Hello madam, Frequent low blood
sugar is common complaint in patients taking insulin. Some times it is life threatening too. But can be avoided by taking simple measures like, not skipping any meals after you take insulin (most important), reducing the dose of insulin you needed (pregnancy alters the immunity which may improve or worsen your underlying condition thus altering dose of insulin is necessary) that your doctor have done, and your growing fetus use up your glucose, so you need to eat relatively more or have to reduce your insulin dose less. it happens more in night because you are in relative fasting state whole night for almost 12hr.
Nothing to worry, needing less insulin dose is actually good. talk to your doctor he will titrate the dose for you.