1. Introduction

During pregnancy, women undergo a number of physiological changes [1,2] in order to achieve the normal development and health of the fetus. These changes also prepare the mother and baby for delivery.

The first change observed during pregnancy is weight gain. Following recommendations, for a woman with a normal weight (body mass index (BMI) between 19 and 24 kg/m²), gestational weight gain (GWG) should be between 11 and 16 kg. Physiological GWG is mainly due to fetus weight, the placenta, uterus, amniotic fluid, mammary gland, blood, and adipose tissue [3].

Moreover, hormonal changes are crucial throughout pregnancy [4]. On the one hand, there is an increase in the production of pre-existing hormones—mainly estrogens, progesterone, and prolactin—and the main producing tissues also change (the secretion becomes placental). On the other hand, specific hormones are synthesized by the placenta, like human chorionic gonadotropin (hCG).

These hormones play a fundamental role in ensuring the proper course of pregnancy and their concentration evolves throughout pregnancy. For example, we can cite the role of progesterone in the thickening and the vascularization of the uterine lining in anticipation of the implantation of an embryo.

Other important changes are cardiac and hematological alterations [5]. Plasma volume increases gradually by more than 40% throughout a normal pregnancy. This expansion is greater than the increase in red blood cell mass—there is a decrease in hemoglobin concentration, hematocrit, and red blood cell count. The platelet count decreases at the end of pregnancy, although it usually remains within normal limits. To cope with this increase in volume, cardiovascular adaptation, with peripheral vasodilatation, a decrease in systemic vascular resistance, and an increase in cardiac output of about 40% is observed.

In a supine position, the pressure of the gravid uterus on the inferior vena cava causes a decrease in venous return to the right heart and hypotension. Venous pressure in the lower limbs increases for the same reason. This explains the frequency of edemas observed in the lower limbs.

Oxygen demand in pregnant women increases dramatically by 20 to 30%. Increased progesterone levels lead to an increased respiratory rate and increased ventilation. This hyperventilation is accompanied by some anatomic changes, such as diaphragmatic elevation supported by the gravid uterus or the extension of the lower ribs. This explains why many pregnant women feel short of breath.

Other changes include alterations of the gastrointestinal system with frequent nausea and vomiting during the first trimester, correlating with the hCG peak, gastroesophageal reflux, or constipation. The renal and urinary tracts are also affected by pregnancy [2].

A breastfeeding mother provides all the hydration and nutrients that a growing baby needs for the first 4–6 months of life. During pregnancy, the body prepares for lactation by stimulating the growth and development of branched lactiferous ducts and lactocyte-lined alveoli that secrete milk by creating colostrum. These functions are due to the actions of estrogen, growth hormone, cortisol, and prolactin. In addition, in response to progesterone, clusters of mammary alveoli bud from the ducts and dilate toward the chest wall. After childbirth, breastfeeding triggers the release of oxytocin, which stimulates myoepithelial cells to squeeze milk from the alveoli. Breast milk then flows to the pores of the nipple for consumption by the infant [6].

The nutritional needs of women increase during pregnancy and breastfeeding to support all of these changes, prepare the body for delivery and for breastfeeding, and to ensure the normal development of the fetus/baby.

Mainly provided by a balanced diet, micronutrients (i.e., vitamins and minerals) and omega-3 fatty acids are essential for many cellular and metabolic activities (cell differentiation, proliferation, hemoglobin production, transport oxygen, and mineralization, etc.). The current intake of vitamins, minerals, and omega-3 fatty acids from foods across Europe limit the risk of severe deficiencies [7]. However, some deficiencies have been highlighted as particularly affecting pregnant women, such as vitamin D or iron deficiencies [8,9,10]. This is why pregnant women should be vigilant about their food intake so that they maintain adequate levels of micronutrients. Vitamins, minerals, and omega-3 fatty acids play an important role during pregnancy: ensuring the appropriate progress of a normal pregnancy in order to support the mother through the common discomforts of pregnancy or to prevent pregnancy complications. In addition, even though lactation is considered successful when the breastfed baby gains an appropriate weight, it is recommended that women continue to take a prenatal vitamin daily while breastfeeding.

Faced with changes related to pregnancy, the needs of the fetus, and the preparation of the body for breastfeeding, the nutritional needs of pregnant women can be adapted either by the implementation of an adapted and balanced diet or by supplementation. Specific nutritional intakes can also correct some common clinical signs of pregnancy.