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High blood pressure during pregnancy

High blood pressure during pregnancy is always of some concern. However, a woman’s blood pressure can fluctuate for many reasons and the occasional high reading does not always indicate there is a problem. The following is a brief overview of high blood pressure readings as well as an explanation of pre-eclampsia(the type of high blood pressure that is usually associated with health concerns during pregnancy). If you would like to have a better understanding of how the blood pressure is measured, why it usually increases and decreases during pregnancy and what this may indicate, you can read tests during pregnancy - blood pressure. For more in depth information on the health effects of pre-eclampsia and how this condition may be treated you can read blood pressure, pregnancy and pre-eclampsia.

It is estimated that about 10% of pregnant women will have their blood pressure recorded as being ‘above normal’ at some point before they give birth. However, this is regarded as being quite normal, because a ‘one off’ high reading does not really indicate a health problem. It is only after multiple blood pressure readings taken at separate visits (or over a few hours) that it is possible to make a diagnosis of high blood pressure during pregnancy, or ‘pre-eclampsia’

 To diagnose pre-eclampsia there also needs to be other physical signs. The main sign is protein in the urine (detected through an instant urine test) and sometimes swelling or fluid retention (although this can be a normal occurence for many women during pregnancy). If there is no protein in the urine, then it is likely that the woman is just feeling anxious or stressed, or is doing too much in her general day to day life. If this is the case, her blood pressure will usually settle down after some rest and reducing her workload and commitments. If your caregiver is concerned, they may take your blood pressure again during your pregnancy visit, or ask you to return within a few days (or go to your local doctor) to have it re-checked. Often the second reading shows that the blood pressure has lowered. Be aware that there are no health risks for you or your baby if your blood pressure is a little high on the odd occasion.

It is also common for a woman’s blood pressure to be a little higher at her first pregnancy visit, often referred to as ‘white coat syndrome’ because it is due to the stress of seeing a health care professional for the first time. It may also be a little higher when you arrive at the hospital during labour or if you have had a lengthy wait to be seen for your pregnancy check up, or after receiving some concerning news. Again, the blood pressure should settle down to a lower level within a short time period after you emotionally adjust.

Some women develop what is called ‘gestational hypertension’. This is a slightly raised blood pressure that is first noticed after 20 weeks of the pregnancy that often continues for up to 3 months after the birth. The blood pressure is at a higher level than expected, but not enough to require medications or to affect the woman’s health (like ‘pre-eclampsia’). Women with gestational hypertension and their babies are normally quite well and are not generally affected. If you have gestational hypertension, you may be monitored a little more closely to make sure it doesn’t develop into pre-eclampsia.
Pre-eclampsia
Pre-eclampsia (’PE’) or Pregnancy induced hypertension (’PIH’), are the medical terms given to high blood pressure during pregnancy that may cause health concerns for the woman and her baby. For the woman, pre-eclampsia may affect the normal functioning of her kidneys, liver, brain and blood clotting system. For the baby, it may affect the functioning of the placenta.

Pre-eclampsia usually only occurs after about 20 weeks of the pregnancy and can affect between 2 - 8% of pregnant women. The precise cause of pre-eclampsia is still not clear, but it is thought that it may be due to an imperfect implantation of the placenta early on in the pregnancy. The theory is that less blood vessels from the placenta are able to access the woman’s blood supply, and as the pregnancy progresses there is a slight decrease in blood flow through the placenta. In response to this the placenta is thought to release certain chemical substances into the woman’s bloodstream causing pre-eclampsia.

However, it has also been noted that pre-eclampsia tends to be more common in women having their first baby and women having another baby with a new partner. It is also more common for teenage mothers and women over 35 years , when compared with women between these age groups. Women with a family history of pre-eclampsia (your mother or another close female relative having pre-eclampsia during their pregnancies), women with diabetes and women having twins or triplets (or more) are also more likely to develop pre-eclampsia.

Up to 50% of women who have had pre-eclampsia with a previous pregnancy will develop pre-eclampsia again during a subsequent pregnancy, but it is usually in a milder form. Women who have developed pre-eclampsia during a pregnancy, may also be at an increased risk of developing high blood pressure later in life.