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.