Pregnancy is accompanied by weight gain that varies between women, but an average of 9 and 12 kg for a woman with a normal BMI (between 19 and 24). This weight gain corresponds to the weight of the baby, its appendages (placenta, amniotic cavity), tissues whose mass increases during pregnancy (uterus, breasts), body fluids and fat reserves.

In terms of the general balance of the body and posture, this concentrated weight gain in the stomach causes a shift of the center of gravity forward. At the same time, the hormones of pregnancy (relaxin, estrogen, progesterone) cause ligament relaxation having an impact on the entire musculoskeletal system and can cause various pains in the lumbar region and the pubic symphysis in particular.

On the thermal level, under the effect of the secretion of progesterone, there is a noticeable increase in body temperature (> or = aÌ € 37 ° C) during the first trimester of pregnancy.

As for the immune system, pregnancy requires a state of immunosuppression so as not to reject the fetus which is assimilated to a “foreign body” by the mother’s body. Pregnant women are therefore more susceptible to infections.

Basal metabolism increases by an average of 20% in order to ensure the extra work of the heart and lungs and to provide the necessary energy for the fetus and its annexes. During the first two trimesters of pregnancy, the expectant mother will accumulate reserves, especially lipid, which will be mobilized in the third trimester to ensure the rapid growth of the baby. Energy requirements are therefore increased by around 300 kcal in the second trimester and 400 kcal in the third trimester.

In order to ensure a stable supply of glucose (the fetus’ main source of energy), different mechanisms are put in place: glycemia (blood glucose level) decreases, insulin secretion (hormone secreted by the pancreas and responsible for regulating blood sugar) increases, as does insulin resistance.

During pregnancy, the body is generally “over-diet”.

Cardiac output increases from the first trimester by about 20%, then by about 40% at the end of the sixth month of pregnancy. This results in an increase in heart rate of 10 to 15 beats / minute.

In the first and second trimesters, blood pressure decreases due to the phenomenon of vasodilation due to pregnancy hormones. Over the weeks, the uterus compresses the large vessels more and more and more particularly the inferior vena cava. There follows a decrease in venous return, and therefore hypotension.

At the respiratory level, oxygen needs are increased by 20 to 30% to meet the needs of the fetus and the placenta. In the mother-to-be, this results in hyperventilation: her respiratory rate and respiratory volume (quantity of air inhaled and exhaled with each respiratory movement) increase. The feeling of shortness of breath is therefore frequent.

From the start of pregnancy, there is hypervolemia, that is to say an increase in blood volume. The plasma volume increases steadily from 5 to 9 weeks of amenorrhea until 32 weeks before stabilizing. In the third trimester, the blood volume is thus 30 to 40% higher than outside pregnancy. This hypervolemia makes it possible to compensate for the increase in cardiac output, to cover the additional oxygen needs and to limit the consequences of a possible hemorrhage during childbirth.

The number of red blood cells also increases but proportionally less than that of the plasma volume, we therefore observe a decrease in the hemoglobin concentration responsible for a so-called physiological anemia of pregnancy.

In view of childbirth and delivery, two situations with a high risk of bleeding, most coagulation factors increase gradually during pregnancy.

During pregnancy, the size and weight of the kidneys increase. Their functioning is indeed increased in order to compensate for the increase in blood flow. The quantity of blood filtered by the kidneys of the pregnant woman is thus increased by 25 to 30%. Around the 20th week of pregnancy, the relaxing action of progesterone causes the kidney and ureters to dilate, promoting urinary stasis, which increases the risk of urinary tract infection. At the same time, the uterus compresses the bladder more and more, leading to a decrease in its size and as a result frequent urges to urinate (pollakiuria).

Stomach activity slows down due to a 40% decrease in gastric secretion, mobility and gastric tone. Associated with the decrease in the tone of the cardia (valve muscle ensuring the closure of the upper orifice of the stomach) under the effect of hormones, the increase in emptying time promotes gastric reflux (pyrosis) in pregnant women.

Transit time is also lengthened in the intestine. In question, the relaxing effect of progesterone which causes a less contraction of the smooth muscles of the intestines. The intestinal peristalsis (movements of the muscles allowing the food bolus to move forward in the intestines) is therefore less effective, which promotes constipation.

Hormonal impregnation as well as metabolic, immunological and circulatory changes can lead to different skin manifestations in the mother-to-be:

• hyperpigmentation, especially in women with a dark phototype. It mainly affects the most pigmented areas: the mammary areola, the nito-anal region, the peri-umbilical region and the abdominal midline (or linea nigra). On the face, this hyperpigmentation can be manifested by the mask of pregnancy (chloasma);
• new moles;
• stellate angiomas (small reddish or purplish skin lesions in the shape of a star);
• palmar erythema (red, hot hands);
• hyperpilosity;
• more intense sweating due to the increase in body temperature, which in turn occurs as a result of increased blood flow;
• acne due to overactive sebaceous glands;
• stretch marks due to mechanical distension due to weight gain and alteration of collagen fibers under the effect of pregnancy hormones.