  |
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Journal of the New Zealand Medical Association,
04-June-2004, Vol 117 No 1195
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Comparison of Maori and non-Maori maternal and fetal iron
parameters
Diane Emery, David Barry
Iron deficiency is a preventable heath problem that affects
a large number of New Zealand infants.1,2
Little progress has been made in the last 42 years since the first paper
(identifying iron deficiency as a problem) was
published.3 Iron deficiency is common amongst
children living in underprivileged circumstances; children of Maori and Pacific
ethnicity are highly represented in this
group.1,2
Iron requirements are high during infancy, and it is during
this time that major deleterious effects of tissue iron deficiency are seen.
These include impaired brain development, altered mood, reduced weight gain,
fatigue, and impaired immunity.4 Neurological
affects (such as altered behaviour and development in infants, and decreased
learning in children) have been shown to occur in the presence of iron
deficiency, even in the absence of anaemia.5,6
Some studies have shown that cognitive function may not improve in
iron-deficient anaemic infants following iron
therapy.7 This suggests that prevention of iron
deficiency in young New Zealanders is extremely important as it may stop them
from achieving their full potential.
To prevent the development of iron deficiency in infancy, it
is necessary to understand whether it occurs during the pre-, peri- or postnatal
period. Peri-natal acquisition of iron stores has been shown to be affected by
time of cord clamping in Indian infants.8
Postnatal iron stores have been reported to be greatly affected by diet,
especially from 6 months of age.9 There are
conflicting reports regarding pre-natal acquisition of iron in the fetus, the
question being whether maternal iron status affects, or is independent of, the
fetal iron status.10–19 This study was
undertaken in the Hawke’s Bay region where iron deficiency, especially in
Maori infants, is a problem. This study investigated the associations between
maternal and fetal iron stores.
MethodsThe study was performed at
Hastings Memorial Hospital in Hawke’s Bay, New Zealand. The study period
was between December 1997 and August 1999. A total of 3145 women delivered
babies during this period, this included all elective and emergency caesarian
sections and vaginal deliveries. 179 women, of whom 38 were Maori, had elective
caesarian sections performed. 146 women were eligible, of whom 85% were
consented and 15% were missed due to the consenting doctor being unavailable.
124 women participated in the study. A sample size of 27 per ethnic group would
have 80% power at the 0.05 level of significance to show that a correlation of
0.5 was different from a correlation of 0.
Women who delivered by elective caesarian section were
included in the study. Women were excluded if they suffered medical conditions,
had complications of pregnancy, or delivered prior to 36 weeks’ gestation.
The decision to only include women delivering by elective caesarian section
allowed a standard interval of time (less than 48 hours) between maternal and
cord blood samples to be taken. This also allowed maternal blood to be taken
when the mother was not in established labour. However, the results from this
study must be interpreted with the consideration that only women delivering by
elective caesarian section were included.
On the day prior to delivery, venous blood samples were
taken from women for measurement of serum haemoglobin, ferritin, and iron. Cord
blood samples were taken at caesarian section for measurement of haemoglobin,
ferritin, and iron. Caesarian section and blood-taking techniques were not
influenced by cultural preferences, these being the same for Maori and
non-Maori. The hospital’s laboratory analysed the blood samples. During
1998, the analysers were upgraded.
Haemoglobin was analysed using a Technicon H1 machine,
which was replaced by a Coulter STKs. Cyanmethaemoglobin reagent was used.
Ferritin was analysed using an Abbott IMX which was replaced by an Abbott Axsym.
Dedicated Abbott reagents were used. Iron was analysed using a Hitachi 911
followed by a Hitachi 917. Roche reagents were used.
SAS version 6.12 was used for statistical analysis.
Separate regression models for each of the parameters (haemoglobin, iron, and
ferritin) were used to investigate whether maternal levels predicted cord blood
levels. Ethnicity was included in the models.
Consent was obtained from all participants involved in
the study. The Hawke’s Bay Ethics Committee approved the study.
ResultsMaori and non-Maori maternal serum
and cord blood haemoglobin, ferritin, and iron were compared using T tests.
Twenty-five percent of the study population was Maori, which was comparable to
the percentage of Maori (22%) in the Hawke’s Bay
Region.20 Maori mothers were found to have a
significantly lower serum haemoglobin level compared to non-Maori (p=0.002).
However, other blood parameters indicating maternal iron levels (ferritin
[p=0.2] and iron [p=0.8]) were not significantly different between the two
groups.
Thus, although Maori mothers had lower haemoglobin values,
they were not more iron-deficient then their non-Maori counterparts in our
study. The cord haemoglobin (p=0.9) and cord iron (p=0.8) levels of Maori and
non-Maori neonates were not significantly different, however cord ferritin
(p=0.01) was significantly lower (Table 1).
Table 1. Comparison of blood parameters for Maori and
non-Maori
*Haemoglobin.
Table 2. Regression results from models with one
maternal blood predictor and ethnicity
A positive slope indicates an increased cord blood
outcome for Maori. A negative slope indicates a decreased cord blood outcome for
Maori.
The relationship between maternal and cord blood was
analysed using separate regression models for each of the parameters
(haemoglobin, iron, and ferritin). Ethnicity was included in the models. The
interactions of ethnicity on maternal blood were not found to be significant
(p>0.5) so Maori and non-Maori data were analysed together. No relationship
was found for any of the parameters investigated. Maternal haemoglobin did not
predict cord haemoglobin (p=0.95), iron (p=0.9), or ferritin (p=0.7); maternal
iron did not predict cord haemoglobin (0.99), iron (p=0.3), or ferritin (p=0.2);
and maternal ferritin did not predict cord haemoglobin (p=0.4), iron (0.8), or
ferritin (p=0.7), respectively (Table 2).
Prior to the analysis, the sample size was reduced by loss
of blood samples secondary to blood clotting, and insufficient specimens taken
(Table 1).
DiscussionThe mothers in our study had normal
iron status or were mildly-to-moderately anaemic. Analysis of the study group
showed no statistical relationship between maternal venous and fetal cord blood
haemoglobin, iron, and ferritin levels. This result suggested that iron stores
in the fetus were not adversely affected by mild-to-moderate anaemia in the
mother—thus supporting the theory that (for women with mild-to-moderate
anaemia) the placenta and fetus have a special affinity for iron in the
mother’s circulation, and iron is transported through the placenta
irrespective of the concentration
gradient.12
Some studies have shown similar results, with the fetus
gaining iron stores independently of maternal iron status. Sturgeon demonstrated
that fetal-cord-blood haemoglobin levels were similar in anaemic and non-anaemic
mothers.10 Furthermore, Cantwell et al showed
that mothers who were given adequate and less-than-adequate iron therapy during
pregnancy had babies with similar cord-blood haemoglobin
levels.11 Turkay et al found no correlation
between maternal haemoglobin and ferritin at 16 and 34 weeks’ gestation
and newborn haemoglobin parameters.12 Bhargava
et al found maternal iron depletion did not adversely affect newborn haemoglobin
levels.14
However, it appears that the relationship between the mother
and fetus regarding the acquisition of iron is more complex, with other studies
documenting a correlation between maternal iron status and that of the fetus or
newborn infant. Sisson and Lund15 and Nhonoli
et al16 found that the newborn of iron
deficient mothers had significantly lower levels of haemoglobin and iron in the
cord blood. Singla et al found that maternal haemoglobin had a linear
correlation with haemoglobin and iron levels in the cord blood and placental
tissue.17 Fenton et
al18 and Milman et
al13 found that maternal ferritin correlated
with cord and newborn ferritin levels, respectively. Rusia et al found that
maternal haemoglobin did not correlate with cord blood haemoglobin, but maternal
ferritin and haemoglobin were found to correlate positively with cord
ferritin.19
This present study suggests that, in our population of Maori
and non- Maori mothers, iron parameters taken at the end of the third trimester
of pregnancy did not significantly affect fetal iron parameters. However, when
separating for ethnicity, Maori mothers had significantly lower haemoglobin
values and Maori infants had significantly lower cord ferritin values compared
to non-Maori. It is possible that these parameters may be linked and related to
higher rates of anaemia in Maori infants. This possibility would require
clarification with further research.
Author information:
Diane P. Emery, Paediatric Registrar; David M. J. Barry, Paediatric Consultant,
Paediatric Department, Hastings Memorial Hospital, Hastings, Hawke’s
Bay.
Acknowledgements: We
thank the Hawke’s Bay Medical Research Foundation (for their support in
funding this study), Mrs Elizabeth Robinson, Biostatistician (or her advice
regarding statistical analysis), and the staff of the Obstetric Unit and the
Operating Theatre of Hastings Memorial Hospital (for their assistance with the
study).
Correspondence:
Diane P. Emery, 26 Umere Crescent, Ellerslie, Auckland. Email:
d.emery@auckland.ac.nz
References
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| | Current
issue | Search journal |
Archived issues | Classifieds
| Hotline (free ads) Subscribe | Contribute | Advertise | Contact Us | Copyright | Other Journals |
|