Main body of text:
This study assessed the prevalence of anaemia in a mixed metropolitan
and urban setting in in the UK during first trimester of pregnancy to
draw conclusions around managing iron deficiency.
The provision of healthcare has to adapt to new and innovative ways of
delivering evidence-based good care in view of the SARS-CoV-2 pandemic.
One area where this could be realised is in the management of iron
deficiency particularly in pregnancy. There are excellent UK-based
guidelines which need not be replaced but rather adapted in the light of
current pandemic1.
Iron deficiency is common, particularly in women of child bearing age
predominantly around menstrual blood loss and poor oral intake of
iron-rich foods2. This issue becomes more pronounced
during pregnancy with historically around a quarter of UK pregnancies
associated with anaemia3. Whilst there is an
international definition of anaemia during pregnancy, it is acknowledged
that further work is required to validate them1.
Worldwide the commonest cause of anaemia is iron deficiency. The
pathognomonic hallmark is a low serum ferritin, usually
<15mcg/l. In addition a serum ferritin of <30mcg/l
indicates low iron stores4. Given that around 800mg of
body iron is required for foetal development women either iron deficient
and anaemic, iron deficiency without anaemia, or low iron stores without
anaemia will to a decreasing extent risk running out of iron stores and
becoming more anaemic during pregnancy. Even those with normal Hb and
iron stores risk iron deficiency later in pregnancy.
Whilst post diagnosis treatment with oral iron still remains appropriate
there is an ongoing possibility that such women may need intravenous
iron or blood transfusion around delivery. In light of the SARS-CoV-2
pandemic this should be avoided if at all possible since it involves
therapy within a healthcare setting. Under the current pandemic
circumstances a more proactive approach is required.
We studied 1715 pregnancies during the 5 months of November and December
2018, March, April and May 2019. We looked at Haemoglobin (Hb)
estimation at those booking prior to 13 weeks gestation. Our population
has a very low carriage of haemoglobinopathy.
All full blood counts and serum ferritin assays were assessed on an
Abbott Alinity hq and Architect analysers respectively.
148 (8.6%) women had Hb concentrations below 120g/l with 25 (1.5%)
below 110g/l. Median Hb was 132g/l; minimum 90g/l, maximum of 160g/l.
The 95% lower limit confidence level was 116g/l.
Guidance suggests that Hb values >110g/l are adequate in
the first trimester1. Our data shows the lower limit
of normal in our cohort was 116g/l. Hypothesising that the first
trimester is not physiologically dissimilar to a pre-pregnant state we
chose Hb<120g/l as our defining threshold for anaemia. Similar
challenges of the definition of peri-operative anaemia in pregnant women
also suggest targeting a higher Hb may be more
appropriate5.
We further assessed the outcome in pregnancies in November, December and
March in those pregnancies where the booking Hb at less than 13 weeks
gestation was below 120g/l. Ninety of 1001 women during these months had
Hb <120g/l giving a 9% incidence of anaemia by our
definition. Of 81 evaluable cases Hb fell from booking to 28 week
gestation by a median of 8g/l (range +39 to -27g/l) with 33 (41%)
dropping by 10g/l or more. No data on iron supplementation was
collected.
Of the women with Hb <120g/l the average MCV and MCH were
87.5fl and 29pg respectively. Of these 17% had an MCV <80fl,
and 27% had an MCH <28pg. Most therefore had normal red cell
indices.
In the 3 months assessed only 16 women (18%) had their serum ferritin
(SF) checked with a median value of 6.5mcg/l (range 3 to 45). Thirteen
of 16 women had SF below 30mcg/l. Although only a few cases, we saw an
average fall in Hb of 3.5g/l (median rise of 2g/l, range -22g/l to
+15g/l). One assumes that in those pregnancies found to have a low serum
ferritin, iron supplementation was given. Of note the serum ferritin was
only requested at booking if the MCH was found to be <27pg (in
all but one patient who had a normal MCH) as part of the United Kingdom
National Sickle cell and Thalassaemia screening programme.
Only 4 pregnancies were associated with blood transfusions.
Whilst we cannot show that low Hb at booking predicts for a transfusion
requirement we can show that the incidence of anaemia in our first
trimester population is around 9%. We suggest that Hb values below
120g/l in the first trimester are not physiologically acceptable. For
our cohort there is a fall in Hb between booking and 28 weeks of 8g/l
which would generally be the accepted norm. The fall is less in the
small number of cases that were shown to have low SF and therefore
likely treated.
In the light of the current SARS-CoV-2 pandemic our study suggests that
for all women at booking with Hb less than 120g/l we should offer low
dose iron supplementation even if they have a normal serum ferritin. If
the serum ferritin is below 30mcg/l irrespective of the Hb iron should
also be offered. This means that at least 9% of women will be given
iron therapy at booking on the basis of their Hb alone. Using a low MCV
or MCH to decide if serum ferritin testing is required seems to be
wholly inappropriate since both MCV and MCH are in the majority normal
in pregnant women at booking even with iron deficiency.
What do we suggest?
1) Universal screening for iron deficiency in the first trimester and
treating cases with oral iron. We suggest that all women at booking who
have Hb <120g/l or have low iron stores (serum ferritin
<30mcg/l) at booking start low dose oral iron.
Rationale: Most anaemia in pregnancy is due to iron deficiency and there
will always be more demand on iron stores as pregnancy progresses.
Pairing the full blood count with a serum ferritin avoids the risk of
iron supplementation in persons with potential iron overload indicated
by a raised serum ferritin. Although tolerability and compliance are
potential issues, using a low dose is potentially better
tolerated6. Starting early improves the chances of
having sufficient stores later in pregnancy and attempts to reduce the
need for intravenous iron. Low dose oral iron is typically ferrous
sulphate 200mg alternate daily.
2) Once started on oral iron there is no requirement to monitor the
effect until repeat testing at 28 weeks occurs unless the booking Hb is
less than 100g/l
Rationale: Whilst this seems at variance with standard practice where
one would look to always gauge response after 2-4 weeks, the intention
is to limit contact with the healthcare system as much as possible.
Concerns around not monitoring could be met by telephone contact about
symptoms and compliance or performing a full blood count and
reticulocyte count on those felt to be at greater risk such as when the
booking Hb is less than 100g/l.
3) Only women with persistent iron deficiency despite oral iron should
be considered for intravenous iron. Iron deficiency at or beyond 34
weeks and Hb<70g/l would be a strong indication for
intravenous iron regardless of prior oral iron
intake1. It should be considered for similar cases
with Hb <100g/l but alternatives should be considered if
symptoms allow for those persons iron deficient with Hb
>100g/l.
Rationale: One major aim is to reduce the need for intravenous iron for
only those where all other choices have been explored. Alternative iron
preparations may be considered, but ultimately intravenous iron may be
the only option. Initial iron therapy orally is appropriate but recourse
to intravenous iron is advised if severely iron deficient anaemic
(Hb<70g/l) or there is insufficient time for oral iron to work
or be compliant with.