Can a healthy diet help reduce the risk of developing preeclampsia during pregnancy?

One of my close friends is pregnant (I am very excited)! We were chatting about pregnancy health and the topic of preeclampsia came up. Recently a study(1) was published which suggests that increasing the amount of fibre eaten during early pregnancy may help to reduce the risk of preeclampsia developing later. I thought now was as good time as any to look into this complex topic further!

Preeclampsia is a serious condition also known as: pregnancy-induced hypertension (PIH); proteinuric gestational hypertension; and toxaemia of pregnancy. It is a form of high blood pressure (hypertension) that develops in conjunction with water retention (oedema) and/or excess protein in the urine (proteinuria). Around 3% of all pregnant women suffer from preeclampsia each year and this condition is the principal cause of maternal death in the UK. Around 10 mothers and 1000 babies die each year as a result of the effects of preeclampsia and the condition is also the most common reason for elective (often early) delivery. Usually preeclampsia occurs between the 20th week of Pregnancy and the end of the first week postpartum. The earlier it presents in pregnancy the more threatening it can become.

As I began my research last week I thought this post would be relatively short. Going back to my 2001 MSc lecture notes there was not a whole lot of dietary/nutrition related evidence to work with. However, as I began to search through recent medical databases I was pleased and enthralled with the emergence of new information. The definitive causes of preeclampsia are not known and there are many theories. Nutritional factors, however, do seem to be at play.

Keep body weight in check:
Maternal overweight and obesity places women at risk. A BMI (body mass index) greater than 25 is seen as a risk. To work out your BMI divide your weight in kg / by your height in metres² (height x height) or use an online BMI calculator e.g. the NHScalculator. A recent study(2) also shows that gaining a lot of weight during pregnancy maybe arisk factor. This study looked at 34,143 women age 18-34 who were already overweight at the start of their pregnancies. Gaining more than 15lb during pregnancy was a significant risk factor for the development of preeclampsia and gaining more than 25lb increased the risk further. The lowest risk of adverse outcomes was for women who gained 6-14lb.

Dietary fibre:
The study(1) mentioned in my opening paragraph was carried out because evidence already exists for the beneficial effects of fibre in reducing hypertension (high blood pressure). 1538 pregnant women were involved in the study and their dietary intake was assessed 3 months before and during early pregnancy. Women with the highest dietary fibre intake (more than 21g/day) had a significantly reduced risk of preeclampsia when compared to women with the lowest dietary fibre intake (less than 12g/day). These are important findings, as I have mentioned in previous blog posts the average intake of fibre in the UK is low (around only 12g/day). The recommended daily intake is currently set at 18g/day in the UK, however for optimal health many experts regard at least 25g/day as necessary.

This most recent study adds weight to earlier evidence(3) which also found that fibre was associated with a significantly reduced risk of preeclampsia. The researchers also found that potassium intake was a significant protective factor (I will be discussing potassium intake a blood pressure further on Thursday). This evidence was interesting as it mentioned specific foodstuffs, with fruits and vegetables being associated with a reduced risk of preeclampsia development (unsurprisingly since vegetables and fruits are great sources of fibre and potassium).

Fruits, Vegetables and Antioxidant Vitamins:
You may be sick of my constant mentioning of vegetables and fruits?! Well, they really are vitally important to health and I will be writing about them as often as possible! As indicated above these super foods provide the body with fibre and are fantastic sources of potassium. In addition to this they are packed full of vitamins, minerals and flavonoids (bioactive plant compounds). Many of these plant nutrients act as antioxidants in the body.

Antioxidants protect our cells from the damaging effects of highly reactive molecules called free radicals (which cause oxidative stress in the body). There is mounting evidence that these destructive molecules, together with lowered antioxidant defences, play a significant role in the development of preeclampsia. The body does produce its own antioxidants but also relies on vitamins, mineral and phytochemicals (including flavonoids) from the diet, especially from colourful vegetables and fruits, for additional valuable supplies.

Dietary antioxidants and supplemental vitamin C and E(4,5), lycopene(6), selenium(7,8) and multivitamins(9) all appear to have some protective role to play against the development of preeclampsia, although the evidence for supplements is not yet conclusive andfurther large trials are needed. The evidence to date certainly seems to suggest an important role for fruit and vegetable consumption during pregnancy, a variety of colourful vegetables and fruits will provide a whole array of vital nutrients to the body. Selenium is not as widely available in the UK diet, although Brazil nuts are a terrific source.

In addition to diet you may wish to discuss taking a pregnancy safe multi-vitamin and mineral supplement with your GP, midwife or health professional.

Omega 3 Essential Fatty Acids:
Recent evidence suggests that women with preeclampsia have reduced levels of essential omega 3 fatty acids in their blood(9,10). Omega 3 fatty acids are vital for the efficient functioning of the immune system. A lack, or imbalance, of these fatty acids is associated with inflammation in the body. Inflammatory chemicals (cytokines) have been implicated in the development of and risk for preeclampsia. Omega 3 fatty acids are essential for optimal foetal development (and are especially important in brain and immune development) and it is important to ensure a regular supply during pregnancy. I have spoken aboutthese fatsextensively in previous posts. Good dietary sources are oily fish (salmon, trout, mackerel, sardines) and flaxseeds or walnuts for vegetarians/vegans. Many people in the UK do not eat these foods regularly. Speaking to your GP or midwife about an omega 3 supplement, a fish oil (providing about 250mg EPA and 250mg DHA per day) or flaxseed oil may be prudent to ensure adequate levels throughout pregnancy and beyond.

At the moment the evidence is preliminary and needs backing up by large, well designed trials and further research. Personally, I feel that the take home message is that being a normal weight (BMI 19-24), being physically active and having a healthy, nourishing diet rich in fruits, vegetables and essential fats may be protective.....great advice for good health for all of us then!

(1) Qiu et al. 2008. Dietary fibre intake in early pregnancy and risk of subsequent preeclampsia. American Journal of Hypertension. 21:903-909 [EPub doi:10.1038/ajh.2008.209 17 July]
(2) Langford A et al. 2008. Does Gestational Weight Gain Affect the Risk of Adverse Maternal and Infant Outcomes in Overweight Women? Matern Child Health J. [Epub ahead of print]
(3) Frederick, I. O., et al. Dietary fiber, potassium, magnesium and calcium in relation to the risk of preeclampsia. J Reprod Med. 50(5):332-344, 2005.
(4)Chappell LC et al. 1999. Effects of antioxidants on the occurrence of preeclampsia in women at increased risk: a randomised trial. The Lancet. 354:810-816
(5)Chappell LC et al. 2002. Vitamin C and E supplementation in women at risk of preeclampsia is associated with changes in indicies of oxidative stress and placental function. Am J Obstet Gynecol. 187:777-784
(6)Sharma JB et al. 2003. Effect of lycopene on preeclampsia and intra-uterine growth retardation in primigravids. Int J Gynaecol Obstet. 81:257-262
(7)Han L & Zhou SM. 1994. Selenium supplement in the prevention of pregnancy induced hypertension. Chin Med J. 107:870-871
(8)Rayman et al. 2003. Low selenium status is associated with the occurrence of the pregnancy disease preeclampsia in women from the United Kingdom. Am J Obstet Gynecol. 189:1343-1349
(9) Bodnar LM et al. 2006. Periconceptional multivitamin use reduces the risk of preeclampsia. Am J Epidemiol. 164:470-477
(10) C et al. 2006. Erythrocyte omega-3 and omega-6 polyunsaturated fatty acids and preeclampsia risk in Peruvian women. Arch Gynecol Obstet. 274:97-103
(11)Mehendale S et al. 2008. Fatty acids, antioxidants, and oxidative stress in pre-eclampsia. Int J Gynaecol Obstet. 100:134-238

Written by Ani Kowal

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