Why gestational diabetes doesn't cause as major congenital anomalies as Diabetes Mellitus During Pregnancy?

diabete gestationnel c est un troble de la regulation glycemique cad  du taux de sucre ou plutot de glucose dans le sang durant la grossesse....

il peux causer juste l exces de poids foetal macrosomie....

Given that abnormalities in carbohydrate metabolism do not usually appear to the III trimester of pregnancy, patients with gestational diabetes is not at risk of developing congenital anomalies of the fetus, as in pregestatsionnom diabetes. Complications for infants of mothers with gestational diabetes include macrosomia, shoulder dystocia, and hypoglycemia in the early neonatal period, long-term consequences: obesity, susceptibility to type 2 diabetes, as well as intelligent motor disorders. 

fetal organs develop in the first part of pregnancy, while gest Diab develops after 20 wks gestation, after fetal organs have fully developed.It is usually not severe. Also it does not have the complications of the long standing DM. DM can cause cong anomalies mainly cardiovascular and neural tube defect.

The risk for congenital anomalies is very high during embryogenesis which occur during first trimester, while gestational diabetes usually starts in third trimester of pregnancy when hormones from the placenta block insulin.

fetal organs develop in the first part of pregnancy,after fetal organs have fully developed. Also it does not have the complications of the long standing DM. 

gestational diabetes only occure during pregnancy , when mother has high blood sugar level, with out any previous history. And it settled down after delivery mostly. But in mellitus , mother already have diabetes and symptoms becomes more intense during pregnancy which can affect fetus as well.

GESTATIONAL DIABETES IS SEEN AFTER EMBROYONIC PERIOD OF THE FOETUS BUT DIABETIS MELLITUS IS PRESENT IN THE MOTHER BEFORE CONCIEVING SO  CONGENITAL ABNORMALITIS IS SEEN IN THE BABY.

Because GDM appear after completion of organogenesis, unlike the established DM pre-dating pregnancy which if uncontrolled will affect the developing embryo especially if the DM was not uncontrolled as indicated with high HbA1C.

In gestational diabetes hyperglycemia occurs for the first time in the late second trimester after the organogenesis, where as in diabetes mellitus poor control of diabetes in the first trimester during organogenesis is associated with congenital anamolies. 

1. AGE: advanced glycation end products are low in GDM in contrast to DM complicating pregnancy. 

2. Warkany hypothesis: In T1, as the organogenesis are complete, congenital malformation are more common with DM complicating pregnancy in contrast to GDM

gestational diabetes occur at 3rd trimester , and anomalies can be just in the 1st trimester