During pregnancy, blood vessels dilate causing blood pressure to drop. This can cause dizziness or lightheadedness, notes Mayo Clinic. This is not an unusual occurrence in the first trimester of pregnancy, but if the dizziness becomes severe or is accompanied by bleeding, seek medical attention from a qualified health professional.
BabyCenter explains that the cardiovascular system undergoes many major changes during pregnancy. Symptoms such as dizziness and nausea are common reactions to the swings in blood pressure and heart rate of pregnant women. The heart has to work harder to pump more blood into the body, as a larger supply is necessary to help support the growth of the baby. Blood pressure reaches its lowest point by mid-pregnancy, and then starts to go back up until it reaches normal levels by the end of the pregnancy.
The dizziness may be inevitable for short periods of time, but BabyCenter explains that avoiding certain situations helps to keep the dizzy spells to a minimum. The site recommends that pregnant women avoid lying on their backs, taking hot baths or exercising too strenuously, as doing these activities only makes the dizziness worse. Staying well-hydrated, taking prenatal vitamins and standing up slowly can help to avoid feelings of lightheadedness.