High blood before pregnancy
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.
High blood pressure before pregnancy
A few women will have high blood pressure before their pregnancy. This is known as 'essential hypertension'. You may already be aware that your blood pressure is higher than normal or it may be something that has been detected at a preconceptual health check (or at the first pregnancy visit, before 20 weeks).
Essential hypertension detected during pregnancy shows the blood pressure being unexpectantly higher but no fluid swelling (called 'oedema') and no protein detected in the urine (which happens with high blood pressure associated with being pregnant, or 'pre-eclampsia'). Essential hypertension is more common in older women, women who smoke and/or women with a family history of high blood pressure and sometimes if you had high blood pressure with a previous pregnancy.
Other medical conditions that may cause high blood pressure before (or during early) pregnancy are kidney disease, heart disorders, or very rarely a molar pregnancy. If your high blood high blood pressure is caused by another health condition it is referred to as 'secondary hypertension'. Women who were previously unaware of their high blood pressure will usually have additional blood tests to rule out other possible health conditions.
Once a woman with essential hypertension conceives, her caregiver will aim to control the blood pressure at (or below) 140/90 throughout the pregnancy. In some cases, this may mean starting medications to lower the blood pressure (called 'antihypertensives'), or adjusting or changing the dosages if you already take medications. If you see your doctor before you conceive, adjustments to medications may be made in preparation for a pregnancy.
During pregnancy, it is ideal for you to see a physician who specialises in high blood pressure as well as an obstetrician (these can be through either the public system or privately). These doctors will usually work in partnership, with the physician dealing mainly with treating the blood pressure and the obstetrician managing the overall pregnancy and birth care. You will probably need to continue seeing the physician for weeks (or months) after the birth if your blood pressure is not well controlled.
Women with uncomplicated, controlled essential hypertension tend to have similar health outcomes to women with a normal blood pressure (as do their babies). The only concerns tend to be that women with essential hypertension are about 5 times more likely to develop pre-eclampsia, than women who start the pregnancy with a normal blood pressure. A few babies may also be at increased risk of poor growth during pregnancy due to 'placental insufficiency' (also known as a baby that issmall for gestational age).
Last revised: Thursday, 15 May 2014
This article contains general information only and is not intended to replace advice from a qualified health professional.