Congenital anomalies

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An association between maternal diabetes mellitus and congenital malformations has been suspected since the nineteenth century.21,22 Despite the considerable advances in the management of the pregnancy complicated by diabetes, the rate of congenital malformations has not changed dramatically. Congenital malformations and their sequelae have replaced intrauterine fetal death and respiratory distress syndrome as the major causes of morbidity and mortality in infants of diabetic mothers.21 Their estimated frequency is 6-10%, or 3- to 5-fold higher than the rate in the general population.23 Therefore, perinatal death as a result of congenital malformations account for approximately 40-50% in infants of diabetic mothers.24,25 Most researchers believe that high rates of severe malformations are the consequence of poorly controlled diabetes, both periconceptionally as well as early in pregnancy,26,27 though others have failed to totally corroborate these findings.28-30 The precise mechanism underlying the abnormal development of fetuses of hyperglycemic mothers has not been completely elucidated. The pathogenesis may also involve factors other than hyperglycemia, such as free oxygen radical scavenging enzymes.31 Diabetes in pregnancy is not associated with a specific fetal phenotype or syndrome, but rather affects multiple organ systems.32

The sonographic detection of recognizable congenital anomalies is an important aspect of the management of diabetic pregnancy. Diabetes-associated malformations occur very early in pregnancy, usually before the eighth week of gestation. Therefore, the evaluation should be done in the first trimester of pregnancy and repeated in the second. Cardiovascular anomalies are the most common, especially conotruncal and ventricular septal defects.33-35 Indeed, maternal diabetes mellitus has been accepted as one of the indications for fetal echocardiography because congenital heart disease occurs four to five times more frequently in the offspring of women with diabetes than in the general population.36-38 Antenatal identification is important because some defects are ductal-dependent and require immediate therapy after birth.39 Fetuses of diabetic mothers are at risk for accelerated myocar-dial growth. The cardiomyopathy is mainly related to poor glycemic control. In adequately controlled glycemia, cardiac growth and ventricular diastolic filling are normal.40,41 Second in frequency are neural tube defects (NTD). Maternal serum alpha-feto-protein (MSAFP) testing is an important indicator of NTD: second-trimester values in women with pre-gestational diabetes are on average 20% lower than in the general population. In these cases, MSAFP levels are corrected without regard to diabetic control. The sensitivity of ultrasound for the detection of NTDs associated with increased MSAFP values is reporting as high as 94%.42 Be that as it may, all diabetic pregnancies should be sonographically evaluated for NTDs regardless of MSAFP level. Anencephaly is the most common anomaly affecting the central nervous system, with an incidence of 0.57% in fetuses of diabetic pregnancy, or 3-fold higher than in the normal population (0.19%).43 Maternal diabetes is also thought to increase the risk of holoprosencephaly, which results from failure of cleavage of the prosencephalon. Interestingly, the lesion most associated with diabetic embry-opathy, namely caudal regression syndrome (caudal dysplasia sequence)44 is actually less common than cardiovascular malformations. However, it is difficult to estimate its incidence because it is often reported together with cases of sirenomelia. The pathogenesis is currently thought to be heterogenous. The primary defect is in the midposterior axis mesoderm. All degrees of severity may occur, depending primarily on the relative length and width of the early caudal deficit.35

The most severe form is presumably the consequence of a wedge-shaped early deficit of the caudal blastema.45 Associated anomalies, in accordance with the severity of the syndrome, may include imperforate anus, absence of external genitalia, renal agenesis, absence of internal genitalia except gonads, a single umbilical artery, absence of bladder, and fusion of the lower limbs. The principal findings of caudal regression syndrome on sonographic radiology are as follows: various types of lower limb anomalies ranging from hip dislocation to frog-leg deformity and equinovarus, hydrocephalus, and Dandy-Walker malformation, complete absence of the spine below L:, partial or complete absence of the caudal part of the sacrum, intraspinal anomalies in the form of meningomyelocele and sacral lipoma, whereas the pelvis is small owing to the absence of a sacrum, and the iliac bones touch or even fuse.46 Up to 16% of these cases are associated with diabetes mellitus.47,48 Although the disorder occurs 200 times more often in infants of diabetic mothers, only 1.3 per 1000 diabetic pregnancies are affected. This anomaly cannot be considered pathognomonic for diabetes since it occurs in other conditions as well. The skeletal, genitourinary, and gastrointestinal systems may also be affected. Defects involving the genitourinary system that show preponderance in infants of diabetic mothers include ureteral duplication, renal agenesis, and hydronephrosis.

Controversy exist as to the optimum time to perform the first ultrasound examination and how many subsequent examinations are needed for identification of fetal malformations.49 Fetal evaluation cannot be wholly completed during the first anatomical scan. An early scan at 10-14 weeks of gestation permits exclusion of major malformations, and an additional scan at 20-22 weeks is advisable in order to rule previously unrecognized malformations.

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  • jali holmen
    Which congenital anomaly is pathogonomic for maternal DM?
    2 years ago

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