Fetal Growth And Development Pdf

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While you might think of child development as something that begins during infancy, the prenatal period is also considered an important part of the developmental process. Prenatal development is a time of remarkable change that helps set the stage for future psychological development. The brain develops over the course of the prenatal period, but it will continue to go through more changes during the early years of childhood.

The perinatal literature includes several potentially confusing and controversial terms and concepts related to fetal size and growth. This article discusses fetal growth from an obstetric perspective and addresses various issues including the physiologic mechanisms that determine fetal growth trajectories, known risk factors for abnormal fetal growth, diagnostic and prognostic issues related to restricted and excessive growth and temporal trends in fetal growth. Also addressed are distinctions between fetal growth 'standards' and fetal growth 'references', and between fetal growth charts based on estimated fetal weight vs those based on birth weight.

Fetal Development: Stages of Growth

Prenatal development starts with fertilization , in the germinal stage of embryonic development, and continues in fetal development until birth. In human pregnancy , prenatal development is also called antenatal development. The development of the human embryo follows fertilization , and continues as fetal development. By the end of the tenth week of gestational age the embryo has acquired its basic form and is referred to as a fetus.

The next period is that of fetal development where many organs become fully developed. This fetal period is described both topically by organ and chronologically by time with major occurrences being listed by gestational age. The very early stages of embryonic development are the same in all mammals. Later stages of development across all taxa of animals and the length of gestation vary.

Different terms are used to describe prenatal development , meaning development before birth. The perinatal period from Greek peri , "about, around" and Latin nasci "to be born" is "around the time of birth ". In developed countries and at facilities where expert neonatal care is available, it is considered from 22 completed weeks usually about days of gestation the time when birth weight is normally g to 7 completed days after birth.

Fertilization marks the first germinal stage of embryonic development. When semen is released into the vagina , the spermatozoa travel through the cervix and body of the uterus and into the fallopian tubes where fertilization usually takes place. Many sperm cells are released with the possibility of just one managing to adhere to and enter the thick protective layer surrounding the egg cell ovum. The first sperm cell to successfully penetrate the egg cell donates its genetic material DNA to combine with the DNA of the egg cell resulting in a new organism called the zygote.

The term "conception" refers variably to either fertilization or to formation of the conceptus after its implantation in the uterus, and this terminology is controversial. The zygote will develop into a male if the egg is fertilized by a sperm that carries a Y chromosome , or a female if the sperm carries an X chromosome. In contrast, the mitochondrial DNA of the zygote comes entirely from the egg cell. Following fertilization the embryonic stage of development continues until the end of the 10th week gestational age 8th week fertilization age.

The first two weeks from fertilization is also referred to as the germinal stage or preembryonic stage. The zygote spends the next few days traveling down the fallopian tube dividing several times to form a ball of cells called a morula. Further cellular division is accompanied by the formation of a small cavity between the cells. This stage is called a blastocyst. Up to this point there is no growth in the overall size of the embryo, as it is confined within a glycoprotein shell, known as the zona pellucida.

Instead, each division produces successively smaller cells. The blastocyst reaches the uterus at roughly the fifth day after fertilization.

It is here that lysis of the zona pellucida occurs. This process is analogous to zona hatching , a term that refers to the emergence of the blastocyst from the zona pellucida, when incubated in vitro. This allows the trophectoderm cells of the blastocyst to come into contact with, and adhere to, the endometrial cells of the uterus.

The trophectoderm will eventually give rise to extra-embryonic structures, such as the placenta and the membranes. The embryo becomes embedded in the endometrium in a process called implantation. In most successful pregnancies, the embryo implants 8 to 10 days after ovulation.

Rapid growth occurs and the embryo's main features begin to take form. This process is called differentiation , which produces the varied cell types such as blood cells, kidney cells, and nerve cells. A spontaneous abortion, or miscarriage , in the first trimester of pregnancy is usually [8] due to major genetic mistakes or abnormalities in the developing embryo. During this critical period most of the first trimester , the developing embryo is also susceptible to toxic exposures, such as:.

The embryo passes through 3 phases of acquisition of nutrition from the mother: [9]. Fetal development is the third of the three stages of prenatal development, following from the initial germinal stage preembryonic stage , and stage of embryonic development.

These stages are also referred to in pregnancy as terms or trimesters. From the 10th week of gestation 8th week of development , the developing organism is called a fetus.

All major structures are already formed in the fetus, but they continue to grow and develop. Since the precursors of all the major organs are created by this time, the fetal period is described both by organ and by a list of changes by weeks of gestational age. Because the precursors of the organs are now formed, the fetus is not as sensitive to damage from environmental exposure as the embryo was.

Instead, toxic exposure often causes physiological abnormalities or minor congenital malformation. Development continues throughout the life of the fetus and through into life after birth. Significant changes occur to many systems in the period after birth as they adapt to life outside the uterus. Hematopoiesis first takes place in the yolk sac. The function is transferred to the liver by the 10th week of gestation and to the spleen and bone marrow beyond that. Megaloblastic red blood cells are produced early in development, which become normoblastic near term.

Life span of prenatal RBCs is 80 days. Rh antigen appears at about 40 days of gestation. The fetus starts producing leukocytes at 2 months gestational age, mainly from the thymus and the spleen. Lymphocytes derived from the thymus are called T lymphocytes T cells , whereas those derived from bone marrow are called B lymphocytes B cells. Both of these populations of lymphocytes have short-lived and long-lived groups.

Short-lived T cells usually reside in thymus, bone marrow and spleen; whereas long-lived T cells reside in the blood stream. Plasma cells are derived from B cells and their life in fetal blood is 0. The thyroid is the first gland to develop in the embryo at the 4th week of gestation. Insulin secretion in the fetus starts around the 12th week of gestation.

Initial knowledge of the effects of prenatal experience on later neuropsychological development originates from the Dutch Famine Study, which researched the cognitive development of individuals born after the Dutch famine of — There is evidence that the acquisition of language begins in the prenatal stage. After 26 weeks of gestation, the peripheral auditory system is already fully formed.

Growth rate of fetus is linear up to 37 weeks of gestation, after which it plateaus. A baby born within the normal range of weight for that gestational age is known as appropriate for gestational age AGA.

An abnormally slow growth rate results in the infant being small for gestational age , and, on the other hand, an abnormally large growth rate results in the infant being large for gestational age. A slow growth rate and preterm birth are the two factors that can cause a low birth weight. Low birth weight below grams can slightly increase the likelihood of schizophrenia.

The growth rate can be roughly correlated with the fundal height which can be estimated by abdominal palpation. More exact measurements can be performed with obstetric ultrasonography. Intrauterine growth restriction is one of the causes of low birth weight associated with over half of neonatal deaths.

Poverty has been linked to poor prenatal care and has been an influence on prenatal development. Women in poverty are more likely to have children at a younger age, which results in low birth weight.

Women between the ages of 16 and 35 have a healthier environment for a fetus than women under 16 or over Women over 35 are more inclined to have a longer labor period, which could potentially result in death of the mother or fetus.

Women under 16 and over 35 have a higher risk of preterm labor premature baby , and this risk increases for women in poverty, women who take drugs, and women who smoke. Young mothers are more likely to engage in high risk behaviors, such as using alcohol, drugs, or smoking, resulting in negative consequences for the fetus. There is a risk of Down syndrome for infants born to those aged over 40 years. Young teenaged mothers younger than 16 and mothers over 35 are more exposed to the risks of miscarriages, premature births, and birth defects.

An estimated 5 percent of fetuses in the United States are exposed to illicit drug use during pregnancy. Resent research display that there is a correlation between fine motor skills and prenatal risk factors such as the use of psychoactive substances and signs of abortion during pregnancy.

As well as perinatal risk factors such as gestation time, duration of delivery, birth weight and postnatal risk factors such as constant falls. When using cannabis , there is a greater risk of birth defects, low birth weight, and a higher rate of death in infants or stillbirths. It can also lead to low birth weight, a shortened gestational period and complications in delivery.

Opioids including heroin will cause interrupted fetal development, stillbirths, and can lead to numerous birth defects. Heroin can also result in premature delivery, creates a higher risk of miscarriages, result in facial abnormalities and head size, and create gastrointestinal abnormalities in the fetus.

There is an increased risk for SIDS, dysfunction in the central nervous system, and neurological dysfunctions including tremors, sleep problems, and seizures. The fetus is also put at a great risk for low birth weight and respiratory problems.

Cocaine use results in a smaller brain, which results in learning disabilities for the fetus. Cocaine puts the fetus at a higher risk of being stillborn or premature. Cocaine use also results in low birthweight, damage to the central nervous system, and motor dysfunction. Prenatal methamphetamine exposure has shown to negatively impact brain development and behavioral functioning.

A study further investigated neurocognitive and neurodevelopmental effects of prenatal methamphetamine exposure. This study had two groups, one containing children who were prenatally exposed to methamphetamine but no other illicit drugs and one containing children who met diagnosis criteria for ADHD but were not prenatally exposed to any illicit substance.

Both groups of children completed intelligence measures to compute an IQ. Study results showed that the prenatally exposed children performed lower on the intelligence measures than their non-exposed peers with ADHD.

The study results also suggest that prenatal exposure to methamphetamine may negatively impact processing speed as children develop. Maternal alcohol use leads to disruptions of the fetus's brain development, interferes with the fetus's cell development and organization, and affects the maturation of the central nervous system.

Even small amounts of alcohol use can cause lower height, weight and head size at birth and higher aggressiveness and lower intelligence during childhood.

Children with FASD have a variety of distinctive facial features, heart problems, and cognitive problems such as developmental disabilities, attention difficulties, and memory deficits. Tobacco smoking during pregnancy exposes the fetus to nicotine, tar, and carbon monoxide.

Human Fetal Growth and Development

Prior, D. Heifers were fed three dietary energy levels to provide for gains of 0 to. Animals on each dietary treatment were slaughtered at 90, , , , , and days of gestation in a study to characterize bovine fetal growth as a basis for assessing the stage of gestation at which fetal development might be altered without suppressing neonatal growth. Initial instantaneous growth rate weight was 7. The instantaneous rate of increase of fetal weight reached a maximum at days of gestation and declined thereafter. The rate of DNA synthesis reached a. Correlations among fetal weight, fetal fluid weight, cotyledon area, placental weight and uterine weight were high and positive, but there was no indication that fetal growth can be effectively mediated indirectly by restriction of uterine or placental development.

Fetal growth and development: the role of nutrition and other factors

Health care providers who see newcomer families have a pivotal role to play in identifying and initiating early treatment for developmental disabilities. Developmental disabilities may last a lifetime but early recognition of their existence, a timely diagnosis and an appropriate treatment plan can make a difference for the children and families involved. When seeing newcomer families, recognize that risk factors are cumulative. In many parts of the world, suboptimal conditions and care during pregnancy and childbirth can have a range of impacts on developmental health. Developmental disabilities in immigrant and refugee children do not always have a known cause.

Human Fetal Growth and Development

Prenatal development is highly influenced by the inheritance, expression, and regulation of genes.

Prenatal development starts with fertilization , in the germinal stage of embryonic development, and continues in fetal development until birth. In human pregnancy , prenatal development is also called antenatal development. The development of the human embryo follows fertilization , and continues as fetal development. By the end of the tenth week of gestational age the embryo has acquired its basic form and is referred to as a fetus.

Normal fetal growth is a critical component for a healthy pregnancy and for ensuring the health and well-being of infants throughout childhood and adolescence. Pivotal to understanding the dynamics of human fetal growth and to defining normal and abnormal fetal growth is the development of standards for fetal anthropometric parameters, measured longitudinally throughout gestation. Such measures can be used to develop interval velocity curves and customized to assess etiologic determinants such as genetic and physiological factors.

Selective transcriptions are coupled with proteosynthesis, nonselective with cell division. Growth means increase in size due to an increase of existing structural and functional units. Differentiation is a process whereby a relatively simple system is changed into a more complicated one.

Human Fetal Growth and Development

The start of pregnancy is actually the first day of your last menstrual period. This is called the gestational age, or menstrual age. Your healthcare provider will ask you about this date and will use it to figure out how far along you are in your pregnancy.

Don't have an account? This chapter examines the sources of variation in fetal growth, in particular nutrition in the context of the fetal nutritional programming hypothesis. The influence of fetal and maternal genotype on fetal growth is considered and set in the context of non-genetic intergenerational influences on birthweight, such as the mother's height and her own birthweight. The concept of programming is considered both with reference to nutritional programming and the wider view of programming, with particular reference to the hormonal, metabolic, and circulatory milieu to which the fetus is exposed. Oxford Scholarship Online requires a subscription or purchase to access the full text of books within the service.

This is called her background risk. This fact sheet talks about the critical periods of development and types of birth defects that can result from exposures at different stages of pregnancy. This information should not take the place of medical care and advice from your health care provider. During these times , the body can be very sensitive to damage caused by medications, alcohol or other harmful exposures. Yes, the risk depends on what body part is developing at the time of exposure.

This article is only available in the PDF format. Download the PDF to view the article, as well as its associated figures and tables. The book summarizes the proceedings of the meeting of the Society for the Study of Human Biology. The topic is timely, as many advances are being made in human fetal research with the advent of liberalized abortion laws. There are four main sections.

Intrauterine growth restriction IUGR , a condition that occurs due to various reasons, is an important cause of fetal and neonatal morbidity and mortality. It has been defined as a rate of fetal growth that is less than normal in light of the growth potential of that specific infant. Usually, IUGR and small for gestational age SGA are used interchangeably in literature, even though there exist minute differences between them.

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