Fetal movement
Encyclopedia
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
caused by its own muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
activity. Locomotor activity begins during the late embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
logical stage, and changes in nature throughout development. Muscles begin to move as soon as they are innervated
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
. These first movements are not reflexive, but arise from self-generated nerve impulses originating in the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
. As the nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
matures, muscles can move in response to stimuli.
Generally speaking, fetal motility can be classified as either elicited or spontaneous, and spontaneous movements may be triggered by either the spine or the brain. Whether a movement is supraspinally determined can be inferred by comparison to movements of an anencephalic fetus.
Although the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
begins to beat on the 23rd day after conception
Fertilisation
Fertilisation is the fusion of gametes to produce a new organism. In animals, the process involves the fusion of an ovum with a sperm, which eventually leads to the development of an embryo...
, this article primarily deals with voluntary and reflex
Reflex
A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...
movements. Ages are given as age from fertilization rather than as gestational age
Gestational age
Gestational age relates to the age of an embryo or fetus . There is some ambiguity in how it is defined:*In embryology, gestational age is the time elapsed since conception. This interval is also termed fertilisation age....
.
Some sources contend that there is no voluntary movement until after birth. Other sources say that purposive movement begins months earlier. 3D ultrasound
3D ultrasound
3D ultrasound is a medical ultrasound technique, often used in obstetric ultrasonography , providing three dimensional images of the fetus....
has been used to create motion pictures of fetal movement, which are called "4D ultrasound".
Embryonic Stage
Even before the fetal stage begins, a six-week-old human embryoEmbryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
can arch its back and neck. By seven weeks, movement in the arms and legs can be detected by ultrasound
Medical ultrasonography
Diagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...
.
Fetal Stage
The parts of the fetal brain that control movement will not fully form until late in the second trimester, and the first part of the third trimester. Control of movement is limited at birth, and purposeful voluntary movements develop during the long period up until puberty. According to an overview produced by the Royal College of Physicians of EdinburghRoyal College of Physicians of Edinburgh
The Royal College of Physicians of Edinburgh was established in the 17th century. While the RCPE is based in Edinburgh, it is by no means just a Scottish professional body - more than half of its 7,700 Fellows, Members, Associates and Affiliates live and practice medicine outside Scotland, in 86...
, purposive movement begins at about 18 weeks, gradually replacing reflex movements, and purposeful voluntary movements then develop further after birth.
In these early movements, the limbs move together; they begin to move independently by the ninth week as the controlling neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
s in the spinal cord develop. At week 11, the fetus can open its mouth and suck its fingers; at week 12, it begins to swallow
Swallowing
Swallowing, known scientifically as deglutition, is the process in the human or animal body that makes something pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis. If this fails and the object goes through the trachea, then choking or pulmonary aspiration...
amniotic fluid
Amniotic fluid
Amniotic fluid or liquor amnii is the nourishing and protecting liquid contained by the amniotic sac of a pregnant woman.- Development of amniotic fluid :...
.
In addition to sideward bendings of the head, complex and generalized movements occur at the beginning of the fetal stage, with movements and startles that involve the whole body. Movement of hands, hips and knees have been observed at nine weeks, stretches and yawns at ten weeks, and isolated limb movements beginning shortly thereafter.
Second trimester
By about the twelfth week, the fetus is able to kick and curl its toes, and may grasp its feet or scratch itself with its fingernails. It can also move in response to a touchSomatosensory system
The somatosensory system is a diverse sensory system composed of the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception . The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal...
on its skin. Also starting about week 12, the thoracic diaphragm
Thoracic diaphragm
In the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm , is a sheet of internal skeletal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration...
moves up and down as if the fetus were breathing, but this movement disappears about week 16 and does not resume until the third trimester.
Movements such as kicking continue, and the mother usually feels movement for the first time, an event called quickening
Quickening
Quickening is the earliest perception of fetal movement by a mother during pregnancy Quickening may also refer to:* Quickening , Final Fantasy XIIs incarnation of "Limit Breaks"...
, during the fifth month. Around this time, limb movements become more complex, with flexing of the joint
Joint
A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...
s and ribs. This activity assists with proper joint development. Women who have already given birth have more relaxed uterine muscles that are consequently more sensitive to fetal motion, and for them fetal motion can sometimes be felt as early as 14 weeks.
By about week 21, the fetus begins to develop a regular schedule of movement. The startle reflex
Moro reflex
The Moro reflex, which is distinct from the startle reflex, is one of the infantile reflexes.It may be observed in incomplete form in premature birth after the 28th week of gestation, and is usually present in complete form by week 34...
is present in half of all fetuses by week 24 and in all fetuses by week 28. Movement is restricted around this time because the fetus has grown so large it has little space for kicking or changing body position.
Third trimester
In later pregnancy, a complex motion called "stepping" develops. This movement consists of circular "bicycling" motion of legs, which helps the fetus move to a head-down positionPelvimetry
Pelvimetry is the assessment of the female pelvis in relation to the birth of a baby. Traditional obstetrical services relied heavily on pelvimetry in the conduct of delivery in order to decide if natural or operative vaginal delivery was possible or if and when to use a cesarean...
in preparation for birth.
Variation in activity level
Fetuses aged 14 to 18 weeks show a pronounced circadian rhythmCircadian rhythm
A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...
in their activity level, which can be detected both by fetal electrocardiogram
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
and by measuring locomotor activity. Active and quiet periods for the fetus do not correspond to those of the mother; fetuses are most active from 9 a.m. to 2 p.m. and again from 7 p.m. to 4 a.m. During the last four to six weeks before birth
Birth
Birth is the act or process of bearing or bringing forth offspring. The offspring is brought forth from the mother. The time of human birth is defined as the time at which the fetus comes out of the mother's womb into the world...
, most of the fetuses' kicking and jabbing movements occur while it is sleep
Sleep
Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than...
ing lightly.
Monitoring fetal movement
After quickening, a pregnant woman may choose to count the number and types of movements she feels her fetus make. This tally is informally known as a kick count. The American Pregnancy Association states that advantages of conducting kick counts range from giving a pregnant woman an opportunity to bond with her baby to reducing the risk of stillbirthStillbirth
A stillbirth occurs when a fetus has died in the uterus. The Australian definition specifies that fetal death is termed a stillbirth after 20 weeks gestation or the fetus weighs more than . Once the fetus has died the mother still has contractions and remains undelivered. The term is often used in...
; kick counts are especially recommended in high risk pregnancies.
To make a kick count, a woman finds a comfortable position, such as sitting upright with her back supported or lying on her left side (which maximizes blood flow to the fetus), and times how long it takes to feel at least ten movements such as kicks, flutters, or rolls. Ideally, ten movements should be felt within two hours, although often that number is reached in a much shorter period. The results can be recorded to reveal the pattern of movement. Significant changes in this pattern can notify a woman of a problem with her fetus, allowing her to notify her practitioner
Obstetrics
Obstetrics is the medical specialty dealing with the care of all women's reproductive tracts and their children during pregnancy , childbirth and the postnatal period...
early in the case of a problem.