Gestational age: Difference between revisions
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In [[obstetrics]], '''gestational age''' can mean either '''LMP gestational age''' or '''CE gestational age.''' LMP gestational age is considered to be the age of an [[embryo]] or [[fetus]] (or newborn infant) counted from the first day of the woman's last menstrual period (LMP). CE gestational age is an estimate of LMP gestational age which is based on health status indicators (Clinical Estimate).<ref name="nih">{{cite web |url=http://www.nlm.nih.gov/medlineplus/ency/article/002367.htm |title= MedlinePlus Medical Encyclopedia: Gestational age |accessdate= 2007-01-28 |editor= John Goldenring |date=November 2004 |publisher= A.D.A.M., Inc.}} (distinguishing between "calendar gestational age" and "developmental gestational age").</ref><ref>[http://dx.doi.org/10.1016/j.annepidem.2007.01.035 Comparison of Gestational Age Classifications: Date of Last Menstrual Period vs. Clinical Estimate], Annals of Epidemiology, Volume 17, Issue 6, Pages 425-430. M. Wingate, G. Alexander, P. Buekens, A. Vahratian</ref><ref>Anika Rahman, Laura Katzive and Stanley K. Henshaw. [http://www.guttmacher.org/pubs/journals/2405698.pdf A Global Review of Laws on Induced Abortion, 1985-1997], International Family Planning Perspectives (Volume 24, Number 2, June 1998): there is "no uniform method of calculating gestational age."</ref><ref>[http://cancerweb.ncl.ac.uk/cgi-bin/omd?gestational+age On-Line Medical Dictionary] (British)</ref> |
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In [[embryology]], '''gestational age''' is synonymous with the '''fertilization age''' (also called '''conceptional age''' or '''developmental age''') of an embryo or fetus.<ref>[http://activate.lww.com/semdweb/internetsomd/ASP/1487087.asp Stedman's Online Medical Dictionary, 27th Edition]</ref><ref>[http://dictionary.reference.com/search?q=gestational+age&r=66 dictionary.com]</ref><ref>[http://lookwayup.com/lwu.exe/definition;gestationa%20age Look Way Up dictionary]</ref> |
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| ⚫ | The fertilization age is always counted from fertilization, and the LMP gestational age is usually greater by about two weeks. This standard system of counting the progression of pregnancy starts approximately two weeks before fertilization takes place; it does not in itself constitute the beginning of [[pregnancy]].<ref name="cfn">{{cite journal |author=Engle W, American Academy of Pediatrics Committee on Fetus and Newborn |title=Age terminology during the perinatal period |journal=Pediatrics |volume=114 |issue=5 |pages=1362-4 |year=2004 |id=PMID 15520122 |url=http://aappolicy.aappublications.org/cgi/content/full/pediatrics;114/5/1362 |accessdate=2007-01-28}}</ref> |
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There is some [[Beginning of pregnancy controversy|controversy over the beginning of pregnancy]], and alternative counting systems have been suggested.<ref name="cfn" /> |
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| ⚫ | A full-term human pregnancy is considered to be 40 weeks (280 days) LMP gestational age, though pregnancy lengths between 38 and 42 weeks are considered normal. A fetus born prior to the 37th week of gestation is considered premature and faces increased risk of [[morbidity]] and [[death|mortality]]. |
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The events of [[prenatal development]] usually occur at known gestational ages. The gestational timing of a toxin exposure or infection can be used to predict the potential consequences to the fetus. |
The events of [[prenatal development]] usually occur at known gestational ages. The gestational timing of a toxin exposure or infection can be used to predict the potential consequences to the fetus. |
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Calculations of gestational age from LMP are sometimes incorrect due to normal |
Calculations of gestational age from LMP are sometimes incorrect due to normal variation from the average ovulation date. The gestational age of an individual infant can be more accurately estimated from: |
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# The [[mother]]'s knowledge of the date of [[sexual intercourse]]. |
# The [[mother]]'s knowledge of the date of [[sexual intercourse]]. |
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# The mother's knowledge of fertility signs related to [[ovulation]]. The needed observations are normally made by mothers who use [[fertility awareness]] methods to get pregnant. |
# The mother's knowledge of fertility signs related to [[ovulation]]. The needed observations are normally made by mothers who use [[fertility awareness]] methods to get pregnant. |
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Revision as of 17:29, 15 March 2008
In obstetrics, gestational age can mean either LMP gestational age or CE gestational age. LMP gestational age is considered to be the age of an embryo or fetus (or newborn infant) counted from the first day of the woman's last menstrual period (LMP). CE gestational age is an estimate of LMP gestational age which is based on health status indicators (Clinical Estimate).[1][2][3][4]
In embryology, gestational age is synonymous with the fertilization age (also called conceptional age or developmental age) of an embryo or fetus.[5][6][7]
The fertilization age is always counted from fertilization, and the LMP gestational age is usually greater by about two weeks. This standard system of counting the progression of pregnancy starts approximately two weeks before fertilization takes place; it does not in itself constitute the beginning of pregnancy.[8]
There is some controversy over the beginning of pregnancy, and alternative counting systems have been suggested.[8]
A full-term human pregnancy is considered to be 40 weeks (280 days) LMP gestational age, though pregnancy lengths between 38 and 42 weeks are considered normal. A fetus born prior to the 37th week of gestation is considered premature and faces increased risk of morbidity and mortality.
The events of prenatal development usually occur at known gestational ages. The gestational timing of a toxin exposure or infection can be used to predict the potential consequences to the fetus.
Calculations of gestational age from LMP are sometimes incorrect due to normal variation from the average ovulation date. The gestational age of an individual infant can be more accurately estimated from:
- The mother's knowledge of the date of sexual intercourse.
- The mother's knowledge of fertility signs related to ovulation. The needed observations are normally made by mothers who use fertility awareness methods to get pregnant.
- Examination of the newborn infant. In the twentieth century, doctors (especially pediatricians) were trained to recognize the physical changes occurring to the fetus in the latter half of pregnancy so that a maturational age could be estimated.
- An obstetric ultrasound ("dating scan", in the UK routinely offered around 12 weeks) during the pregnancy, whereby sizes of certain fetal body parts are measured.
The fertilization age of children conceived by in vitro fertilization is known to the hour.
See also
References
- ^ John Goldenring, ed. (November 2004). "MedlinePlus Medical Encyclopedia: Gestational age". A.D.A.M., Inc. Retrieved 2007-01-28. (distinguishing between "calendar gestational age" and "developmental gestational age").
- ^ Comparison of Gestational Age Classifications: Date of Last Menstrual Period vs. Clinical Estimate, Annals of Epidemiology, Volume 17, Issue 6, Pages 425-430. M. Wingate, G. Alexander, P. Buekens, A. Vahratian
- ^ Anika Rahman, Laura Katzive and Stanley K. Henshaw. A Global Review of Laws on Induced Abortion, 1985-1997, International Family Planning Perspectives (Volume 24, Number 2, June 1998): there is "no uniform method of calculating gestational age."
- ^ On-Line Medical Dictionary (British)
- ^ Stedman's Online Medical Dictionary, 27th Edition
- ^ dictionary.com
- ^ Look Way Up dictionary
- ^ a b Engle W, American Academy of Pediatrics Committee on Fetus and Newborn (2004). "Age terminology during the perinatal period". Pediatrics. 114 (5): 1362–4. PMID 15520122. Retrieved 2007-01-28.