出典(authority):フリー百科事典『ウィキペディア(Wikipedia)』「2016/04/08 14:51:00」(JST)
Stillbirth | |
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Ultrasonography is often used to diagnose stillbirth or medical conditions that raise the risk of stillbirth.
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Classification and external resources | |
Specialty | Obstetrics |
ICD-10 | P95 |
OMIM | 614389 |
DiseasesDB | 6890 |
MedlinePlus | 002304 |
eMedicine | topic list |
MeSH | D050497 |
[edit on Wikidata]
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Stillbirth is often defined as fetal death after 20 weeks of gestation,[1] but a fetus greater than any combination of 16, 20, 22, 24, or 28 weeks gestational age and 350g, 400g, 500g, or 1000g birth weight may be considered stillborn depending on local law.[2] Once the fetus has died, the mother may or may not have contractions and undergo childbirth or in some cases, a Caesarean section. Most stillbirths occur in full-term pregnancies. The cause is often unknown.[1]
In the U.S., the Born-Alive Infants Protection Act of 2002 specifies that any breathing, heartbeat, pulsating umbilical cord, or confirmed voluntary muscle movement indicate live birth rather than stillbirth.[3]
The term is often used in distinction to live birth (the baby was born alive, even if it died shortly thereafter) or miscarriage (early pregnancy loss). The word miscarriage is often used incorrectly to describe stillbirths.
The causes of a large percentage of human stillbirths remain unknown, even in cases where extensive testing and autopsy have been performed. A rarely used term to describe these is "sudden antenatal death syndrome" or SADS, a phrase coined by Cacciatore & Collins in 2000.[4] Many stillbirths occur at full term to apparently healthy mothers, and a postmortem evaluation reveals a cause of death in only about 40% of autopsied cases.[5]
In cases where the cause is known, some possibilities of the cause of death are:
After a stillbirth there is a 2.5% risk of another stillbirth in the next pregnancy (an increase from 0.4%).[9]
It is unknown how much time is needed for a fetus to die. Fetal behavior is consistent and a change in the fetus' movements or sleep-wake cycles can indicate fetal distress.[8] A decrease or cessation in sensations of fetal activity may be an indication of fetal distress or death, though it is not entirely uncommon for a healthy fetus to exhibit such changes, particularly near the end of a pregnancy when there is considerably less space in the uterus than earlier in pregnancy for the fetus to move about. Still, medical examination, including a nonstress test, is recommended in the event of any type of any change in the strength or frequency of fetal movement, especially a complete cease; most midwives and obstetricians recommend the use of a kick chart to assist in detecting any changes. Fetal distress or death can be confirmed or ruled out via fetoscopy/doptone, ultrasound, and/or electronic fetal monitoring. If the fetus is alive but inactive, extra attention will be given to the placenta and umbilical cord during ultrasound examination to ensure that there is no compromise of oxygen and nutrient delivery.
When the umbilical cord is constricted (q.v. "accidents" above), the fetus experiences periods of hypoxia, and may respond by unusually high periods of kicking or struggling, to free the umbilical cord. These are sporadic if constriction is due to a change in the fetus' or mother's position, and may become worse or more frequent as the fetus grows. Extra attention should be given if mothers experience large increases in kicking from previous childbirths, especially when increases correspond to position changes.[8]
Regulating High blood pressure, diabetes and drug use may reduce the risk of a stillbirth. Umbilical cord constriction may be identified and observed by ultrasound, if requested.
Some maternal factors are associated with stillbirth, including being age 40 or older, having diabetes, having a history of addiction to illegal drugs, being overweight or obese, and smoking cigarettes in the three months before getting pregnant.[10]
Fetal death in utero does not present an immediate health risk to the woman, and labour will usually begin spontaneously after two weeks, so the woman may choose to wait and bear the fetal remains vaginally. After two weeks, the woman is at risk of developing blood clotting problems, and labor induction is recommended at this point. In many cases, the woman will find the idea of carrying the dead fetus emotionally traumatizing and will elect to have labor induced. Caesarean birth is not recommended unless complications develop during vaginal birth. Women need to heal physically after a stillbirth just as they do emotionally. They will go through the healing process afterwards just as they would after a normal healthy birth.[11]
The average stillbirth rate in the United States is approximately 1 in 160 births, which is roughly 26,000 stillbirths each year.[12] In Australia,[13] England, Wales,[14][15] and Northern Ireland,[citation needed] the rate is approximately 1 in every 200 births; in Scotland, 1 in 167.[citation needed]
In developing countries, where medical care can be of low quality or unavailable, the stillbirth rate is much higher.
The way people view stillbirths has changed dramatically over time. Years ago, parents were expected to recover from the loss of a fetus just months after it happened. In the early 20th century, when a stillbirth occurred, the baby was taken and discarded and the parents were expected to immediately let go of the attachment and try for another baby.[16]
In Australia any stillborn weighing more than 400 grams, or more than 20 weeks in gestation, must have its birth registered.[17]
In Austria a stillbirth is defined as birth of a child of at least 500 g weight without vital signs, e.g. blood circulation, breath or muscle movements.
Beginning in 1959, "the definition of a stillbirth was revised to conform, in substance, to the definition of fetal death recommended by the World Health Organization."[18] The definition of "fetal death" promulgated by the World Health Organization in 1950 is as follows:
In Germany a stillbirth is defined as birth of a child of at least 500g weight without blood circulation or breath. Details for burial vary amongst the federal states.[20]
Since 1 Jan 1995 stillbirths occurring in the Republic of Ireland must be registered; stillbirths which occurred before that date can also be registered but evidence is required.[21] For the purposes of civil registration, s.1 of the Stillbirths Registration Act 1994 refers to :-
"...a child weighing at least 500 grammes, or having reached a gestational age of at least 24 weeks who shows no signs of life."
In the Netherlands, stillbirth is defined differently by the central bureau of statistics (CBS) and the Dutch perinatal registry (Stichting PRN). The birth and mortality numbers from the CBS include all liveborn children, regardless of gestational duration and all stillbirths from 24 weeks of gestation and onwards. In the Perinatal Registry, gestational duration of both liveborn and stillborn children is available. They register all liveborn and stillborn children from 22, 24 or 28 weeks of gestation and onwards (dependent on the report: fetal, neonatal or perinatal mortality). Therefore, data from these institutions on (still)births can not simply be compared one-on-one.
The registration of still-births has been required in England and Wales from 1927, in Scotland from 1939 but is not required in Northern Ireland.[22] Sometimes a pregnancy is terminated deliberately during a late phase, for example for congenital anomaly. UK law requires these procedures to be registered as "stillbirths".[23]
For the purposes of the Births and Deaths Registration Act 1926 (as amended), section 12 contains the definition that :-
"still-born" and "still-birth" shall apply to any child which has issued forth from its mother after the twenty fourth week of pregnancy and which did not at any time after being completely expelled from its mother, breathe or show any other signs of life.
A similar definition is applied within the Births and Deaths Registration Act 1953 (as amended), contained in s.41.
The above definitions apply within those Acts thus other legislation will not necessarily be in identical terms.
s.2 of the 1953 Act requires that registration of a birth takes place within 42 days of the birth except where an inquest takes place or the child has been "found exposed" in which latter case the time limit runs from the time of finding.
Extracts from the register of still-births are restricted to those who have obtained consent from the Registrar General for England and Wales.
Section 56(1) of the Registration of Births, Deaths and Marriages (Scotland) Act 1965 (as amended) contains the definition that :-
"still-born child" means a child which has issued forth from its mother after the twenty-fourth week of pregnancy and which did not at any time after being completely expelled from its mother breathe or show any other signs of life, and the expression "still-birth" shall be construed accordingly
s.21(1) of the same Act requires that :-
Except so far as otherwise provided by this section or as may be prescribed, the provisions of this Part of this Act shall, so far as applicable, apply to still-births in like manner as they apply to births of children born alive.
In the general case, s.14 of the Act requires that a birth has to be registered within 21 days of the birth or of the child being found.
Unlike the registers for births, marriages, civil partnerships and deaths, the register of still-births is not open to public access and issue of extracts requires the permission of the Registrar General for Scotland.
In Northern Ireland the Births and Deaths Registration (Northern Ireland) Order 1976,[24] as amended contains the definition :-
"still-birth" means the complete expulsion or extraction from its mother after the twenty-fourth week of pregnancy of a child which did not at any time after being completely expelled or extracted breathe or show any other evidence of life.
Registration of still-births can be made by a relative or certain other persons involved with the still-birth but it is not compulsory to do so. Registration takes place with the District Registrar for the Registration District where the still-birth occurred or for the District in which the mother is resident. A still-birth certificate will be issued to the registrant with further copies only available to those obtaining official consent for their issue. Registration may be made within three months of the still-birth[25]
In the United States, there is no standard definition of the term 'stillbirth'.[19] The Centers for Disease Control and Prevention collects statistical information on "live births, fetal deaths, and induced termination of pregnancy" from 57 reporting areas in the United States. Each reporting area has different guidelines and definitions for what is being reported; many do not use the term "stillbirth" at all. The federal guidelines suggests (at page 1) that fetal death and stillbirth can be interchangeable terms. The CDC definition of "fetal death" is based on the definition promulgated by the World Health Organization in 1950 (see section above on Canada). Researchers are learning more about the long term psychiatric sequelae of traumatic birth and believe the effects may be intergenerational[26]
The federal guidelines recommend reporting those fetal deaths whose birth weight is over 12.5 oz (350g), or those more than 20 weeks gestation. Forty-one areas use a definition very similar to the federal definition, thirteen areas use a shortened definition of fetal death, and three areas have no formal definition of fetal death. Only 11 areas specifically use the term 'stillbirth', often synonymously with late fetal death, however they are split between whether stillbirths are "irrespective of the duration of pregnancy", or whether some age or weight constraint is applied. A movement in the U.S. has changed the way that stillbirths are documented through vital records. Previously, only the deaths were reported. However 27 states have enacted legislation that offers some variation of a birth certificate as an option for parents who choose to pay for one. Parents may not claim a tax exemption for stillborn infants, even if a birth certificate is offered. To claim an exemption, the birth must be certified as live, even if the infant only lives for a very brief period.
There is probably no health outcome with a greater number of conflicting, authoritative, legally mandated definitions. The basic WHO definition of fetal death is the intrauterine death of any conceptus at any time during pregnancy. However, for practical purposes, legal definitions usually require recorded fetal deaths to attain some gestational age (16, 20, 22, 24, or 28 weeks) or birth weight (350, 400, 500, or 1000 g). In the US states, there are eight different definitions by combinations of gestational age and weight, and at least as many in Europe.
Stillbirths per 1,000 live births have increased from 5.1 in 2010 to 5.2 in 2011
Stillbirth is defined within Australia as fetal death (no signs of life), whether antepartum or intrapartum, at ≥20 weeks of gestation or ≥400 g birthweight, if gestational age is unknown.
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