Pregnancy takes over a woman's body and the effect can be seen all around an otherwise seemingly healthy body. Once you start growing another life inside of you all your weaknesses will show up. Hypoglycemia (low blood sugar), is often a symptom of inadequate energy (calorie). This could be due to simply not eating enough to support the activity going on inside of you, a lack of good quality food (i.e not enough nutrition quality despite quantity being high enough) or even quality being too good (i.e your weakened system can't digest all the natural whole foods you want to eat).
Hypoglycemia's characteristic dizziness, lightheadedness, shakiness or fatigue may be as a result of the hormonal changes that accompany pregnancy. These can also interfere with the way your body uses insulin, another hormone. When your blood sugar drops, you're likely to feel dizzy or light-headed.
As you become so lightheaded or dizzy the amount of oxygen you receive (thats why you feel dizzy and faint) and that supplied to your baby can decrease, increasing the risk to your baby. Hypoglycemia also increases your risk of developing a serious pregnancy complication called preeclampsia, or severe high blood pressure, according to a 2005 study published in the "Journal of Perinatology"
Hypoglycemia requires dietary changes, increasing the number of calories you eat and having a small meal or snack about every two hours will typically resolve your symptoms. However, I'm not a GP so I must advise you to work closely with your care provider or family doctor.