Prenatal nutrition addresses nutrient recommendations before and during pregnancy. Nutrition and weight management before and during pregnancy has a profound effect on the development of infants. This is a rather critical time for healthy development since infants rely heavily on maternal stores and nutrients for optimal growth and health outcome later in life.
Prenatal nutrition has a strong influence on birth weight and further development of the infant. A study at the National Institution of Health found that babies born from an obese mother have a higher probability to fail tests of fine motor skills which is the movement of small muscles such as the hands and fingers.
A common saying that a woman "is eating for two" while pregnant implies that a mother should consume twice as much during pregnancy, but is misleading. Although maternal consumption will directly affect both herself and the growing fetus, overeating excessively will compromise the baby's health as the infant will have to work extra hard to become healthy in the future. Compared with the infant, the mother possesses the least biological risk. Therefore, excessive calories, rather than going to the infant, often get stored as fat in the mother. On the other hand, insufficient consumption will result in lower birth weight.
Maintaining a healthy weight during gestation lowers adverse risks on infants such as birth defects, as well as chronic conditions in adulthood such as obesity, diabetes, and cardiovascular disease (CVD). Ideally, the rate of weight gain should be monitored during pregnancy to support the most ideal infant development.
Background
Barker's Hypothesis: the impact of in utero conditions on fetal growth and development
The "Barker Hypothesis", or Thrifty phenotype, states that conditions during pregnancy will have long-term effects on adult health. Associated risk of lifelong diseases includes cardiovascular disease, type-2 diabetes, obesity, and hypertension. Babies born lighter in weight appear to have an increased rate of mortality than babies born at a heavier weight. This does not mean that heavy babies are less of a concern. Death rate would rise as birth weight increases beyond normal birth weight range. Therefore, it is important to maintain a healthy gestational weight gain throughout pregnancy for achieving the optimal infant birth weight.
When this theory was first proposed, it was not well accepted and was met with much skepticism. The main criticism was that confounding variables—nutrition in early life, the rate of weight gain throughout childhood, and other environmental factors—could attribute to many of the chronic diseases first noted in these low birth-weight populations. Because of this, there was a lack of support for birth weight being recognized as an independent risk factor. Subsequent research studies aimed to adjust for these environmental factors and in turn, provided more convincing results with minimal confounding variables.
"Barker's Hypothesis" is also known as "Fetal Programming Hypothesis". The word "programming" illustrates the idea that during critical periods in early fetal development, there are persisting changes in the body structure and function that are caused by environmental stimuli. This relates to the concept of developmental plasticity, which posits that genes are expressed in different ranges of physiological or morphological states as a response to the environmental conditions experienced during fetal development. Programming may be impacted by the mother's diet, and the implications of these changes can persist throughout a child's life.
Animal studies show that inadequate maternal nutrition can negatively impact the expression of various genes, the development of tissues and organs, and can be linked to permanent hypertension in offspring. Maternal nutrition extends beyond caloric intake. It encompasses a wide range of elements, like the balance of macronutrients including proteins, carbohydrates, and fatty acids, each having a unique effect on fetal growth. Deficiencies in a mother's diet can send signals to the fetus suggesting that its long-term living conditions will be those of poverty. Consequently, the baby adapts by changing its body size and metabolism to prepare for harsh conditions of food shortages after birth. Physiological and metabolic processes in the body undergo permanent changes as a result of restricted growth. When the living conditions switch from malnutrition to those of abundance, the baby is forced into an environment that works against what its body was designed for. This juxtaposition increases the baby's risk of developing diseases later in adulthood. By the same token, if the fetus growing in the womb of a healthy mother is exposed to prolonged famine after birth, the infant would be less adaptive to the harsh environment than low-birth-weight babies. Additionally, micronutrient deficiencies during pregnancy may influence the long-term outcomes related to survival and cognitive development in offspring. Although these associations are not yet fully established, they underscore the importance of adequate prenatal nutrition during this critical period.
The importance of maternal environment as it relates to fetal development has been debated. Studies show that half siblings who share a mother have more similar birth weights than those sharing a father. Other research builds on this, suggesting that over 50% of discrepancies in fetal weight can be attributed to the intrauterine environment, with the second largest contributor being the mother's genes. This research lends support to Barker's hypothesis and highlights the significance of maternal health; however, the mechanisms by which these factors (e.g., malnourishment) influence fetal weight are still under investigation.
Pedersen's Hypothesis – influences of maternal glucose concentration on fetal growth In 1952, the Danish physician Jørgen Pedersen of the University of Copenhagen, formulated the hypothesis that maternal hyperglycemia during pregnancy might cause fetal hyperglycemia, thus exposing the fetus to elevated insulin levels. This would result in an increased risk of fetal macrosomia and neonatal hypoglycemia.Erhöhte Blutzuckerwerte bei Schwangeren gefährden das Kind
The blood glucose concentration in humans is mainly dependent on diet, especially energy-ingestion and the percentage of carbohydrates in the diet. High glucose concentrations in the blood of pregnant women cause an intensified transfer of nutrient to the fetus, increasing fetal growth. Studies could link higher maternal glucose to an increase in infant birth weight as well as different extents of morbidity, among other things the incidence of congenital malformations, supporting the Hypothesis, that even moderately increased blood glucose in the absence of diabetes positively influences growth in the fetus.
Subsequently, alterations of Pedersen's Hypothesis took place: Nutrients other than sugar and their linkage to fetal overgrowth in diabetic pregnancy were taken into account, too, but the crucial role of the fetal hyperinsulinism and monitoring of motherly glucose was nevertheless stressed. Recent studies pointed out that diabetes in the mother could foster even more lasting effects on the child's health than previously thought, even raising the risk of obesity and type 2 diabetes.
Historical Cases
Various nutritional conditions, both times of scarcity and of abundance occurred time and again in different societies at different times, and thus in some cases epidemiological studies have exposed a correlation between the nutritional status of pregnant women and the health of their children or even grandchildren.
The Dutch Famine
Since low birth weight is associated with an increased risk of chronic diseases in later life, and inadequate maternal nutrition during pregnancy can contribute to restricted fetal growth, maternal under-nutrition may play a role in influencing long-term health outcomes.
The Dutch famine of 1944 or the "Hunger Winter" during World War II serves as an epidemiological study that is used to examine the effects of maternal under-nutrition during different gestational stages. This famine occurred over approximately five to six months in the western Netherlands and involved a significant reduction in food availability. The famine was imposed on a previously well-nourished population and the official daily ration for the general adult population gradually decreased from 1800 calories in December 1943 to 1400 calories in October 1944 to below 1000 calories in the late November 1944. Between December 1944 and April 1945, caloric intake further declined to approximately 400–800 calories per day. Although pregnant and lactating women were allocated additional food, these supplies became limited during the peak of the famine. In the early May 1945, the liberation of the Netherlands restored the food supply. The daily ration had increased to more than 2000 calories in June 1945. What distinguishes the Dutch famine as a study context is the well-defined time frame and geographic location, as well as the abrupt onset and resolution of food scarcity in a previously well-nourished population.
Research has linked maternal malnutrition during this period with limited intrauterine growth and an increased risk of chronic diseases in offspring later in life, including coronary heart disease. These observations are consistent with Barker's hypothesis, which suggests that early nutritional environments may have long-term effects on health outcomes.
The French Paradox
The French paradox regards the seemingly paradoxical fact that people living in France since many generations suffer from a relatively little incidence of heart disease, although the traditional French cuisine is high in saturated fatty acids.
One explanation suggested for the paradox is the potential impact of nutritional enhancements during pregnancy and the first months and years of life that would positively influence the health of following generations: After the defeat in the Franco-German War, a nutrition program for pregnant women and small children with the aim of strengthening future generations of soldiers was introduced by the French Government. This might be one explanation for positive health-outcomes in following generations.BBC News: Health French health mystery Size Matters: How Height Affects the Health, Happiness, and Success of Boys Other research indicates the potential influence of psychological and cultural factors regarding lower coronary heart disease deaths. Compared to other countries, college students in France associate food least with health and most with pleasure, which may lead to more positive attitudes surrounding food. Preliminary research suggests these French perspectives may correlate with a lower risk of developing preclinical stages of CHD. However, not all research supports these connections.
Recommendations for Pregnant Women
Gestation stages Gestation is the period of embryo development from conception to birth. Gestation is about 40 weeks in humans and is divided into three trimesters, each spanning 3 months. Gestational stages, on the other hand, are based on physiological fetal development, which include the germinal stage, embryonic stage and fetal stage.
Germinal stage is the stage from fertilization to about 2 weeks. The fertilized egg or the zygote becomes a blastocyst where the outer layer and the inner cell mass differentiate to form placenta and the fetus respectively. Implantation occurs at this stage where the blastocyst becomes buried in the endometrium.
Embryonic stage is approximately from 2 weeks to 8 weeks. It is also in this stage where the blastocyst develops into an embryo, where all major features of humans are present and operational by the end of this stage.