Under normal circumstances blood pressure drops during pregnancy due to the effects of hormones on the blood vessels causing them to dilate. Problems with placental blood flow can lead to 1 in 10 pregnant women developing raised blood pressure accompanied by the appearance of protein in the urine (proteinuria) and retention of excessive amounts of fluid in the body (oedema). It is not usually seen before the sixth month of pregnancy and most women develop the condition at the end of their pregnancy. However, only 1 out of 100 women will have the severe form of the condition.
It is not known why some women develop high blood pressure during pregnancy. Certain pre-existing conditions increase the risk of developing high blood pressure. They include:
- first pregnancy
- high blood pressure before pregnancy
- chronic kidney diseases
- previous pregnancies affected by pre-eclampsia
- carrying twins or triplets.
Measuring a woman’s blood pressure is an essential part of any antenatal clinic visit. As a general rule a blood pressure greater than 140/90mmHg in pregnancy is considered to be raised. Very high blood pressure (greater than 170/110mmHg) may be accompanied by headaches and flashing lights before the eyes.
If there is weight gain with swollen hands, feet, face or other parts of the body a woman should have her blood pressure and urine checked promptly.
Diet and Lifestyle Factors
Unlike other conditions that cause high blood pressure, restricting salt or using diuretics can worsen pre-eclampsia by reducing the blood flow to the kidneys and placenta. In pre-eclampsia, unrestricted use of salt and an increased consumption of water are needed to maintain normal blood volume and circulation to the placenta.
Elevated homocysteine levels may precede pre-eclampsia. Homocysteine damages the lining of blood vessels, which can lead to the pre-eclamptic signs of elevated blood pressure, swelling, and protein in the urine.
Pre-eclampsia is a potentially serious and life threatening condition for both mother and baby. Good nutrition is essential to avoid excessive weight gain and minimise the chance of having pre-eclampsia.
In addition to eating a healthy, well balanced diet you should aim to eat generous amounts of:
Herrings – for their vitamins A, B and D iron, calcium, minerals and omega 3 fatty acids.
Apples – to reduce the risk of indigestion and for their soluble fibre content which helps avoid becoming constipated.
Broccoli – for vitamins A and C and folic acid.
Brown Rice – for B vitamins, minerals and protein
Kiwi fruit – for vitamin C, fibre, vitamin E and potassium which fights fatigue and indigestion
Onions and Garlic – for the health of the heart and circulation
Walnuts – for protein, B vitamins, minerals including calcium, zinc and iron
Eliminate all process and refined foods from your diet, particularly hydrogenated and trans-fats found in margerine, frying oils and fried foods.
Take time out to relax, join a yoga in pregnancy class and get plenty of fresh air and physical exercise such as walking or swimming.