Congenital anomalies in diabetic pregnancy

What it is

Diabetes in pregnancy carries its own set of fetal congenital anomalies, and the timing matters. In the first trimester the fetal risk is birth defects and spontaneous abortion; macrosomia and hyperglycemia belong to the second and third trimesters. Overt diabetes in pregnancy is pregestational DM diagnosed for the first time during pregnancy, usually in the first trimester, by RBG at or above 11.1 mmol/l, or FBS at or above 7 mmol/L, or HbA1c at or above 6.5%; its complications are abortions and congenital anomalies.

Causes and risk

The anomalies follow glycemic control. The desirable HbA1c value in pregnancy is under 6.5%, and in a woman who is not a known diabetic the target is under 6%. A high HbA1c in the first trimester puts her at risk of miscarriage, through hyperglycemia and uteroplacental insufficiency, and raises the risk of UTI and candida infection, and of ketoacidosis in type 1.

How it presents

The anomalies named are these:

• Cardiac defects, the most common and the most important to mention: VSD first, then ASD. Transposition of the great arteries is also listed, and fetal complications of chronic DM are given as cardiovascular anomalies.
• Neural tube defects: spina bifida and anencephaly.
• Renal anomalies.
• Caudal regression syndrome, which is very specific for maternal diabetes.

An anomaly scan showing an abnormality in a woman with GDM is the setting in which these are found.

The size of it is a 6% risk of congenital malformations, a three-fold increase compared with the non-diabetic population, and the range of anomalies is similar to that for the general population; named with it are cardiac malformations, sacral agenesis (caudal regression syndrome) and hypoplastic left colon. Set out by system, the list runs: neurologic, anencephaly, microcephaly, holoprosencephaly and neural tube defects; cardiovascular, transposition of the great vessels with or without ventricular septal defect, coarctation of the aorta, atrial septal defect, single ventricle, hypoplastic left ventricle, pulmonic stenosis, pulmonary valve atresia, double outlet right ventricle and truncus arteriosus; gastrointestinal, duodenal atresia, imperforate anus, anorectal atresia, small left colon syndrome and situs inversus; genitourinary, ureteral duplication, renal agenesis and hydronephrosis; skeletal, caudal regression syndrome and hemivertebrae; and a single umbilical artery. Alongside the malformations there is a three-fold increase in growth restriction in mothers with long-standing microvascular disease.