Definition: Maternal diabetes mellitus is considered to be a very significant risk factor in pregnancy and is responsible for a high rate of perinatal mortality (4%). It is important to differentiate pre-existing diabetes mellitus from gestational diabetes. In the pre-existing form, in addition to fetal macrosomia and immaturity of organs, there is an increased incidence of fetal malformations, especially if glycemic control has not been optimal during the pre-conception and early first-trimester stages.

Incidence: Gestational diabetes is seen in up to 3% of pregnancies.

Associated symptoms: These may include macrosomia and hydramnios (late second trimester), and—when there is maternal vascular damage—growth restriction (Doppler ultrasonography of the uterine vessels at 22 weeks).

Associated malformations: Anencephaly, holoprosencephaly, neural tube defects (2%), microcephaly. Caudal regression syndrome, cardiac anomalies (2–4%) such as transposition of great vessels, VSD, tetralogy of Fallot. Bowel atresia, renal anomalies such as renal hypoplasia or hydronephrosis.

Differential diagnosis: Syndromes associated with macrosomia: Beckwith–Wiedemann syndrome, Marshall–Smith syndrome, Sotos syndrome, Weaver syndrome.

Clinical management: Oral glucose tolerance test, profile of blood glucose levels for 1 day, tight glycemic control (fasting values below 100mg%, peak values not exceeding 130 mg%). If dietetic measures are insufficient, therapy with insulin is required. Serial Doppler assessments.