Foetal Motor Development

Introduction[edit | edit source]

The sensorimotor system of the foetus develops during gestation, which leads to patterned movements.[1] Foetal movements may be isolated (a specific pattern) or general (involve multiple body parts). In the later stages of pregnancy, these movement patterns become more complex.[1]

Major systems within the brain are entrenched prior to birth and facilitate the infant's emerging developmental skills. The motor and sensory systems are among the earliest systems to mature. They help the infant interact with and receive input from the world.[2]

First Motor Patterns[edit | edit source]

In the first few weeks of gestation, the most common motor patterns are spontaneous startles, general movements, isolated movements and twitches.[3] By week 13, a foetus's motor activity can include jaw movements, swallowing, yawning, and hand-face contact. During this period, handedness preference can be observed.[3]

Startles[edit | edit source]

Startles are whole body movements that begin in the limbs and spread to the neck and trunk.[4] Startles are brief in nature and begin at 8 weeks gestation.[4] [5] From this time, they increase in frequency until they reach a peak. There is a strong decrease in the number of startles up to 17 weeks gestation and a more gradual decrease throughout the rest of the pregnancy.[5]

General Movements[edit | edit source]

General movements are whole body movements that are slower and more complex than startles.[4] This movement pattern also emerges around 8 weeks and is characterised by their variety and fluency of movement. It has been argued that the displacement caused by a startle may lead to a chain of counter-reactive movements and trigger general movements.[5] By the 17th week of gestation, general movements appear spontaneously and do not necessarily follow a startle.[5][6]

Isolated movements[edit | edit source]

Isolated movements emerge shortly after general movements. These movements involve the unique sequencing of specific body parts. By the 14th week, isolated movements occur more frequently than general movements. Distinctive movements of the arms and legs start at the same time. However, arm movements occur more frequently than leg movements.[5]

Arm extension along with finger extension can be seen from 12 weeks gestation onwards. During this time, a foetus's hand consistently touches its face, head and occasionally its mouth. Distinctive finger movements appear around 13 weeks. By the third trimester, the foetus is able to squeeze and manipulate the umbilical cord.[4]

Slow or rapid isolated leg movements can occur bilaterally in an alternating pattern or unilaterally as a sporadic kick.[4]

Twitches[edit | edit source]

Twitches are specific spontaneous movements that occur during active sleep. This brief motor activity causes contractions of muscles, resulting in quick flexion or extension movements of the neck or limbs. Twitches can be seen in foetuses at around week 10-12, and they increase in frequency from weeks 15-16.[5]

Sensation[edit | edit source]

It can be difficult to determine when a foetus's motor activity is related to sensation. Spontaneous motor behaviour and reflexive reactions to touch emerge at around the same time, firstly around the mouth. Non-reflexive responses to stimulation occur as the sensory systems develop. It is possible to observe a foetus respond by moving to sound, light and touch disturbances. From around 21-33 weeks, foetuses can respond to maternal touch of the stomach.[5]

Random Movements[edit | edit source]

The first movements of a foetus are spontaneous and random in nature. Random movement can be referred to as motor babbling. While this motor activity is not goal-oriented, it allows the foetus to explore the environment around them and the significance of its movement on the environment. In the later stages of pregnancy, as the available space decreases, there is a reduction in the amount of movement.[5] Movements are confined to rotation and extension of the spine. This decrease in general movements coincides with an increase in facial movements. During this time, foetuses can be observed chewing, opening and closing the jaw and swallowing. This shift in movement patterns is seen as progression of normal foetal development.[3]

Goal-Directed Movements[edit | edit source]

Initial isolated movements tend to be towards body parts that are highly innervated such as the face. By 10 weeks gestation, a foetus regularly touches its face. As the pregnancy advances, arm movements towards the mouth increase. It has been suggested that foetuses might like to suck their thumb because both the mouth and thumb are richly innervated. Foetuses also have a preference for rubbing their eyelids, scratching their temples with their fingers and touching their feet, particularly the soles which are highly innervated.[5]

Goal-oriented behaviour can be seen when the foetus brings its arms to its mouth or eyes. Studies have shown that foetuses anticipate their hand coming to their mouth by opening their mouth before the hand arrives. Other studies report foetuses tend to slow down their arm speed as they bring it towards their eyes.[6] These goal-oriented movements tend to increase as gestation progresses.[5]

Foetal Posture[edit | edit source]

Many people assume the foetus is only in a flexed position in utero. However, a foetus changes its posture and position quite frequently. The posture of the foetus can be upside down, upright, sitting, prone or supine. This variability in movement is most common in the first half of the pregnancy. Alternating leg movements or somersaults typically initiate rotational motion along the longitudinal axis of the foetus. Additionally, during the first 20 weeks of gestation, foetuses can cross their legs and raise their hands and place them behind their head.[4]

Facial Expressions[edit | edit source]

In early pregnancy, complex sequential foetal eye movements can be observed. Between 23-26 weeks, blinking-like movements occur as the foetus opens and closes their eyelids. Clusters of rapid eye movements occur around 30 weeks onwards. In the last trimester of pregnancy, the foetus can be seen smiling, scowling and pouting.[4]

Stretches and Yawns[edit | edit source]

Yawning and stretching are initiated at around 12 weeks gestation. These are both complex motor patterns. Yawns begin with a wide opening of the jaw, a simultaneous caudal movement of the tongue and retroflexion of the head. This whole process takes around 9-13 seconds. Stretching involves the combination of head retroflexion, arm elevation in an externally rotated fashion and trunk extension. This complex movement pattern is always slow.[4]

Resources[edit | edit source]

References[edit | edit source]

  1. 1.0 1.1 Prechtl HF. R.(1986). Prenatal motor development. Motor Development.
  2. Thomason ME, Hect J, Waller R, Manning JH, Stacks AM, Beeghly M, Boeve JL, Wong K, Van Den Heuvel MI, Hernandez-Andrade E, Hassan SS. Prenatal neural origins of infant motor development: Associations between fetal brain and infant motor development. Development and psychopathology. 2018 Aug;30(3):763-72.
  3. 3.0 3.1 3.2 Borsani E, Della Vedova AM, Rezzani R, Rodella LF, Cristini C. Correlation between human nervous system development and acquisition of fetal skills: An overview. Brain and development. 2019 Mar 1;41(3):225-33.
  4. 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Einspieler C, Prayer D, Marschik PB. Fetal movements: the origin of human behaviour. Developmental Medicine & Child Neurology. 2021 Oct;63(10):1142-8.
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 Fagard J, Esseily R, Jacquey L, O’regan K, Somogyi E. Fetal origin of sensorimotor behavior. Frontiers in neurorobotics. 2018 May 23;12:23.
  6. 6.0 6.1 Hadders-Algra M. Early human motor development: From variation to the ability to vary and adapt. Neuroscience & Biobehavioral Reviews. 2018 Jul 1;90:411-27.