Fetal Breathing Movements (FBMs) are often referred to as “practice breathing.” This activity is a normal and expected part of late-stage pregnancy development. Understanding the true nature of these movements is key to knowing whether they offer any clue about when your baby might arrive.
What Are Fetal Breathing Movements
Fetal Breathing Movements are rhythmic contractions of the diaphragm and the intercostal muscles. The fetus is not actually inhaling air, as oxygen is supplied continuously through the placenta via the umbilical cord. Instead, the baby draws amniotic fluid into and out of the lungs, mimicking the action of breathing. This activity exercises the respiratory muscles and promotes the development of lung tissue in preparation for life outside the womb.
These movements are a long-term feature of fetal development, not a last-minute preparation for labor. FBMs can be observed as early as 10 to 16.5 weeks of gestation, though they typically become more organized and frequent as the pregnancy progresses. By the third trimester, the fetus engages in these practice sessions for a significant portion of the day. The continuous practice helps ensure the baby’s lungs and associated muscles are ready to take their first independent breath at birth.
The Predictive Value of Practice Breathing
While Fetal Breathing Movements are a positive sign of well-being, they are not considered a reliable indicator that labor is imminent. The frequency of FBMs is more closely related to the baby’s current physiological state than to the onset of uterine contractions. These movements are known to be cyclic, often ceasing during periods of deep fetal sleep and resuming during active wake cycles.
The frequency of FBMs can also be influenced by maternal factors, such as blood glucose levels, which often increase the movement rate following a meal. If a healthcare provider monitors these movements using ultrasound, they are primarily assessing the baby’s overall health and central nervous system function, not attempting to predict the exact day of delivery. Therefore, experiencing a period of increased “practice breathing” should not be interpreted as a sign that labor is about to begin.
Other Signs That Labor May Be Near
Expectant parents should monitor for distinct physiological changes that are verifiably associated with the approach of labor. One common change is “lightening,” which occurs when the baby’s head settles lower into the pelvis. This often results in less pressure on the lungs and easier breathing for the pregnant person. This dropping can happen a few weeks before labor in a first pregnancy, or sometimes not until labor has already started in subsequent pregnancies.
Another verifiable sign is the expulsion of the mucus plug, sometimes accompanied by a small amount of blood known as the “bloody show.” The mucus plug seals the cervix during pregnancy, and its release indicates that the cervix is beginning to soften and dilate. This sign may occur days or weeks before true labor begins, or it may happen right before or during active labor.
The most definitive signs involve uterine contractions and the rupture of membranes. Distinguishing true labor from Braxton Hicks contractions involves tracking their regularity, duration, and intensity. True labor contractions follow a pattern, become progressively stronger, and do not stop when you change position. The rupture of membranes, or “water breaking,” is a direct signal that labor is likely to follow soon. This event may be a sudden gush or a slow trickle of amniotic fluid.