Very early in pregnancy, a pregnant woman can quickly feel short of breath at the slightest effort. As a result of various physiological changes necessary to meet the needs of the baby, this shortness of breath during pregnancy is quite normal.

During pregnancy, several adaptations are necessary to meet the increased metabolic needs of the mother and the fetus. Directly linked to pregnancy hormones, some of these physiological changes cause shortness of breath in the mother-to-be, long before the uterus compresses her diaphragm.

To meet the oxygen needs of the placenta and the fetus estimated at 20 to 30%, there is indeed an overall increase in cardiac and respiratory work. The blood volume increases (hypervolemia) and cardiac output increases by approximately 30 to 50%, causing at the respiratory level an increase in pulmonary blood flow and oxygen uptake per minute. The strong secretion of progesterone causes an increase in respiratory flow, leading to hyperventilation. The respiratory rate increases and can thus reach up to 16 breaths per minute, causing a feeling of shortness of breath on exertion, or even at rest. It is estimated that one in two pregnant women has dyspnea (1).

From 10-12 weeks, the respiratory system of the mother-to-be changes significantly to adapt to these different modifications, and to the future volume of the uterus: the lower ribs widen, the level of the diaphragm rises, the diameter of the thorax increases, the abdominal muscles become less toned, the respiratory tree becomes congested.

Strictly speaking, the baby does not breathe in utero; it will only do so at birth. During pregnancy, the placenta plays the role of “fetal lung”: it brings oxygen to the fetus and evacuates fetal carbon dioxide.

Fetal distress, i.e. the baby’s lack of oxygenation (anoxia), is not related to the mother’s shortness of breath. It appears during intrauterine growth retardation (IUGR) detected on ultrasound, and can have various origins: placental pathology, pathology in the mother (cardiac problem, hematology, gestational diabetes, smoking, etc.), fetal malformation, infection.

As the tendency to shortness of breath during pregnancy is physiological, it is difficult to avoid it. The future mother must however take care, especially at the end of pregnancy, by limiting physical efforts.

In the event of a feeling of suffocation, it is possible to do this exercise to “free” the rib cage: lying on your back with your legs bent, inhale while raising your arms above your head then exhale while bringing your arms back. along the body. Repeat over several slow breaths (2).

Breathing exercises, sophrology exercises, prenatal yoga can also help the expectant mother to limit this feeling of shortness of breath that the psychological component can also accentuate.

As the weeks of pregnancy progress, the organs are used more and more and the baby needs more oxygen. The body of the mother-to-be produces more carbon dioxide, and it must also eliminate that of the baby. The heart and lungs therefore work harder.

At the end of pregnancy, a mechanical factor is added and increases the risk of shortness of breath by reducing the size of the rib cage. As the uterus squeezes the diaphragm more and more, the lungs have less room to inflate and lung capacity decreases. Weight gain can also cause a feeling of heaviness and accentuate shortness of breath, especially during exertion (climbing stairs, walking, etc.).

Iron deficiency anemia (due to iron deficiency) can also cause shortness of breath on exertion, and sometimes even at rest.

In isolation, shortness of breath is not a warning sign and should not cause concern during pregnancy.

However, if it appears suddenly, if it is associated with pain in the calves in particular, it is advisable to consult in order to rule out any risk of phlebitis.

At the end of pregnancy, if this shortness of breath is accompanied by dizziness, headaches, edema, palpitations, abdominal pain, visual disturbances (sensation of flies in front of the eyes), palpitations, an emergency consultation is required in order to detect pregnancy-induced hypertension, which can be serious at the end of pregnancy.