It is perfectly normal for the blood pressure to show a little variation in pregnancy. This happens because of the pregnancy hormone called as progesterone. Progesterone relaxes the wall of the blood vessels, and cause a drop in the blood pressure. So we normally notice a drop in blood pressure as 100/60 or 90/60 in the first and second trimesters and it reaches its lowest in the mid trimester. After 24 weeks of pregnancy, it slowly starts to rise and is much so that towards the end of the pregnancy it reaches its pre pregnancy values.
