This page is aimed at women in the UK who are considering a home birth, but will also be relevant to anyone investgating anemia in pregnancy. It discusses when a woman is at higher-risk, and when supplements may be useful.
This page in a nutshell:
What's the worry about anaemia?
Blood tests for anaemia - Hb, MCV, ferritin
What's wrong with taking iron supplements even if you don't need them?
How can I raise my iron levels?
Does a low Hb count mean you're more likely to haemorrhage?
Arranging a homebirth when you have low Hb
The Third Stage of Labour, and Your Baby
One of the routine blood tests in pregnancy is for iron-deficiency anaemia. This is because pregnant women need more iron than non-pregnant women - the baby needs iron, and if you don't have enough iron for both of you, your red blood cells may not be able to carry enough oxygen around your body. This can make you feel tired and sometimes breathless, as well as increasing the risk of a low birthweight baby.
The main concern for labour is that, if you are genuinely iron-deficient, your blood will not be able to carry as much oxygen as it should. You are no more likely to haemorrhage, but IF you were to suffer a severe haemorrhage, you might be in more danger than a woman whose blood was able to carry more oxygen.
It is partly for this reason that most hospitals recommend a hospital birth if you have iron-deficiency anaemia - so that you can have quick access to emergency support if you have a severe haemorrhage.
Women who are iron-deficient are thought to be at higher risk of premature labour, although some sources dispute this [Lao, 2000]. However, this seems less relevant to the home birth issue, since most women would change their plans and choose hospital birth when faced with premature labour. Another concern is the possibility of a low birthweight baby, but this is something which can be screened for separately. If you are concerned about your baby's growth, please see 'Homebirth with a suspected small baby'. Both prem labour and low birthweight babies are issues which you can consider if they start to affect your pregnancy. Therefore it seems that the main concern for women with anaemia who are considering a homebirth, is what would happen if she had a severe haemorrhage - see the discussion of PPH risks below.
Note that these are some of the risks of genuine iron-deficiency anaemia. However, many women who have a low Hb level, which is the inital screening test for anaemia, will not actually be iron-deficient; a low haemoglobin level frequently just means that your blood has become well diluted in pregnancy, which is a good sign. This is called ' normal haemodilution of pregnancy'.
Haemodilution literally means dilution of the blood. In pregnancy, your overall blood volume increases by up to 50%, but because your red blood cells don't increase in total volume by as much as the plasma, the red blood cells are spread more thinly. In some women, this 'dilution' is stronger than others - you can see from the extract below that estimates of the different increases vary according to which study you look at. In this situation, your haemoglobin levels might well be lower than average, but you would not see signs of iron deficiency such as a low MCV or Serum Ferritin, which are explained below.
Here's an explanation aimed at family doctors, from the UK's GP Notebook:
- there is an increase in the total blood volume, the plasma volume and the red cell volume during pregnancy. The total blood volume increases by about 30-40% by about 34 weeks of pregnancy
- there is a relative increase in plasma with respect to red cells - 45% increase in plasma versus 18% increase in red cells respectively. This imbalance causes a haemodilution
Normal haemodilution is a good sign, and is not something that iron supplementation can 'cure'.
Writing in the Journal of Family Practice, Alper and colleagues found that:
Standard obstetrical practice has included screening for anemia and the provision of iron supplements to anemic patients. This approach has been based on assumptions about anemia and iron deficiency that are not supported by the literature.
"In our population of prenatal patients with anemia, only 54% had an iron deficiency. Diagnostic and therapeutic approaches to screening for anemia in pregnancy should be reconsidered and further evaluated to avoid unnecessary iron therapy."
The first 'screening' test for anaemia is the haemoglobin count, or Hb level. Until recently this was often the only test for anaemia which would routinely be given, which is perhaps why there is a 'hangover' effect and not all midwives are up to speed with the other tests.
The following tests help us to tell the difference between normal haemodilution and iron-deficiency anaemia.
Here is more on haemoglobin from patient.co.uk:
"Red blood cells are made in the bone marrow, and millions are released into the bloodstream each day. A constant new supply of red blood cells is needed to replace old cells that break down. Red blood cells contain a chemical called haemoglobin. Haemoglobin binds to oxygen and takes oxygen from the lungs to all parts of the body.
To constantly make red blood cells and haemoglobin you need a healthy bone marrow and nutrients such as iron and certain vitamins which we get from food."
The Hb result states how much of your blood, by weight, is haemoglobin. The result is normally given as grams per decilitre (100ml), or g/dLL, but it may also be given as grams per litre.
What should your Hb level be?
Mayes' Midwifery textbook says:
"The World Health Organization (1979) considers anaemia to be present in the pregnant woman when haemoglobin is 11g/dl or less. More arbitrary levels may be decided locally and usually range between 10 and 10.5g/dl"
In the UK, the most common definition of mild anaemia is an Hb level of 10 g/dl (100g per litre of blood) or less. Severe anaemia is usually defined internationally as 7g/dl (70g/L) or less, but to complicate matters, some studies define this as 'moderate' anaemia, and 'severe' as 4.7g/dll or less.
In the UK, the NICE Guidelines on Intrapartum Care state that a haemoglobin level of less than 8.5g/dLL at the start of labour suggests a woman is at increased risk and should be advised to give birth in an obstetric unit rather than at home or a low-risk centre, and women with Hb of 8.5 - 10.5g/dl should have 'individualised assessment' to help them plan their place of birth (p11).
MCV is a measure of how 'fat' or 'skinny' your red blood cells are, ie whether they really are deprived of iron or not.
From Lab Tests Online UK:
"Mean corpuscular volume (MCV) is a measurement of the average size of your red blood cells (RBCs). The MCV is elevated when your RBCs are larger than normal (macrocytic), for example in anaemia caused by vitamin_b12 deficiency. When the MCV is decreased, your RBCs are smaller than normal (microcytic), such as is seen in iron deficiency anaemia or thalassaemias. "
Here's an extract from the NHS patient information database on Anaemia in Pregnancy:
Investigations Hb < 11.0g/dl 3
MCV (mean cell volume): if < 76fl then probable cause is iron deficiency ...
Normal MCV (76-96fl) with low Hb is typical of pregnancy.
MCV doesn't tell the whole story, because it is affected by other things. For example, vitamin B12 deficiency can make your MCV higher than average, so it is possible that this could mask an iron deficiency. MCV is part of the Full Blood Count, which gives a good overall picture of your blood's health.
The serum ferritin, or 'ferritin', test measures your body's iron stores. A healthy person has reserves of iron in the body so that you do not become anaemic if you have a short period where your diet does not provide enough iron. If you have genuine iron-deficiency anaemia then you would expect your body to have very little stored iron. On the other hand, if iron stores are high and diet adequate, then taking iron supplements is unlikely to be effective.Alper and colleagues published a very detailed article on using ferritin levels to determine iron-deficiency anaemia in pregnancy, in the Journal of Family Practice (2000). It says:
Lab Tests Online UK says:
"Ferritin levels are considered the gold standard for the diagnosis of iron-deficiency anemia in pregnancy"
If a blood count indicates that your haemoglobin and haematocrit are low, especially if your red blood cells are smaller and paler than normal ('microcytic' and 'hypochromic'), this indicates that you have anaemia due to iron deficiency. Ferritin and other iron tests can be used to confirm the diagnosis.
What does the test result mean?
Ferritin levels are low in long-term iron deficiency, or if your body's protein levels are very low, as in some cases of malnutrition.
If serum ferritin is the 'gold standard', why don't we just test for that and forget Hb and MCV? Because ferritin levels can fluctuate for other reasons. In particular, they can rise in women with pregnancy-induced hypertension or pre-eclampsia, both of which are relatively common in the third trimester [Lao, 2000]. So serum ferritin can't be taken in isolation, but together with Hb and MCV levels, it can give you a good picture.
There are other reasons for anaemia besides iron deficiency, eg inherited conditions like sickle-cell disease or thalassemia - your midwife would probably already have considered these possibilities. Nonetheless it's worth checking - if you find out your Hb level and MCV, and your MCV is normal, then you could ask your midwife why she thinks you are iron-deficient, or indeed higher-risk in any way.
Severe anaemia is a major problem in the developing world and it increases the risk that a baby will be born prematurely, or have a low birthweight. The risks are highest when the mother is anaemic in the first trimester of pregnancy as this suggests that her nutritional status before pregnancy was poor - her low Hb levels cannot be caused by her blood volume expanding ('haemodilution of pregnancy') because blood volume will not have expanded greatly at this stage. If a woman is anaemic in the first trimester because of poor nutrition, it may also suggest that she will not have a good diet or healthcare during her pregnancy. Many women in the developing world who suffer from anaemia may not simply be deficient in iron, but may also have malaria, sickle-cell anaemia or other blood diseases ('haemoglobinopathies') and some of the research into anaemia in pregnancy looks at different categories individually. However, you will occasionally see attention-grabbing quotes saying that women with anaemia have significantly higher rates of stillbirth. Where references are given, it often turns out that the source is a study looking at severely anaemic women in the developing world - not necessarily relevant to a woman in the UK with only mild anaemia.
There seems to be no good evidence that a woman in the developed world with an Hb level of 9 or 10, and no other complicating factors, is at any increased risk of complications in labour, nor her baby at increased risk after birth. For instance, in a study of Swedish women, Stephansson (2000)found that anaemia was not significantly associated with risk of stillbirth in multivariate analyses, although high haemoglobin (146 g/l or more) was associated with an increased risk of stillbirth. Several studies have now found that the best outcome for the baby, in terms of avoiding low birthweight and prematurity, arises when the mother is actually mildly anaemic by standard definitions. For instance, Malhotra et al (2002) compared outcomes for women with 'normal' blood (Hb above 11g/dll) with those for women with mild anaemia (9 - 10.9 g/dll), moderate and severe anaemia (severe being Hb lower than 7g/dll). They found that:
"Women in Group II (mild anaemia) had lowest number of low birth weight and IUGR babies, no stillbirths and neonatal deaths, lowest induction and operative delivery rates. ... Mild anemia fared best in maternal and perinatal outcome. Severe anemia was associated with increased low birth weight babies, induction rates, operative deliveries and prolonged labor."
"A Guide to Effective Care in Pregnancy & Childbirth (2nd Edition) " by Enkin, Keirse, Renfrew and Neilson, is the UK's 'gold-standard' textbook on evidence-based maternity care and is generally respected by all midwives and obstetricians. Here's what it says on this subject:
The normal haematological adaptations to pregnancy are frequently misinterpreted as evidence of iron deficiency that needs correcting. Iron supplements have been given with two objectives in view: to try to return the haematological values towards the normal non-pregnant state, a strange objective when millions of years of evolution have determined otherwise, and to improve the clinical outcome of the pregnancy and the future health of the mother. The first objective can certainly be accomplished; the key question is whether or not achieving the "normalized" blood picture benefits the woman and her baby. Routine iron supplementation raises and maintains serum ferritin above 10 microgram/litre and results in a substantially lower proportion of women with a haemoglobin level below 10 or 10.5 grams per cent (below 6-6.5 mmol/litre) in late pregnancy. Routine folate supplementation as a haematinic after the first few weeks of pregnancy substantially reduces the prevalence of low serum and red cell folate levels, and of megaloblastic haematopoiesis.
As yet, neither iron nor folate supplementation after the first trimester have shown any detected effect on the following substantive measures of maternal or fetal outcome: proteinuric hypertension, antepartum haemorrhage, postpartum haemorrhage, maternal infection, preterm birth, low birthweight, stillbirth, or neonatal morbidity. Women do not feel any subjective benefit from having their haemoglobin concentration raised.
A possible advantage claimed for a high level of haemoglobin in pregnancy is that the woman would be in a stronger position to withstand haemorrhage. There is no evidence to support this claim. Indeed, as a low haemoglobin in healthy pregnant women generally implies a large circulating blood volume, it is at least possible that women with a low haemoglobin might better withstand a loss of blood....
Whether routine iron supplementation causes any harm in well-nourished communities is still unclear, but it is clearly wasteful. The evidence suggests that, except for genuine anaemia, the best reproductive performance is associated with levels of haemoglobin that are traditionally regarded as pathologically low. There is cause for concern in the findings of two well-conducted trials that iron supplementation resulted in an increase in the prevalence of preterm birth and low birthweight. Perhaps there is an adverse effect on fetal growth due to the increased viscosity of maternal blood that follows the iron-induced marcrocytosis and increased haemoglobin concentration, which may impede uteroplacental blood flow.
An individual's haemoglobin concentration depends much more on the complex relation between red-cell mass and plasma volume than on deficiencies of iron or folates. The advent of electronic blood counters has given an opportunity for more appropriate criteria to be applied to the diagnosis of anaemia. Mean cell volume may be the most useful; it is not closely related to haemoglobin concentration and declines quite rapidly in the presence of iron deficiency. A low haemoglobin without other evidence of iron deficiency requires no treatment.
There are questions over whether unnecessary iron supplementation may be harmful in pregnancy. Around 40% of women who are prescribed iron supplements are unable to tolerate them because of the severity of side-effects. It is possible that unnecessary supplementation may be harmful for the baby. [Lao, Tam and Chan, 2000, and see also Alper, 2000 for further refs]. Recently there has also been high-quality research which found that pregnant women who were not iron-deficient had a significantly higher risk of developing high blood pressure if they were given iron supplements (as ferrous sulphate). There was also a higher risk of having a low-birthweight baby [Ziaei et al, 2007 and RCOG press release]. Dietary experiments with pregnant rats have also shown harmful effects for both mother and offspring [Ward et al, 2003]. It is important to note that these studies only looked at mothers who had a 'normal' haemoglobin level and thus their results may not be applicable to women with lower Hb. We do not know in what circumstances the benefits of iron supplementation outweigh the risks, because the risks appear not to have been well studied. It is likely that it was considered unethical or impractical to include women with lower Hb in the study group because standard management is to supplement with iron where low Hb is found. However, now that it is relatively cheap and easy to obtain more specific blood tests, it is to be hoped that researchers may start to consider women who have lower Hb but who are not iron-deficient. The Cochrane Review of evidence on treatment for iron-deficiency anaemia in pregnancy found that:
..it is unclear if women and babies are healthier when women are given iron for anaemia during pregnancy. It also remains unclear what the effects of treatments given by different routes and in different populations are; therefore, it is not possible to draw a well-informed balance of benefits and harms for the differing levels of severity of anaemia.
Michel Odent, obstetrician and natural birth supporter, writes in an article on the value of antenatal tests:
The regrettable consequence of routine evaluation of hemoglobin concentration is that, all over the world, millions of pregnant women are wrongly told that they are anemic and are given iron supplements. There is a tendency both to overlook the side effects of iron (constipation, diarrhea, heartburn, etc.) and to forget that iron inhibits the absorption of such an important growth factor as zinc (18). Furthermore iron is an oxidative substance that can exacerbate lipid peroxidation (free radicals) and might even increase the risk of pre-eclampsia (19).
Lots of women have a diet which is plentiful in iron, but still for some reason do not absorb enough of it. If you are convinced that your iron level is genuinely low then it is worth taking action to increase it. Before you do this, however, please read 'Is the problem really iron deficiency?'. If you are not deficient in iron then the best-case scenario is that taking iron supplements will give you expensive bowel movements; however, if you take prescribed iron supplements then you may end up with unpleasant side-effects including nausea, constipation, etc..
The iron supplement usually prescribed on the NHS is ferrous sulphate, because it's a very cheap way of getting a high dose of iron. You can also get ferrous gluconate and ferrous fumarate on prescription, which may cause fewer side-effects.
The British Society of Gastroenterology guideline on iron deficiency anaemia explains:
“Iron therapy Treatment of an underlying cause should prevent further iron loss but all patients should have iron supplementation both to correct anaemia and replenish body stores (B). This is achieved most simply and cheaply with ferrous sulphate 200 mg twice daily. Lower doses may be as effective and better tolerated and could be considered in patients not tolerating traditional doses. Other iron compounds (e.g. ferrous fumarate, ferrous gluconate) or formulations (iron suspensions) may also be tolerated better then ferrous sulphate. Ascorbic acid (250–500 mg twice daily with the iron preparation) may enhance iron absorption. We recommend that oral iron is continued until three months after the iron deficiency has been corrected so that stores are replenished.” 
Two iron supplements which are popular with pregnant woman are Floradix and Spatone. Both can be bought from health food stores like Holland and Barrett, and often from Boots, as well as from plenty of online retailers. Midwives and mothers on the Homebirth UK egroup have reported very rapid results from Spatone raising Hb levels.
Spatone has a section on its website for health professionals which cites some impressive research showing that it is absorbed incredibly quickly into the bloodstream and is extremely effective at raising blood Hb levels. It's actually only a form of naturally iron-rich water - even tastes like rusty water.
The real bonus of this, and other forms of 'natural' iron like Floradix, is that they don't usually cause any gastric symptoms; the NHS iron supplements are cheap and nasty, and while they give you a massive whack of iron, it's in a form which is hard for your body to absorb. The unused portion can cause diahorrhea, constipation, nausea, you name it - which is why there is such a market for less offensive alternatives.
There are four studies on Medline of the effectiveness of Spatone and they all seem to confirm the manufacturer's claims, which you can find on the 'health professionals' section of its website (www.spatone.co.uk).
Some GPs have prescribed Spatone for pregnant women on the NHS, if they suffer adverse symptoms from the other iron supplements.
All iron supplements are allegedly most effective when taken with vitamin C as it helps absorption of iron (eg take in/with a glass of orange juice), and avoid tea as tannins hinder absorption.
I've trawled through Medline, the international database of medical research, and found nothing on correlations between low Hb antenatally and risk of haemorrhage. Not surprisingly, there are papers showing that a low postpartum Hb level is associated with having had a PPH. This is like saying that cars with dents are likely to have been involved in accidents than cars without dents. However, that does not mean that your car is more likely to be involved in a crash in future, just because it has a dent already!
Another view, less commonly heard, is that a woman can be said to have had a PPH if her Hb levels fall below a certain level after the birth. Thus she might lose only 100ml of blood, but still be said to have haemorrhaged because her postpartum Hb level was, say, 8 - even though it was, say, 8.5 before the birth. This is not the way most women think of postpartum haemorrhage, and if we are trying to screen out emergency transfers to hospital, it is probably not most relevant.
The extract from 'A Guide to Effective Care in Pregnancy and Childbirth', above, explains that Hb levels in pregnant women are generally lower than in non-pregnant women, but that this does not mean that low Hb levels are a problem. Iron supplements can normally raise Hb levels in pregnant women to the 'normal' level for non-pregnant women, but there is no evidence that raising the Hb levels in this way benefits mother or baby at all.
The UK's NICE Intrapartum Care Guidelines include women with Hb of 8.5g/dl in their list of women at higher risk of PPH (p254), but the supporting text (p250) states that only one study was included on this topic and it found no difference in rates. I assume that NICE included women with low Hb in this category because of the possible increased dangers to them of severe blood loss, as mentioned above:
"A cohort study was conducted in New Zealand in 1996 comparing haemoglobin levels at 4 weeks prior to birth on PPH (blood loss 600 ml or greater within 24 hours of birth).578 [EL = 2-] Although the study reported no difference, the analysis did not control confounding factors and hence was inconclusive."
Some years ago, I asked doctors and medical students on sci.med.obgyn newsgroup if there was any evidence that low Hb levels might increase the chances of post-partum haemorrhage. These were the responses:
I am studying obstetrics at the moment... I know of no evidence to this effect. The mechanisms of PPH are uterine atony, lacerations, and retained products. None of these should be affected by anaemia, though I guess a general aplasia of marrow could lead to thrombocytopenia as well as anaemia.
The reason why haemoglobin levels are low is because the plasma volume increases, while erythrocyte production doesn't increase so much. Hb levels are measured as a concentration, not as an absolute amount. Thus there is a normal 'anaemia' associated with pregnancy, which causes no problems. Of course one can also get folate/iron deficiency or malnutrition which causes a genuine anaemia.
This myth has been around a while...I've never seen any evidence...
It also depends on definition...if your definition of PPH is need for transfusion, then maybe it's true since if you start with a lower Hgb, you can suffer less blood loss before you need a transfusion. If your definition is strictly how much you bleed, then starting Hgb is irrelevant...
Adam Newman, MD
(Postpartum haemorrhage is defined in most countries as blood loss over 500mls, but some midwives and obstetricians prefer to look at the condition of the individual woman, and consider her blood loss to have been excessive if she is showing syptoms suggesting that, regardless of how much her measured blood loss is. While this is good for individualised care, it's not helpful if you want to collect data, make comparisons, and so on!)
It seems that it is probably irrelevant to 'risk out' a woman from home birth because of her Hb level. Such advice is probably due to an incorrect understanding of the implications of low Hb levels.
Some people suggest that, while the actual risk of haemorrhage doesn't increase when Hb levels are low, if a mother with low Hb does haemorrhage, she might find it harder to recover. This reflects the point made above by Dr Newman. However, there appears to be little evidence to support even this. For example, in the section from 'A Guide to Effective Care in Pregnancy & Childbirth' by Enkin, Keirse, Renfrew and Neilson copied below,
"A possible advantage claimed for a high level of haemoglobin in pregnancy is that the woman would be in a stronger position to withstand haemorrhage. There is no evidence to support this claim. Indeed, as a low haemoglobin in healthy pregnant women generally implies a large circulating blood volume, it is at least possible that women with a low haemoglobin might better withstand a loss of blood. "
Of course, any mother suffering a serious haemorrhage would be transported to hospital immediately, where she could receive a blood transfusion. Transfer times to hospital should be taken into account when making any decision about home birth, but when transfusions are given, it is often a day or more after the birth, rather than as an emergency measure.
An important consideration for women who are worried about blood loss is that there is less risk of severe blood loss with a homebirth. This is largely because starting off at home reduces your risk of ending up with an operative delivery, either cesarean or forceps or ventouse - all of which are associated with significantly increased blood loss. Therefore, if you are genuinely iron-deficient and are struggling to get your levels up before the birth, homebirth could be said to have a protective effect, and is a positive step to reduce your risk of haemorrhage.
This website has more information on Postpartum Haemorrhage and Homebirth - how likely it is, and what happens if you have a PPH at home. You can find references for homebirths and PPH risks there.
If your midwife or doctor maintains that a low Hb level makes you an unsuitable candidate for home birth, please consider asking them for evidence and citations to support their claims. I would be very interested to hear of any research which backs it up. I've been looking for ten years now and nothing convincing has been forthcoming!
If you make an informed choice to continue with homebirth plans 'against advice' then it can be helpful to write a letter to the Head of Maternity or the Community Midwifery Manager at your hospital, copied to your community midwives. Here is a sample letter:
Dear Community Midwifery Manager,
I am booked for a home birth under the care of Team X, and my estimated due date is (date).
Midwife Z has informed me that your guideline is to recommend hospital birth whenever a woman's haemoglobin count is below 10 g/dLL, and my count at the last test was (result).
I am writing to inform you that I have looked into the matter and have decided to continue with my homebirth plans. I believe that the risks of hospital birth in my situation outweigh the benefits at the moment. If my circumstances change then I will of course consider the situation again. I appreciate the advice of my midwives, but I am prepared to take responsibility for my own decisions. I am informing you of my decision now so that you have plenty of time to make the necessary arrangements, to ensure that staff are available to attend my birth at home.[If you want to, and fully understand the subject, you could add a paragraph here giving more details of your individual circumstances. You do not need to justify your decision to give birth at home, or to explain it, or to 'persuade' anyone to 'allow' you a homebirth. However, you may choose to discuss it further, both to make sure that you are fully informed, and perhaps to help your midwives be more open-minded with other women! If you show that you understand the subject it may reassure your midwives - they may be concerned that you might blame them if you went ahead with a homebirth, and, unlikely though it is, had a heavy bleed, and then needed to transfer to hospital afterwards. I believe it is important, if you want to get involved in a technical discussion, that you understand all the terms involved and feel confident using and discussing them. If you don't feel confident, it may be better to avoid using them!]
So - the sort of thing you might add here could be:
I have been given the results of my full blood count and my Mean Cell Volume is 88. This is well within normal limits of 80-100 and therefore there is no reason to suppose that I am iron-deficient. There have been no abnormal results suggesting ill health of any kind. I believe that my Hb level of 9.5 g/dLL is accounted for by normal haemodilution of pregnancy and, following the guidelines in A Guide to Effective Care in Pregnancy and Childbirth, that I am not at any increased risk, nor in need of any treatment, as a result.
Finally, if you are genuinely iron-deficient, you may wish to think about your options for the third stage of labour - the delivery of the placenta.
You may find that you are encouraged to have a managed third stage, where you are given an injection to assist the delivery of the placenta and hopefully to reduce the averge blood loss. See The Third Stage for your options. Side-effects of this can include sudden nausea, headache and blood pressure fluctuations, so many women who are aware of this risk, prefer to wait and see how the third stage progresses and to have the injection only if their blood loss is worrying.
If you do decide to have a managed third stage, please give serious consideration to the issue of when the baby's cord will be clamped. In many places it is still routine to give the injection as the shoulders are being born, and to clamp the cord immediately after birth. This results in up to a third of the baby's blood volume being trapped inside the placenta and cord, and it is lost with the placenta; neither baby nor mother can use it.
An alternative is to wait around three minutes for the cord to finish pulsating, before clamping and giving the injection. This means that the full complement of blood has been transfused to the baby. This is particularly relevant if the mother is iron-deficient, because if her iron stores are low, then the baby's will be too. The baby who is born with low iron stores is at risk of anaemia in its first year, and can ill-afford to have up to a third of its blood volume thrown away with the placenta.
If the cord is allowed to finish pulsating, the baby gets its full share of placental blood. Any excess red blood cells are broken down and the iron appears to be scavenged for the baby's iron stores. Iron-deficiency anaemia is much more common in babies whose cords were clamped early, throughout the first year. You can read more about this, and find references, on The Third Stage page.
For more discussion of these issues, and suggestions of ways to raise your Hb levels through diet and supplements, see the Association of Radical Midwives archive on the Third Stage of Labour.
Merck medical manual - chapter on Anemia in Pregnancy
Anaemia in Pregnancy - patient.co.uk information sheet
Iron-Deficiency Anaemia - patient.co.uk information sheet.
Lab Test Online UK - "A clinical resource on clinical lab testing, from the professionals who do the testing" - explains how and when different tests are used, and what the results mean.
Anemia: When Is it Not Iron Deficiency?: Differential Diagnosis of Anemia by RBC Indices and Biochemical Markers
Very technical, but well-referenced, Medscape article.
British Society of Gastroenterology. Guidelines for the management of iron deficiency anaemia. 2005.
NHS Clinical Knowledge Summary (formerly Prodigy) on iron-deficiency anaemia
Royal College of Obstetricians and Gynaecologists press release on risks of iron supplementation in non-anaemic pregnant women.
(backup copy on this site)
The Rise of Preconceptual Counseling Vs The Decline of Medicalized Care in Pregnancy - Michel Odent MD
And see also links in the References, below.
JAMA. 2000 Nov 22-29;284(20):2611-7.
Maternal hemoglobin concentration during pregnancy and risk of stillbirth.
Stephansson O, Dickman PW, Johansson A, Cnattingius S.
PMID: 11086368 [PubMed - indexed for MEDLINE]
Malhotra et al (2002):
Int J Gynaecol Obstet. 2002 Nov;79(2):93-100.
Maternal and perinatal outcome in varying degrees of anemia.
Malhotra M, Sharma JB, Batra S, Sharma S, Murthy NS, Arora R.
PMID: 12427391 [PubMed - indexed for MEDLINE]
Using Ferritin Levels To Determine Iron-Deficiency Anemia in Pregnancy
Journal of Family Practice , Sept, 2000
Brian S. Alper, Roger Kimber, Anuradha Kudumala Reddy
Lao, Tam and Chan 
Human Reproduction, Vol. 15, No. 8, 1843-1848, August 2000
© 2000 European Society of Human Reproduction and Embryology
Third trimester iron status and pregnancy outcome in non-anaemic women; pregnancy unfavourably affected by maternal iron excess T.T. Lao1,3, K.-F. Tam2 and L.Y. Chan1,2
Ziaei et al, 2007:
BJOG. 2007 Jun;114(6):684-8
A randomised placebo-controlled trial to determine the effect of iron supplementation on pregnancy outcome in pregnant women with haemoglobin > or = 13.2 g/dl.
Ziaei S, Norrozi M, Faghihzadeh S, Jafarbegloo E.
Royal College of Obstetricians and Gynaecologists press release on risks of iron supplementation in non-anaemic pregnant women.
Ward et al, 2003
Iron Supplementation During Pregnancy- A Necessary or Toxic Supplement?
Roberta J. Ward, Stephanie Wilmet, Rachida Legssyer, and Robert R. Crichton
Bioinorg Chem Appl. 2003; 1(2): 169–176.
Cochrane Review of evidence on treatment for iron-deficiency anaemia in pregnancy
A note on spellings: 'Anaemia' is the UK spelling for what, in US English, is 'anemia'; likewise here we use 'Haemoglobin' rather than 'Hemoglobin' . Search engines may be slightly confused by this, so I have varied spellings through the text. The occasional Americanism is not a typo - it's so that Google can still rank the page effectively.
Home Birth Reference Page