About two to three women per thousand of reproductive age have diabetes before conception. Type I diabetes mellitus, also known as insulin-dependent diabetes mellitus (IDDM), complicates less than 0.5% of pregnancies. 1 Type II diabetes mellitus, or non-insulin dependent diabetes mellitus (NIDDM), is less common in the age group likely to become pregnant. When glucose intolerance is first identified during a pregnancy this is called gestational diabetes, which complicates approximately 5% of pregnancies. 2 Women with a history of gestational diabetes are likely to develop Type II DM. 3