Prenatal development
Prenatal development (from
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
Terminology
In the human:
Different terms are used to describe prenatal development, meaning development before birth. A term with the same meaning is the "antepartum" (from Latin ante "before" and parere "to give birth") Sometimes "antepartum" is however used to denote the period between the 24th/26th week of
The perinatal period (from Greek peri, "about, around" and Latin nasci "to be born") is "around the time of
Fertilization
Fertilization marks the first
The zygote will develop into a male if the egg is fertilized by a sperm that carries a
Development of the embryo
Following fertilization, the embryonic stage of development continues until the end of the 10th week (
The
The
Rapid growth occurs and the embryo's main features begin to take form. This process is called
- fetal alcohol syndrome
- Infection (such as rubella or cytomegalovirus)
- Radiation from x-rays or radiation therapy
- Nutritional deficiencies such as lack of folate which contributes to spina bifida
Nutrition
The embryo passes through 3 phases of acquisition of nutrition from the mother:[9]
- Absorption phase: Zygote is nourished by cellular cytoplasm and secretions in fallopian tubes and uterine cavity.[10]
- Histoplasmic transfer: After trophoblasts.
- Hematotrophic phase: After third week of gestation, substances are transported passively via intervillous space.
Development of the fetus
The first ten weeks of
From the 10th week of gestation (8th week of development), the developing embryo is called a fetus. All major structures are formed by this time, but they continue to grow and develop. 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 of organ systems
This article is part of a series on the |
Development of organ systems |
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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.
Fetal blood
Red blood cells
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.
White blood cells
The fetus starts producing
Glands
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.
Cognitive development
Electrical
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
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.[19] Also, most low-frequency sounds (less than 300 Hz) can reach the fetal inner ear in the womb of mammals.[20] Those low-frequency sounds include pitch, rhythm, and phonetic information related to language.[21] Studies have indicated that fetuses react to and recognize differences between sounds.[22] Such ideas are further reinforced by the fact that newborns present a preference for their mother's voice,[23] present behavioral recognition of stories only heard during gestation,[24] and (in monolingual mothers) present preference for their native language.[25] A more recent study with EEG demonstrated different brain activation in newborns hearing their native language compared to when they were presented with a different language, further supporting the idea that language learning starts while in gestation.[26]
Growth rate
The growth rate of a fetus is linear up to 37 weeks of gestation, after which it plateaus.[9] The growth rate of an embryo and infant can be reflected as the weight per gestational age, and is often given as the weight put in relation to what would be expected by the gestational age. 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, while 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 2000 grams) can slightly increase the likelihood of schizophrenia.[27]
The growth rate can be roughly correlated with the fundal height of the uterus which can be estimated by abdominal palpation. More exact measurements can be performed with obstetric ultrasonography.
Factors influencing development
Poverty
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. Many of these expecting mothers have little education and are therefore less aware of the risks of
Mother's age
Women between the ages of 16 and 35 have a healthier environment for a fetus than women under 16 or over 35.[29] Women between this age gap are more likely to have fewer complications. 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.[30] Premature babies from young mothers are more likely to have neurological defects that will influence their coping capabilities – irritability, trouble sleeping, constant crying for example. There is an increased 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.
Drug use
An estimated 5 percent of fetuses in the United States are exposed to illicit drug use during pregnancy.[31] Maternal drug use occurs when drugs ingested by the pregnant woman are metabolized in the placenta and then transmitted to the fetus. Recent research displays 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.[32]
Cannabis
When using
Opioids
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.[36]
Cocaine
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. The vasoconstriction of the effects of cocaine lead to a decrease in placental blood flow to the fetus that results in fetal hypoxia (oxygen deficiency) and decreased fetal nutrition; these vasoconstrictive effects on the placenta have been linked to the number of complications in malformations that are evident in the newborn. [37]
Methamphetamine
Prenatal methamphetamine exposure has shown to negatively impact brain development and behavioral functioning. A 2019 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.[38]
Alcohol
Maternal alcohol use leads to disruptions of the fetus' brain development, interferes with the fetus' 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.[39] Fetal alcohol spectrum disorder is a developmental disorder that is a consequence of heavy alcohol intake by the mother during pregnancy. Children with FASD have a variety of distinctive facial features, heart problems, and cognitive problems such as developmental disabilities, attention difficulties, and memory deficits.[39]
Tobacco use
Tobacco smoking during pregnancy exposes the fetus to nicotine, tar, and carbon monoxide. Nicotine results in less blood flow to the fetus because it constricts the blood vessels. Carbon monoxide reduces the oxygen flow to the fetus. The reduction of blood and oxygen flow may result in miscarriage, stillbirth, low birth weight, and premature births.[40] Exposure to secondhand smoke leads to higher risks of low birth weight and childhood cancer.[41]
Infections
If a mother is
Maternal nutrition
Adequate nutrition is needed for a healthy fetus. Mothers who gain less than 20 pounds during pregnancy are at increased risk for having a preterm or low birth weight infant.
Low birth weight
Low birth weight increases an infants risk of long-term growth and cognitive and language deficits. It also results in a shortened gestational period and can lead to prenatal complications.
Stress
Environmental toxins
Exposure to
See also
- Prenatal memory
- Prenatal and perinatal psychology
- Fetal pig
- Timeline of human prenatal development
- Transplacental carcinogenesis
References
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Further reading
- MedlinePlus Encyclopedia: Fetal development
- Moore, Keith L. (1998). The Developing Human (3rd ed.). Philadelphia PA: W.B. Saunders Company. ISBN 9780721669748.
- Wilcox AJ, Baird DD, PMID 10362823.
- Ljunger E, Cnattingius S, Lundin C, Annerén G (November 2005). "Chromosomal anomalies in first-trimester miscarriages". Acta Obstet Gynecol Scand. 84 (11): 1103–7. S2CID 40039636.
- Newman, Barbara; Newman, Philip (10 March 2008). "The Period of Pregnancy and Prenatal Development". Development Through Life: A Psychosocial Approach. Cengage Learning. ISBN 978-0-495-55341-0.
- "Prenatal Development – Prenatal Environmental Influences – Mother, Birth, Fetus, and Pregnancy." Social Issues Reference. Version Child Development Vol. 6. N.p., n.d. Web. 19 Nov. 2012.
- Niedziocha, Laura. "The Effects of Drugs And Alcohol on Fetal Development | LIVESTRONG.COM." LIVESTRONG.COM – Lose Weight & Get Fit with Diet, Nutrition & Fitness Tools | LIVESTRONG.COM. N.p., 4 Sept. 2011. Web. 19 Nov. 2012. <How To Adult>.
- Jaakkola, JJ; Gissler, M (January 2004). "Maternal smoking in pregnancy, fetal development, and childhood asthma". American Journal of Public Health. 94 (1): 136–40. PMID 14713711.
- Gutbrod, T (1 May 2000). "Effects of gestation and birth weight on the growth and development of very low birthweight small for gestational age infants: a matched group comparison". Archives of Disease in Childhood: Fetal and Neonatal Edition. 82 (3): 208F–214. PMID 10794788.
- Brady, Joanne P., Marc Posner, and Cynthia Lang. "Risk and Reality: The Implications of Prenatal Exposure to Alcohol and Other Drugs ." ASPE. N.p., n.d. Web. 19 Nov. 2012. <Risk and Reality: The Implications of Prenatal Exposure to Alcohol and Other Drugs>.
External links
- Chart of human fetal development, U.S. National Library of Medicine (NLM)
- U.K. Human Fertilisation and Embryology Authority (HFEA), regulatory agency overseeing the use of gametes and embryos in fertility treatment and research
- "Child Safety tips: 10 Expert Tips for Keeping Your Kids Safe",