From the Guidelines
Fetal practice breathing, also known as Fetal Breathing Movements (FBM), refers to the rhythmic movements of the fetus's chest and diaphragm that mimic breathing movements, and is assessed as part of the Biophysical Profile (BPP) if there is at least one episode continuing for 30 seconds within the 30-minute BPP 1.
Definition and Importance
Fetal practice breathing is a critical aspect of fetal development, as it helps strengthen the respiratory muscles, stimulate lung growth, and prepare the lungs for air breathing after birth. These movements typically begin around 10-11 weeks of gestation but become more regular and pronounced after about 28 weeks. During practice breathing, the fetus moves amniotic fluid in and out of the developing lungs, which is crucial for proper lung development and maturation.
Assessment and Monitoring
Healthcare providers may monitor these movements during ultrasounds as part of assessing fetal well-being, particularly in high-risk pregnancies. The BPP consists of four ultrasound-based assessments, including fetal breathing movements, discrete body movements, fetal tone, and amniotic fluid volume 1. A fetal breathing movement meets criteria if there is at least one episode continuing for 30 seconds within the 30-minute BPP. Decreased fetal breathing movements can sometimes indicate fetal distress or developmental issues, though they naturally decrease shortly before labor begins.
Clinical Significance
The assessment of fetal breathing movements is essential for evaluating fetal well-being and identifying potential complications. The BPP score, which includes the assessment of fetal breathing movements, can help healthcare providers identify fetuses at risk of compromise and guide management decisions. A composite score of 8 or 10 is normal, 6 is equivocal, and 4 or less is abnormal 1.
Key Points
- Fetal practice breathing is an essential aspect of fetal development and preparation for air breathing after birth.
- The BPP assesses fetal breathing movements, among other parameters, to evaluate fetal well-being.
- Decreased fetal breathing movements can indicate fetal distress or developmental issues.
- The BPP score can help healthcare providers identify fetuses at risk of compromise and guide management decisions 1.
From the Research
Definition and Purpose of Fetal Breathing Movements
- Fetal Breathing Movements (FBM) are a feature of normal fetal life, used clinically to assess fetal wellbeing 2.
- FBM help maintain the high level of lung expansion essential for normal growth and structural maturation of the fetal lungs 2.
- The movements oppose lung recoil, resisting the escape of lung liquid via the trachea during 'apnoeic' periods 2.
Patterns and Characteristics of Fetal Breathing Movements
- There are two patterns of FBM: rapid, irregular episodic movements and sporadic, slow, deep inspiratory movements 3.
- The first pattern represents normal fetal respiratory activity, occurring during rapid eye movements (REM) sleep, and is unrelated to changes in blood gases and pH values 3.
- FBM may produce intrathoracic pressure swings and are independent of Hering-Breuer reflexes 3.
Factors Influencing Fetal Breathing Movements
- FBM can be inhibited by fetal hypoxaemia, hypoglycaemia, maternal alcohol consumption, maternal smoking, intra-amniotic infection, and maternal consumption of sedatives or narcotic drugs 2.
- Certain drugs, such as aminophylline, hexoprenaline, conjugated estrogens, and betamethasone, can elicit or enhance FBM 3.
Development and Observation of Fetal Breathing Movements
- FBM have been observed in fetuses of many species, including humans, and aid in lung development, strengthen respiratory muscles, and fine-tune the neural circuitry that drives breathing 4, 5.
- In mice, FBM commence on embryonic day 16 and increase in frequency with age 5.
- Fetal hiccups, considered a programmed isometric inspiratory muscle exercise, emerge as early as nine weeks post-conception and can be assessed using magnetographic techniques 6.