The important physiological role of docosahexaenoic acid (DHA) in fetal and infant development has attracted widespread attention in the nutrition community. Pregnant women and lactating mothers are the main providers of fetal and infant nutrition, and their DHA nutritional status has an important impact on the nutrition and development of fetal and infant DHA. Infants who are supplemented with DHA during pregnancy and/or lactation have higher blood DHA levels and better physical, visual and intellectual developmental levels. In this paper, recent research data on maternal DHA intake and fetal and infant DHA nutritional status and developmental relationships were reviewed.
Essential fatty acids (EFA) include linoleic acid (LA) and linolenic acid (LNA), and their relationship to infant nutrition has been recognized. Docosahexaenoic acid (DHA) is a derivative of linolenic acid in the body and is a type of n-3 long-chain polyunsaturated fatty acid (LCPUFA). It is essential for the development of fetal, infant brain, retina and other tissues. substance. Most of the DHA required for fetal and infant growth and development should be run from the mother. The nutritional status of the mother DHA directly affects the nutritional status of the fetal DHA, which in turn affects fetal development, especially brain development. In recent years, the nutritional status of newborn DHA and its impact on brain development has attracted the attention of the nutrition community.
Most studies have reported positive effects of maternal DHA nutritional status on fetal, infant physical, visual and intellectual development, but there are also inconsistent findings.
Physical development
Physical development is a sensitive indicator of whether a baby is adequately nourished. Increasing dietary DHA intake in pregnant women can affect the length, head circumference and weight of the fetus. The lack of DHA in the mother's diet is often associated with low placental weight and neonatal low head circumference and low birth weight. Maternal blood arachidonic acid (AA) concentration was positively correlated with fetal birth weight. Another study found that when seafood intake was between 0 times/weeks and 3 times/week, the frequency of intake was positively correlated with neonatal weight and length. In a randomized trial of DHA supplementation at the end of pregnancy, Smuts et al. found that newborns' birth weight, length and head circumference also increased with the increase in DHA intake during the second trimester. The concentration of DHA in breast milk is positively correlated with the weight gain of the first 3 months of the baby, and the DHA level of cord blood reflecting the long-term DHA status of the fetus is positively correlated with the head circumference, body weight and body length of the newborn. However, some studies have not found that DHA intake is related to infant growth rate 30 weeks before pregnancy, which may be related to DHA mainly concentrated in the fetal brain within 3 weeks of the end of pregnancy, and the end of pregnancy is the peak period of fetal brain development. There are also studies that do not support the promotion of DHA on infant growth and development. The possible reason is that DHA content in cord blood is not only affected by maternal blood DHA level, but also closely related to placental transport function. EFA transport from maternal to fetus may be neonatal EFA. Limitations of condition and growth.
Vision development
The current conclusions about the effects of maternal supplementation with DHA on infant visual development are not completely consistent.
DHA is essential for the normal development of vision and nervous system in infants, especially 4-8 months. Early DHA status in the fetus affects future vision development. Dietary supplementation of fish oil in pregnant women can increase DHA levels in neonatal red blood cells, while neonatal red blood cell DHA levels are positively correlated with visual function. From this perspective, maternal supplementation with DHA has a positive impact on infant vision development. If a study finds that pregnant women who eat more fatty fish have good vision, these children can focus on subtle images at the age of three and a half, and can judge the surrounding objects like adults. In recent years, studies have shown that the visual acuity of infants fed with normal formula is immature, which is lower than that of breast-fed groups. Breast-fed infants have even better visual acuity than DHA-fed, which contains DHA in breast milk and lacks formula. Related to DHA. Direct supplementation of DHA to infant formula also has a positive effect on infant vision development. Intervention trials have shown that DHA supplementation groups have similar erythrocyte phospholipid composition and infant visual acuity to infants in the breastfeeding group when the diet is supplemented with appropriate DHA. Full-term children do show consistently relatively good visual function; although DHA is only supplemented during the first 17 weeks of life, its effect on vision persists at 52 weeks, suggesting a critical period in early visual development. Dietary supplementation with DHA can cause persistent changes in the underlying visual structure and/or function. A slight difference in visual function can clarify the importance of DHA needs at critical stages of vision development. However, some studies have not found a positive effect of maternal supplementation with DHA on infants' visual acuity. The researchers found that supplementation of DHA in pregnant women does not promote the maturation of visual prosthetic potential (VEP) in healthy full-term infants, but the DHA status at birth is related to the development of trans VEP in the early postnatal period, suggesting that the infant's own DHA status can affect vision. The maturity of the central conduction.
Intellectual development
At 18 months after birth, DHA is considered to be the most likely and most important component of breast milk to significantly improve infant intelligence. The ratio of breast milk AA to DHA is similar to the ratio of the two in the baby's brain, and is positively correlated with the growth rate of the anterior occipital head circumference and the weight gain of the brain in January and March. Within 40 weeks of birth, DHA in the cerebral cortex of breast-fed infants continued to accumulate, whereas in the cerebral cortex of infants fed with no DHA, the proportion of DHA accumulation was only maintained at the time of birth. The concentration of DHA in the brain of breast-fed infants, the motor development index (PDI) and mental development index (MDI) representing the level of intelligent development were significantly higher than those of mixed-fed and artificial-fed infants, and even higher than those supplemented with DHA. Further studies confirmed that DHA levels in mature milk, term maternal blood and cord blood were positively correlated with PDI and MDI. Xiang et al. supplemented 590 pregnant women with n-3 and n-6 LCPUFAs. The results showed that neonates with high DHA concentrations in cord blood erythrocyte phospholipids had higher brain maturity. Helland et al found that the intelligence score of 4-year-old children was significantly correlated with their mother's DHA intake during pregnancy. This indicates that the high DHA content in the milk is beneficial to the needs of the baby during the rapid development of brain growth after birth. When the mother is supplemented with DHA, this benefit is more obvious by increasing the DHA content in the mother's blood and milk. Although many studies have confirmed the important influence of maternal DHA on infants' mental development, the optimal level of DHA in maternal blood and breast milk is still required for a fetus and infant to achieve the best neurological maturity and maximum neurological benefits. Not sure.
In view of the methodological limitations of infant visual acuity and mental development assessment, there is currently no firm conclusion about the long-term and functional effects of maternal DHA nutritional status on infant vision and mental development. Inconsistent conclusions and human and animal studies The results all indicate the complexity of early nutrition and behavioral interventions. There is little positive conclusion about the functional necessity of a single dietary factor in the development of the central nervous system. Even in articles that reported that dietary DHA has an impact on visual development, the impact is generally small. Moreover, these conclusions are based on the influence of methodologies and measurement indicators that are not yet fully perfected, or whether there are actual differences, and further research and discussion is needed. In summary, most studies support the mother's DHA intake has a positive impact on fetal and neonatal DHA nutrition and development, therefore, it is of great significance to improve the dietary DHA intake of mothers during pregnancy and lactation.