
3 months. Full details of recruitment and follow-up have been
presented elsewhere
(15)
. The present study was conducted
according to the guidelines laid down in the Declaration of
Helsinki, and all procedures involving human subjects were
approved by the Wellington and Canterbury Regional Ethics
Committees. Written informed consent was obtained from
each mother.
Cord blood 25-hydoxyvitamin D. The primary outcome
for the present study is the cord blood level of 25(OH)D.
Cord blood was available for 929 participants (84 % of the
original cohort), and this sample is representative of the over-
all study population (data not shown). The cord blood samples
were promptly refrigerated at 248C and then transferred,
within 24 h, to 2808C freezers for long-term storage. Levels
of 25(OH)D were measured using the LIAISON automated
chemiluminescence immunoassay (DiaSorin Stillwater, MN,
USA). The assay has an intra-assay CV of 9 % and an inter-
assay CV of 11 %. The 929 specimens were run in one
batch, sorted by study identification number.
Risk factors. Exposures of interest included study site
(Wellington and Christchurch), gestational age, sex, child’s
ethnicity (European, Ma¯ori, Pacific and Other), birth weight,
month of birth, season of birth, maternal age at birth and par-
ental history of asthma (neither and either). Child’s ethnicity
was assessed with the following question: ‘Which ethnic
group or groups does (child’s name) belong to?’ For analytical
purposes, a child’s ethnicity was assigned using the following
prioritisation: New Zealand Ma¯ori .non-Ma¯ori Pacific
Islander .Other .European. Socio-economic status was
assessed using the New Zealand Deprivation Index 2001
based on the child’s home address at 3 months
(16)
; the index
ranges from 1 (affluent) to 10 (poor).
Data analysis
We performed all the analyses using STATA 10.0 (Stata
Corporation, College Station, TX, USA). The sample was
described using proportions, and means and standard devi-
ations (or medians with interquartile range, where appro-
priate). For outcome analyses, we generated an ordinal
variable from serum 25(OH)D concentrations to describe
vitamin D status in four groups: ,25, 25 –49, 50 –74 and
75 þnmol/l. Unadjusted associations between various new-
born and parental characteristics and vitamin D status were
examined. For each characteristic, we reported the median
25(OH)D concentration, interquartile range and the proportion
of newborns by vitamin D status. To test for the trend in
vitamin D status for each characteristic, we used the
STATA command nptrend, a non-parametric test for trend
based on the Wilcoxon–Mann –Whitney test. To adjust for
potentially confounding effects of covariates, we created a
multivariable ordinal logistic regression model using the
four-level vitamin D status variable as the dependent variable.
Re-analyses of the data – using data-derived quartiles or a
multivariable logistic regression to examine predictors of
vitamin D deficiency per se (serum 25(OH)D either ,25 or
,50 nmol/l) – yielded similar results (data not shown).
A two-tailed P,0·05 was considered statistically significant.
Results
Among the 929 mother–child pairs, midwives recruited 474
pairs (51 %) in the Wellington area and 455 pairs (49 %) in
the Christchurch area. All mothers received free prenatal
care from government-supported midwives. Use of prenatal
vitamins was not consistently recorded by the study personnel,
but was, with the possible exception of folate, uncommon. In
the small subset of women taking a daily multivitamin in
1997–2001, most preparations would have contained a maxi-
mum of 5 mg of vitamin D.
Although 929 mothers consented to participate in the study
and provided cord blood for analyses, 7 mothers did not pro-
vide baseline data (e.g. demographic factors) at the postnatal
visit, leaving 922 newborns in most analyses. Moreover,
additional baseline data (e.g. home address and parental history
of asthma) were collected at 3 months, at which point, another
forty women dropped out of the study. Therefore, the analytical
sample size for multivariable models included a maximum of
882 newborns (i.e. 80 % of the original cohort and 95 % of
the cohort with cord blood 25(OH)D levels).
C. A. Camargo et al.1052
British Journal of Nutrition

Table 1. Characteristics of New Zealand newborns by cord blood 25-hydroxyvitamin D concentration
(Medians, interquartile ranges (IQR) and percentages, n929)
Serum 25-hydoxyvitamin D (nmol/l)
,25 (n180) 25– 49 (n350) 50 – 74 (n146) 75 þ(n253)
nMedian IQR Newborns (%; by row) Pfor trend
Study site
Wellington 474 45 31, 79 18 37 17 28
Christchurch 455 42 27, 77 21 38 14 26 0·12
Gestational age (weeks)
,37 27 64 35, 90 0 33 26 41
37–39 335 47 30, 83 17 36 18 29
40þ555 41 28, 76 22 39 14 25 0·01
Missing 12 51 38, 85
Sex
Male 467 44 30, 80 18 37 18 27
Female 455 44 27, 78 21 38 14 27 0·22
Missing 7 53 39, 99
Ethnicity
European 655 47 31, 83 16 36 16 31
Ma
¯ori 130 41 27, 64 21 45 13 22
Pacific 54 32 19, 47 39 39 9 13
Other 43 31 21, 63 33 33 19 16 ,0·001
Missing 47 42 25, 63
Birth weight (kg)
,3 76 44 30, 77 21 33 18 28
3– 3·9 543 46 30, 80 18 36 17 28
4þ154 41 26, 80 21 40 10 29 0·50
Missing 156 41 29, 71
Month of birth
January 46 84 45, 123 2 28 11 59
February 60 98 82, 121 5 10 7 78
March 58 81 52, 124 3 16 24 57
April 63 63 38, 95 8 29 21 43
May 72 50 36, 81 14 36 19 31
June 75 35 23, 48 27 51 15 8
July 94 33 20, 48 38 40 10 12
August 110 30 22, 41 36 49 10 5
September 111 35 22, 51 30 45 14 11
October 99 40 26, 57 20 51 14 15
November 74 52 35, 77 8 39 26 27
December 60 68 42, 90 7 27 23 43 ,0·001
Missing 7 53 39, 99
Season of birth
Spring (September–November) 284 39 26, 60 21 45 17 17
Summer (December–February) 166 85 49, 111 5 21 14 60
Autumn (March–May) 193 65 41, 100 9 27 21 42
Winter (June–August) 279 32 22, 45 34 47 11 8 ,0·001
Missing 7 53 39, 99
NZ Deprivation Index
1 156 53 32, 94 15 30 19 36
2 86 52 33, 88 16 31 21 31
3 108 41 29, 69 20 42 18 20
4 114 43 31, 78 17 43 15 25
5 76 44 31, 90 11 49 9 32
6 78 44 25, 78 26 32 10 32
7 63 40 29, 68 17 46 16 21
8 63 42 25, 82 25 33 14 27
9 77 48 27, 79 22 31 19 27
10 61 36 23, 48 30 46 10 15 0·001
Missing 47 42 25, 63
Maternal age at birth (years)
,30 409 40 26, 70 23 41 14 22
30–34 358 49 31, 87 17 34 17 32
35–39 121 43 31, 76 18 39 17 26
40þ24 58 36, 83 4 42 21 33 0·15
Missing 17 53 39, 93
Parental history of asthma
Neither 650 46 30, 81 18 37 15 30
Either 172 41 26, 69 23 41 17 19 0·03
Missing 107 41 27, 71
NZ, New Zealand.
Vitamin D status of New Zealand newborns 1053
British Journal of Nutrition

As noted in Methods section, the sample was population
based without any specific exclusion criteria. As expected,
most newborns were term, with a median gestational age of
40 (interquartile range, 39– 41) weeks and a mean birth
weight of 3·6 (SD 0·5) kg. Mean maternal age at birth was
30 (SD 5) years. A slightly higher proportion of children
were born during the spring (September–November, 31 %)
and winter (June –August, 30 %) months. The majority of
newborns were of European ethnicity (71 %), but the major
minority groups of New Zealand also were represented, with
14 % being Ma¯ori and 6 % of Pacific ethnicity. Newborns of
‘Other’ ethnicity (5 %) were predominantly Asian (34 of 43,
or 79 %). Thus, the racial/ethnic mix of the cohort closely
matches that of the overall New Zealand population
(15)
.
Participants had a median cord blood 25(OH)D concen-
tration of 44 nmol/l (interquartile range, 29 –78 nmol/l). Over-
all, 19 % of New Zealand newborns had serum 25(OH)D
levels ,25 nmol/l and 57 % had levels ,50 nmol/l; only
27 % had the 25(OH)D levels of 75 nmol/l or higher. Table 1
shows the associations between various newborn and parental
characteristics and vitamin D status. Looking across the four
categories of 25(OH)D, the median 25(OH)D values were
19, 36, 60 and 100 nmol/l, respectively. The unadjusted
associations between the various characteristics and vitamin
D status were strongest for newborn ethnicity and month
(season) of birth (all Pfor trend #0·001). As expected,
median serum 25(OH)D concentrations peaked in infants
born during summer months, and were lowest for infants
born in the winter. Unadjusted analyses also indicated that
gestational age, New Zealand Deprivation Index and parental
history of asthma were potential determinants of newborn
vitamin D status (all Pfor trend ,0·05).
The newborns of Pacific ethnicity and ‘Other’ (i.e. non-
European, non-Ma¯ori and non-Pacific) ethnicity had the
lowest median 25(OH)D serum concentrations, with values
of 32 and 31 nmol/l, respectively. Indeed, a clear majority of
newborns of Pacific ethnicity (78 %) and Other ethnicity
(66 %) had cord blood 25(OH)D levels ,50 nmol/l. Two-
thirds of Ma¯ori newborns also had 25(OH)D levels
,50 nmol/l, though Ma¯ori children were less likely than the
other non-European groups to have levels ,25 nmol/l.
Adjusting for multiple newborn and parental characteristics
(including socio-economic status), month of birth and
ethnicity remained the strongest determinants of vitamin D
status (Table 2). Newborns born in October through May
were more likely to have a higher vitamin D status than
those born in August (all P#0·001). Those born in February,
the final summer month, were sixty-seven times more likely to
have a higher vitamin D status than those born in August.
Compared with newborns of European ethnicity, newborns
of Pacific ethnicity were 77 % less likely to have a higher
vitamin D status, while those of Other ethnicity were 75 % less
likely to have a higher vitamin D status (both P,0·001).
Those of Ma¯ori ethnicity also seemed less likely to have a
higher vitamin D status, but the estimate was not statistically
significant (P¼0·06).
New Zealand newborns with a gestational age of 40 or more
weeks were less likely to have a higher vitamin D status
than those born between 37 and 39 weeks. Newborns with
older mothers, particularly those over 40 years of age, were
more likely to have a higher vitamin D status than newborns
with younger mothers (age ,30 years). Also, those born to
a parent with a history of asthma were less likely to have a
higher vitamin D status. Parental histories of allergic rhinitis
or eczema were NS predictors of newborn 25(OH)D levels
(data not shown). Other factors that were NS predictors of
vitamin D status, after adjusting for covariates, were study
site, sex, birth weight and New Zealand Deprivation Index.
Discussion
In a population-based cohort of 929 apparently healthy
New Zealand children, we found that cord blood levels of
25(OH)D were generally quite low. Almost one in five
children started life with 25(OH)D levels ,25 nmol/l. Cord
blood 25(OH)D had strong associations with a summer
birth, which was the single strongest predictor of high vitamin
D status. Significant predictors of low cord blood 25(OH)D
were non-European ethnicity, longer gestational age, younger
maternal age and parental history of asthma.
The seasonality of serum 25(OH)D levels in older children
and adults is well documented
(14,17 – 19)
. By contrast, few studies
Table 2. Multivariable ordinal logistic regression model of higher cord
blood 25-hydroxyvitamin D concentrations
(Odds ratios and 95 % confidence intervals, n744 with complete data)
Characteristics OR 95 % CI P
Study site
Wellington Reference –
Christchurch 0·84 0·62, 1·14 0·27
Gestational age (weeks)
,37 1·74 0·60, 5·07 0·31
37–39 Reference –
40þ0·68 0·50, 0·92 0·01
Sex
Male Reference –
Female 0·78 0·59, 1·04 0·09
Ethnicity
European Reference –
Ma
¯ori 0·66 0·43, 1·01 0·06
Pacific 0·23 0·12, 0·45 ,0·001
Other 0·25 0·12, 0·50 ,0·001
Birth weight (kg) 0·80 0·58, 1·09 0·16
Month of birth
January 22·27 10·23, 48·47 ,0·001
February 67·11 28·68, 156·99 ,0·001
March 26·19 12·04, 56·95 ,0·001
April 17·39 8·44, 35·83 ,0·001
May 5·98 3·16, 11·32 ,0·001
June 1·96 1·06, 3·63 0·03
July 1·49 0·82, 2·73 0·19
August Reference –
September 1·59 0·89, 2·84 0·12
October 2·67 1·49, 4·80 0·001
November 6·60 3·57, 12·18 ,0·001
December 12·48 6·31, 24·67 ,0·001
NZ Deprivation Index 0·97 0·92, 1·03 0·30
Maternal age at birth (years)
,30 Reference –
30–34 1·62 1·18, 2·22 0·003
35–39 1·18 0·73, 1·88 0·50
40 þ2·68 1·06, 6·77 0·04
Parental history of asthma
Neither Reference –
Either 0·70 0·53, 0·94 0·02
NZ, New Zealand.
C. A. Camargo et al.1054
British Journal of Nutrition

have examined this issue in the newborn children. In recent
years, vitamin D deficiency in newborns has been reported
in several developing nations, such as India
(20)
and Iran
(21)
.
Of greater relevance to our New Zealand cohort, investigators
in Sydney, Australia (338S), recently reported that vitamin D
deficiency (defined as ,25 nmol/l) was found in 15 % of
pregnant women and 11 % of newborns
(22)
. At more compa-
rable latitudes in the USA, investigators in Pittsburgh (408N)
reported vitamin D deficiency (defined as 25(OH)D ,37·5
nmol/l) in 10 % of white newborns and 47 % of black
newborns in a sample of 400 mother – child pairs
(23)
. Similar
results were reported from Boston (428N), where 80 % of
newborns had 25(OH)D ,50 nmol/l despite seemingly
ample intake of vitamin D by their mothers (e.g. 70 % took
daily prenatal vitamin of 10 mg, 90 % of the sample ate
fish and 93 % drank approximately 2·3 glasses of vitamin
D-fortified milk daily)
(24)
. A study of 123 healthy mother –
child pairs in Athens, Greece (388N), found that vitamin D
deficiency (defined as ,25 nmol/l) was present in 20 % of
pregnant women and 8 % of newborns
(25)
. We are not aware
of prior studies that have examined how seasonal patterns
of cord blood 25(OH)D might differ between the ethnic
populations of New Zealand. The low 25(OH)D levels of
Pacific newborns raise significant concerns for this important
and growing segment of the New Zealand population.
At a minimum, our data suggest that New Zealand women
should consider vitamin D supplements during the late autumn
and winter to offset their likely decline in vitamin D during
these months with less UVB exposure. The optimal timing
and dosage of maternal vitamin D remain unknown, with
most groups recommending 5 mg/d
(8)
but others recommend-
ing up to 50 mg/d
(9)
. A recently completed trial of pregnant
women in South Carolina provided even higher doses
(100 mg/d) throughout pregnancy, and this regimen did not
appear to have caused any measurable harm (B. Hollis,
personal communication). Nevertheless, others have appro-
priately cautioned against the use of seemingly high doses
of vitamin D without better safety data
(26)
. Clearly, there is
an urgent need for further research in this novel area of
human nutrition.
The lower vitamin D levels of dark-skinned individuals also
are consistent with prior reports among older children and
adults
(3)
. Skin pigment interferes with vitamin D synthesis in
the skin, and it has been estimated that dark-skinned indi-
viduals require to spend five to ten times as long in the
sunlight to create the same amount of vitamin D as their
light-skinned counterparts
(27)
. To date, there are very sparse
data on the vitamin D status of the Ma¯ori and Pacific children
of New Zealand. The only other published work on this topic,
among New Zealand children aged 6 – 23 months
(14)
and aged
5– 14 years
(18)
, also found that the highest prevalence of
vitamin D deficiency was among Pacific, rather than among
Ma¯ori, children. Our study extends this finding to newborns,
and demonstrates that this difference is independent of several
pregnancy-related and socio-economic factors. Although skin
pigmentation is the most likely explanation for the observed
ethnic differences, the contribution of other genetic or
environmental differences merits further study.
The other independent correlates of low vitamin D status
included longer gestational age, younger maternal age and
parental history of asthma. We lack data on gestational
diabetes, but note that this condition is associated with
longer gestational age and may be more common in mothers
with vitamin D deficiency
(28)
. Moreover, a longer gestational
age might provide further opportunity for the developing
fetus to draw upon a mother’s depleted reserves – a scenario
that argues against a single dietary reference intake for
pregnant and non-pregnant women alike
(8)
. It is more difficult
to explain the maternal age finding. Were younger mothers
more likely to comply with sun avoidance or less likely to
take prenatal vitamins? We believe that this finding requires
replication and further study. The same is true of the associ-
ation between parental history of asthma and lower cord
blood levels of 25(OH)D. Confirmatory results would be of
likely relevance to recent reports of an inverse association
between vitamin D status and several asthma-related out-
comes
(6,7,29)
.
What is the health impact of low cord blood levels of
25(OH)D? To date, the paucity of outcome data prevents
any definitive statements, but there is a growing international
interest in this issue. In recent years, the European and North
American investigators have found higher risk of several
important childhood diseases among those with low vitamin
D status, including type 1 diabetes
(5)
, wheezing
(6,7)
and
winter-related eczema
(30)
. As research advances on the role
of vitamin D in pregnancy and early childhood, evidence
about health outcomes will surely grow. These future studies
will provide data to better inform healthcare providers and
public health officials about what exactly constitutes vitamin
D ‘deficiency’ in newborns, as well as the levels that are
associated with optimal health.
Another research need suggested by our work is the
development of an equation to link the more easily tested
maternal level of 25(OH)D with the expected level of a
child at birth. Unfortunately, we did not measure concurrent
maternal 25(OH)D levels, and are unable to examine this
issue. Vitamin D metabolites, especially 25(OH)D, are
known to cross the placenta
(31)
. Prior studies, based on rela-
tively small samples, suggest that maternal levels of 25(OH)D
are approximately 10 –15 nmol/l higher than the levels in
cord blood
(20,23)
. By contrast, a study from Greece found
significantly lower average levels of 25(OH)D in 123 term
mothers (41 nmol/l) than in the cord blood (51 nmol/l)
(25)
.
Population-based studies of diverse samples are needed.
The development of such an equation would facilitate the
development of studies on the potential impact of introducing
a maternal supplement during pregnancy or early childhood –
without the logistical complexity and research challenges of
measuring 25(OH)D levels in cord blood.
The present study has other potential limitations. Although
the study lacks data on food intake during pregnancy, non-
fortified food sources of vitamin D have limited effect on serum
25(OH)D levels
(3,24)
. The study also lacks data on maternal
25(OH)D levels from earlier in the pregnancy; it would have
been interesting to examine the relationship of earlier levels
with cord blood levels. Although estimates vary, the half-life
of serum 25(OH)D in adults is 2 – 3 weeks
(8)
. If this was
true in cord blood, it would suggest that the measured levels
reflect maternal– fetal status during the final months of
pregnancy. Sun-related behaviours and dietary intake may
change over the course of a pregnancy, but these changes
are relatively minor
(32)
and probably, they are not influenced
Vitamin D status of New Zealand newborns 1055
British Journal of Nutrition

by baseline levels of maternal 25(OH)D. Thus, we believe that
the cord blood values provide a reasonably accurate way to
rank-order mothers by their vitamin D status during
pregnancy – and, therefore, to identify characteristics of
mothers who might benefit from higher dose vitamin D
supplementation.
In summary, vitamin D deficiency and insufficiency are
common in apparently normal newborns in New Zealand.
The health implications of this finding are not clear, but a
growing body of evidence suggest that lower levels of vitamin
D are associated with important health problems of childhood.
Given the absence of any compelling evidence for an adverse
effect of increased vitamin D intake among pregnant women,
and with some professional societies already recommending
much higher doses
(9)
, we believe that such a public health
campaign merits serious consideration. The optimal timing
and dosage of vitamin D supplementation require further
study. In the meantime, however, our findings can help
identify individuals at increased risk, and thereby assist
efforts to correct the low levels of vitamin D among most
New Zealand mothers and their newborn children.
Acknowledgements
We thank the midwives in Wellington, Porirua and Canterbury
for their assistance with recruitment, and all the families
and children for their participation. The New Zealand
Asthma and Allergy Cohort Study Group consisted of
J. C., M. Duignan, M. J. E., D. Fishwick, P. Fitzharris,
T. I., V. Irvine, R. Kelly, P. Lampshire, J. Lane, P. Leadbitter,
C. MacDonald, F. McCartin, S. McLeod, A. Nicholson,
P. Pattemore, K. Roff, G. Sawyer, R. Siebers, G. I. T.,
K. W., H. Wilson and K. Withell. This work was supported
by grants from the Health Research Council of New Zealand,
the David and Cassie Anderson Bequest (Wellington,
New Zealand), and the Massachusetts General Hospital
Center for D-receptor Activation Research (Boston, MA,
USA). None of the authors has any potential conflicts of
interest. The authors’ contributions are as follows: C. A. C.
had full access to all the data in the study, and takes respon-
sibility for the integrity of the data and the accuracy of the
data analysis. C. A. C., G. I. T. and J. C. were involved in
the study concept and design. C. A. C., T. I., K. W., R. I. T.,
M. J. E., G. I. T. and J. C. were involved in the acquisition
of data. C. A. C., T. I., K. W., K. M. S., J. A. E. and J. C.
were involved in the analysis and interpretation of data.
C. A. C. was involved in the preparation of the manuscript.
The critical revision of the manuscript for important intellec-
tual content was done by C. A. C., T. I., K. W., R. I. T.,
K. M. S., M. J. E., G. I. T., J. A. E. and J. C. C.; A. C. and
J. A. E. performed the statistical analysis. C. A. C., M. J. E.
and J. C. were involved in the study supervision.
References
1. Anonymous (2009) Women, Infants, and Children (WIC)
Website. http://www.fns.usda.gov/wic/ (accessed 11 January
2009).
2. Hollis BW & Wagner CL (2004) Assessment of dietary vitamin
D requirements during pregnancy and lactation. Am J Clin Nutr
79, 717–726.
3. Holick MF (2007) Vitamin D deficiency. N Engl J Med 357,
266–281.
4. Javaid MK, Crozier SR, Harvey NC, et al. (2006) Maternal
vitamin D status during pregnancy and childhood bone mass
at age 9 years: a longitudinal study. Lancet 367, 36– 43.
5. Hypponen E, Laara E, Reunanen A, et al. (2001) Intake of
vitamin D and risk of type 1 diabetes: a birth-cohort study.
Lancet 358, 1500–1503.
6. Camargo CA Jr, Rifas-Shiman SL, Litonjua AA, et al. (2007)
Maternal intake of vitamin D during pregnancy and risk of
recurrent wheeze in children at 3 y of age. Am J Clin Nutr
85, 788–795.
7. Devereux G, Litonjua AA, Turner SW, et al. (2007) Maternal
vitamin D intake during pregnancy and early childhood
wheezing. Am J Clin Nutr 85, 853 – 859.
8. Standing Committee on the Scientific Evaluation of Dietary
Reference Intakes (1997) Dietary Reference Intakes for
Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride.
Washington, DC: Institute of Medicine.
9. Canadian Paediatric Society (2007) Vitamin D supplementation:
recommendations for Canadian mothers and infants (Position
Statement FNIM 2007-01). Paediatr Child Health 12, 583 – 589.
10. World Health Organization (2001) GLOBOCAN: Cancer
Incidence, Mortality and Prevalence Worldwide, IARC Cancer-
base No. 5, Version 1.0. Lyon: IARC.
11. Allan W, Riedel K, McKenzie R, et al. (2009) Atmosphere –
ozone and ultraviolet radiation. In Te Ara – Encyclopedia
of New Zealand. http://www.TeAra.govt.nz/en/atmosphere/4
(accessed 11 January 2009).
12. Ministry of Health (2005) Food and Nutrition Guidelines for
Healthy Pregnant and Breastfeeding Women: A Background
Paper: Draft for Consultation. Wellington: Ministry of Health.
13. Watson PE & McDonald B (1999) Nutrition During Pregnancy:
A Report to the Ministry of Health. Auckland: Massey
University (Albany Campus).
14. Grant CC, Wall CR, Crengle S, et al. (2009) Vitamin D
deficiency in early childhood: prevalent in the sunny South
Pacific. Public Health Nutr 12, 1893–1901.
15. Epton MJ, Town GI, Ingham T, et al. (2007) The New Zealand
Asthma and Allergy Cohort Study (NZA
2
CS): assembly,
demographics and investigations. BMC Public Health 7, 26.
16. Salmond C & Crampton P (2001) NZDep2001 Index of
Deprivation, User’s Manual. Wellington: Department of Public
Health, Wellington School of Medicine and Health Sciences.
17. Hanley DA & Davison KS (2005) Vitamin D insufficiency in
North America. J Nutr 135, 332– 337.
18. Rockell JE, Green TJ, Skeaff CM, et al. (2005) Season and
ethnicity are determinants of serum 25-hydroxyvitamin D
concentrations in New Zealand children aged 5 –14 y. J Nutr
135, 2602–2608.
19. Brot C, Vestergaard P, Kolthoff N, et al. (2001) Vitamin D
status and its adequacy in healthy Danish perimenopausal
women: relationships to dietary intake, sun exposure and
serum parathyroid hormone. Br J Nutr 86, Suppl. 1, S97– 103.
20. Sachan A, Gupta R, Das V, et al. (2005) High prevalence
of vitamin D deficiency among pregnant women and their
newborns in northern India. Am J Clin Nutr 81, 1060 – 1064.
21. Maghbooli Z, Hossein-Nezhad A, Shafaei AR, et al. (2007)
Vitamin D status in mothers and their newborns in Iran. BMC
Pregnancy Childbirth 7,1.
22. Bowyer L, Catling-Paull C, Diamond T, et al. (2009) Vitamin
D, PTH and calcium levels in pregnant women and their
neonates. Clin Endocrinol (Oxf) 70, 372–377.
23. Bodnar LM, Simhan HN, Powers RW, et al. (2007) High
prevalence of vitamin D insufficiency in black and white
pregnant women residing in the northern United States and
their neonates. J Nutr 137, 447–452.
C. A. Camargo et al.1056
British Journal of Nutrition

24. Lee JM, Smith JR, Philipp BL, et al. (2007) Vitamin D
deficiency in a healthy group of mothers and newborn infants.
Clin Pediatr (Phila) 46, 42– 44.
25. Nicolaidou P, Hatzistamatiou Z, Papadopoulou A, et al. (2006)
Low vitamin D status in mother– newborn pairs in Greece.
Calcif Tissue Int 78, 337 – 342.
26. Wjst M (2006) The vitamin D slant on allergy. Pediatr Allergy
Immunol 17, 477– 483.
27. Chen TC, Chimeh F, Lu Z, et al. (2007) Factors that influence
the cutaneous synthesis and dietary sources of vitamin D. Arch
Biochem Biophys 460, 213 – 217.
28. Maghbooli Z, Hossein-Nezhad A, Karimi F, et al. (2008)
Correlation between vitamin D
3
deficiency and insulin resist-
ance in pregnancy. Diabetes Metab Res Rev 24, 27 – 32.
29. Erkkola M, Kaila M, Nwaru BI, et al. (2009) Maternal vitamin D
intake during pregnancy is inversely associated with asthma and
allergic rhinitis in 5-year-old children. Clin Exp Allergy 39,
875–882.
30. Sidbury R, Sullivan AF, Thadhani RI, et al. (2008) Rando-
mized trial of vitamin D supplementation for winter-related
atopic dermatitis in Boston: a pilot study. Br J Dermatol 159,
245–247.
31. Hillman LS & Haddad JG (1974) Human perinatal vitamin D
metabolism. I. 25-Hydroxyvitamin D in maternal and cord
blood. J Pediatr 84, 742– 749.
32. Rifas-Shiman SL, Rich-Edwards JW, Willett WC, et al. (2006)
Changes in dietary intake from the first to the second trimester
of pregnancy. Paediatr Perinat Epidemiol 20, 35 – 42.
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