Congenital Upper Limb Anomalies 177calcium have been associated with gestational hypertensive disorders, which
can increase the risk of birth defects (Li et al., 2011), although a causal
relationship for the former has not been found (Maine, 2000). Some
associations have been well-established, such as a maternal deficiency of folic
acid and thiamine to neural tube defects in the fetus and neonatal death
(Ladipo, 2000). The effects of micronutrient deficiency (including copper, zinc
and manganese) are less clear in humans than in animals. Manganese
deficiency in cattle, however, has been reported to include impaired growth,
impaired reproductive function and overt congenital limb anomalies (de
Carvalho et al., 2010; Allen and Dart, 2015).
Diabetes Mellitus
A correlation has been reported between elevated hemoglobin A1c
(HbA1c) levels and the incidence of major congenital anomalies in infants of
diabetic mothers (Miller et al., 1981). HbA1c levels during pregnancy that
exceed 11.5% are associated with congenital abnormalities in 66% of the
offspring, but levels below 9.5% are not associated with increased frequency
of anomalies in infants of diabetic mothers (Nielsen et al., 1997). Defects of
the heart, central nervous system (CNS), kidneys, and skeleton predominate,
however, other anomalies including those observed in the VACTERL
association have also been reported. (Gilbert-Barness, 2010).
Researchers from the National Birth Defects Prevention Studies (NBDPS)
found that pre-existing diabetes was more common among mothers of babies
born with a range of birth defects when compared to mothers with gestational
diabetes. The birth defects include anencephaly, hydrocephaly, cleft lip (with
or without cleft palate), absent kidney, limb deficiencies, and a variety of heart
defects. Additionally, if the mother was overweight or obese and had
pregestational diabetes, the risk of these birth defects was increased. (Correa et
al., 2008)
Infections
Cytomegalovirus (CMV)
The most common viral infection of the fetus is congenital CMV
infection, which can lead to spontaneous termination of pregnancy when the
embryo is infected during the first trimester. Exposure later in the pregnancy