There are quite a few biochemical changes during pregnancy, and it is one of the most nutritionally demanding times in a woman’s life since nutrients must be consumed to meet the demands of two beings: the mother and the growing fetus, ensuring the health and well-being of both.
For certain nutrients, the fetus’ nutritional status is maintained at the expense of the mother’s, for others, both compete on equal terms, and for others, the effects of a shortfall are far harsher for the fetus than for the mother. The dietary requirements during the various stages of gestation might be defined in a schematic and summary manner as follows:
The first trimester: It is a period of extremely fast fetal growth, thus any food shortage at this time might result in irreparable changes in the fetus. As a result, a high-quality nutritional intake is necessary, with little variance in calorie requirements. Foods that are high in nutrients are essential.
The second trimester: Fetal growth, particularly bone development, continues. This is the stage at which the maternal fat deposit is formed, ensuring sufficient breastfeeding. Caloric intake is critical since calorie limitation during this period will jeopardize future breastfeeding.
The third trimester three: The fetus multiplies its weight by 5 in the last months, increasing the requirement for energy and nutrients.
Physiological and Biochemical Changes during Pregnancy
A woman goes through a series of physiological and biochemical changes during pregnancy, that are adaptations aimed to carry the pregnancy to term and prepare her for the following stage: breastfeeding. These modifications allow appropriate nutrition even at lower consumption than would be required to meet feto-maternal needs.
Hormonal Changes during Pregnancy
The hormonal changes during pregnancy allow nutrients to be directed towards the placenta in order to favor their transfer to the baby and support its development. Steroid hormones, chorionic gonadotropin, and placental lactogen are the hormones that have the largest impact on mother and child metabolism.
During the early part of pregnancy, higher estrogen and progesterone stimulate pancreatic ß-cells, which respond by producing more insulin, which increases glycogen storage and peripheral glucose use, resulting in anabolic alterations.
Increased lipid production, lipolysis inhibition, and adipocyte hypertrophy all contribute to fat formation. Lipids are mobilized and used throughout the second part of the pregnancy when placental lactogen rises.
Blood Volume Changes during Pregnancy
Blood volume increases by 50% during pregnancy due to the expansion of plasma volume and the number of red blood cells. This causes hemodilution, which results in a 20% drop in hemoglobin levels and a 15% drop in hematocrit. There is also a drop in plasma albumin concentron, which adds to extracellular fluid buildup and is another one of the physiological changes during pregnancy.
Lipoproteins, particularly very low density lipoproteins (VLDL), see a rise. Cholesterol and free fatty acids rise, particularly arachidonic acid and DHEA, owing to enhanced mobilization of maternal deposits; long-chain fatty acids, fall during pregnancy due to increased fetal absorption.
The heart, on the other hand, grows in size, increasing cardiac output to around 1.5 l/min; heart rate increases by about 15 beats/min while systolic blood pressure remains steady; diastolic blood pressure declines in early pregnancy and progressively rises towards the 26-28th week.
Other Physiological Changes during Pregnancy
The action of progesterone on the smooth muscle causes a slowdown of peristaltic movements throughout the digestive system, which is meant to aid nutritional absorption but can result in constipation, which is exacerbated in the last stages of pregnancy due to direct uterine pressure on the rectum.
The hormonal situation causes nausea and vomiting in the first trimester, which may affect intake; later on, the sensation of appetite may increase, which may lead to excessive weight gain; and it is also common to develop aversions and preferences to certain foods, a phenomenon that, while obvious, has no physiological explanation.
It has been adjusted to remove the byproducts of maternal catabolism as well as other chemicals originating in the fetus and placenta. The rate of glomerular filtration rises by up to 50%, resulting in increased elimination of glucose (10 times normal), amino acids (2-7 times normal), and water-soluble vitamins.
Changes to Body Weight
Body weight growth is a good sign of prenatal development and a good measure for determining the necessary changes in energy and food intake to ensure a healthy pregnancy.
The gain will be determined by the beginning maternal weight, and it is suggested that it be between 9-12 kilos in women of normal weight; both lower and larger rises are associated with increased perinatal morbidity and death.
Women with low pregestational weight (BMI less than 19.5) should gain 12-15 kg, while those who are overweight (BMI 25-30) should gain 6-9 kg; in general, women of short stature should stick to the lower limits of the recommendations, while adolescent pregnant women should always stick to the upper limits. In the event of multiple pregnancy, regardless of pregestational weight, the increase should be between 14-18 kg for twins and at least 25 kg for triplets.
The pattern of weight growth is just as essential as the quantity itself. Thus, weight may be maintained or even lost during the first trimester, however it is most normal to gain between 1 and 4 kg. In the second and third trimesters, the average growth for women of normal weight is 0.5 kg per week; this figure should be 800 g in those who were pregestationally underweight and around 300 g in those who were initially overweight.
Water accounts for 62% of the overall weight increase during pregnancy, 30% for fat, and 8% for protein. A rise of less than 7 kg is regarded to represent fat reserve consumption, but a gain of more than 13 kg indicates an excessive buildup of adipocyte deposits.
The fetus contributes just 25% of overall weight increase, 60% of total protein absorbed, and 10% of total fat acquired. The remaining adipose tissue acquired by the mother will be critical in meeting the demands of the fetus at the conclusion of gestation and, as previously stated, throughout nursing.