Fetal growth, reduced

The fetoplacental unit includes maternal and fetal placental circulations, other placental functions, umbilical cord and amniotic fluid. If chemicals — for example, vasoactive drugs — reduce the placental circulation or cause umbilical vasoconstriction, then marked prolonged action may cause fetal death from anoxia, but an action for less than 2 h in rodents may cause fetal growth retardation or... 

Generally, vitamin A serves three classes of functions (1) support of the differentiation of epithelial cells, (2) support of the viability of the reproductive system (fetal growth and vitality of the testes), and (3) utilization in the visual cycle. Dietary retinoic acid can support only the first function. Animals raised on diets containing retinoic acid as the only source of vitamin lose their ability to see in dim light and become sterile. In males, sperm production ceases. In females, fetuses are resorbed. Retinoic acid cannot be stored in the liver, as it lacks the hydroxyl group needed for attachment of the fatty acid. Retinyl esters, retinol, and retinal are interconvertible. Retinal can be oxidized to form retinoic acid. All three functions of vitamin A can be supported by dietary retinyl esters, retinol, or retinal. Although these forms can be converted to retinoic acid, retinoic acid apparently cannot be reduced to form retinal. These relationships are summarized in Figure 9.44. 

The developmental toxicity of zinc in experimental animals has been evaluated in a number of investigations. Exposure to high levels of zinc in the diet prior to and/or during gestation has been associated with increased fetal resorptions, reduced fetal weights, altered tissue concentrations of fetal iron and copper, and reduced growth in the offspring. 

Embolization may lead to a reduced uterine blood flow during gestation and it is well known that uterine blood flow is crucial for fetal growth and survival [8, 48]. A bilateral uterine artery embolization blocks the main arterial supply to the embryo and it has been demonstrated that the reduction in uteroplacental blood flow using ligation [5], clamp [4], occlusion [13] or embolization [45] significantly affects fetal and placental weight. 

Adverse developmental effects were found in infants and children at maternal BLLs imder 10 pg/dL, and reduced fetal growth and low birth weight... 

Hg/dL and over are associated with adverse effects on sperm or semen and that BLLs of 20 pg/dL and over are associated with delayed conception time. Decreases in sperm count, density, and concentration were seen in men who had mean BLLs of 15-68 pg/dL. The NTP also concluded that there was sufficient evidence that maternal BLLs under 5 pg/dL are associated with reduced fetal growth or lower birth weight. There is limited evidence that maternal BLLs under 10 pg/dL are associated with preterm birth and spontaneous abortion. Prospective studies reviewed by the NTP provided limited evidence that prenatal exposure to BLLs under 10 pg/dL is associated with reduced postnatal growth in children. The NTP recognized that its conclusions about prenatal lead exposure were confounded by possible continuing postnatal exposure to lead (associated with BLLs under 10 pg/dL) that is also associated with reduced postnatal growth in children. 

Although the results are not entirely consistent among studies, the evidence on maternal or umbilical cord blood lead (under 10 gg/dL) and the large number of studies led the NTP to conclude that there was sufficient evidence of an association between maternal BLL under 10 gg/dL and reduced fetal growth and low birth weight. In contrast, the NTP concluded that there was only limited evidence that maternal BLL under 10 gg/dL is associated with spontaneous abortion and preterm birth. Although a number of prospective and cross-sectional studies have reported an association between prenatal BLL under 10 gg/dL and preterm birth, the conclusion of limited evidence was based primarily on inconsistency of the data and a large study of mother-infant pairs that failed to find the same relationship. EPA (2012) also concluded that there was little evidence to support an association between maternal or paternal lead exposure and the incidence of spontaneous abortion. 

The committee concludes that the evidence is snfficient to infer causal relationships between BLLs over 40 pg/dL and adverse effects on sperm and semen, inclnding decreased sperm count, reduced sperm motility, and increased morphologic abnormalities (see Table 4-4). The committee concludes that the evidence to infer causal relationships between BLLs under 40 pg/dL and adverse effects on sperm and semen is limited. The committee also found strong evidence of a causal relationship between prenatal maternal BLLs under 10 pg/dL and adverse developmental effects in infants and children and sufficient evidence of an association between maternal BLLs under 5 pg/dL and reduced fetal growth and low birth weight (see Table 4-5). The committee s conclusions are consistent with those of EPA and the NTP. 

Washino N, Saijo Y, Sasaki S, Kato S, Ban S, Konishi K, Ito R, Nakata A, Iwasaki Y, Saito K, Nakazawa H, Kishi R (2009) Correlations between prenatal exposure to perfluorinated chemicals and reduced fetal growth. Environ Health Perspect 117 660-667... 

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