Gastroschisis refers to a (full thickness) defect in the abdominal wall, adjacent to the umbilical cord insertion, through which extrusion of the fetal bowel has occurred. The defect usually arises to the right of the umbilicus and is generally small (less than 2 cm). It is most commonly found on the right side of the umbilical cord.
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Etiology
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Gastroschisis occurs in about 1 in 5 -10,000 live births. It appears to occur more frequently in women who are less than 20 years of age. It may also be more common in women who smoke and use drugs such as cocaine.
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During the 4th to 5th week of embryonic development the embryo, which has been a flat disk, folds in four directions: up and down and right and left sides. Each fold converges at the site of the umbilicus with the side folds forming the sides of the abdominal wall.
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Gastroschisis is thought to occur because of interruptions to the blood supply or blood vessels which supply the muscles of the abdominal wall during the period of abdominal wall development.
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Diagnosis
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The fetal abdominal wall can be seen by ultrasound from 9 postmenstrual weeks although the defect cannot not been confidently diagnosed until after the 12th week of pregnancy.
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The ultrasound appearance of gastroschisis is of a normally positioned umbilical cord with a mass of bowel, which lacks a membrane cover, to the right of it. The bowel outside the abdominal cavity may be small or large bowel and occasionally also the stomach and has the appearance of a cauliflower.
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Late in pregnancy, the externalized bowel often appears thickened, matted, and mildly dilated due to chronic exposure to amniotic fluid. Both the bowel which remains inside the fetal abdomen and the external bowel may become dilated during the pregnancy.
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Ultrasound image of fetus with gastroschisis
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Photo: Gastroschisis: appearance of exteriorized bowel after birth
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Associations
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Gastroschisis is not usually associated with other fetal developmental abnormalities, however approximately 25% of babies will develop additional bowel problems (e.g. stenosis, atresia [constrictions], malrotation).
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Data collected in Australia would suggest that about 1.8% of fetuses with a gastroschisis will also have a chromosomal abnormality. These are usually chromosomal rearrangements rather than the more usual trisomies.
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Other associated abnormalities include extrophy of the urinary bladder, fetal growth restriction, and minor cardiac anomalies (2-5%).
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Oligohydramnios (reduced amniotic fluid) may occur with gastroschisis.
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The overall survival of babies with gastroschisis is over 90%.
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Antenatal care / monitoring
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All women referred to the Royal Women's Hospital with a fetus with gastroschisis will have their pregnancy managed through the Fetal Management Unit. They will be seen by an Obstetrician at each visit and will meet a Paediatrician and a Paediatric Surgeon at least once.
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As there is a small risk of a chromosomal abnormality (and because other defects cannot be always excluded) we offer all women who have a fetus with a gastroschisis an amniocentesis (link) to check the karyotype.
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Women will attend the clinic for their usual antenatal visits however in addition will require serial ultrasounds (every 4 weeks) to check fetal growth and amniotic fluid volumes. If either the growth or amniotic fluid volume is abnormal the scans may be performed more frequently. Most women will have additional surveillance with ultrasound biophysical tests and or cardiotocographs (CTG) during the third trimester.
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About 30% of women will labour prematurely (before 37 weeks gestation).
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Intrapartum care
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To optimise neonatal care a fetus with gastroschisis is best delivered at a tertiary level centre. We therefore advise that all women referred to our unit are delivered at the Royal Women's Hospital.
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If the pregnancy has progressed otherwise normally and without complication it is usual to wait for the spontaneous onset of labour (whilst continuing the antenatal monitoring) until the "due date" after which delivery is arranged.
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There is no evidence that mode of delivery effects neonatal outcome therefore a fetus with gastroschisis is delivered by vaginal route unless there are other obstetric indications for caesarean delivery. There is, however, a higher rate of caesarean delivery in the presence of gastroschisis secondary to an increased incidence of nonreassuring fetal CTG monitoring in labour and the presence of meconium stained liquor.
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A paediatrician is present at the delivery.
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Neonatal care and management (including surgical)
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Most babies will not need vigorous resuscitation at birth.
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- It is of vital importance to emphasise the need to position the baby and support the exteriorised bowel in such a way as to maintain best possible circulation to the bowel by taking tension off the mesenteric vessels; this is usually by having the baby in the right lateral posture with support under the bowel.
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- The exposed bowel is wrapped in cling wrap and the baby is wrapped and transferred to the Royal Women's Hospital neonatal intensive care unit to be stabilised.
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- Wet gauze must not be used against the bowel.
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Once the baby has been stabilised, arrangements will be made to transfer the baby to the Royal Children's Hospital Neonatal Intensive Care Unit for surgical assessment. The surgeons like to operate soon after transfer to get the exposed bowel covered. This protects the bowel and decreases the risk of infection. On many occasions this operation is straight-forward with the exposed bowel returned to the abdominal cavity and the skin closed. However this is not always possible as the abdominal cavity may be too small to accommodate comfortably all the exposed bowel. On these occasions a synthetic material is placed over the bowel and stitched to the abdomen. This is often referred to as a "silo". The silo is then gradually tightened over 7 - 10 days to slowly push the exposed bowel back into the abdominal cavity. Once the bowel is in the cavity the silo is removed and skin closed.
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Some babies with gastroschisis have very damaged bowel when they are born. Sometimes they can have blockages in the bowel. If these blockages have been present for a long time, they can cause parts of the bowel to be greatly distended. Even when these blockages are relieved after birth it can sometimes take many months for the bowel to function normally. What this means is that it can take many months for the baby to tolerate milk. They have a long stay in hospital and require intravenous feeding. Fortunately most babies do not have these types of problems and we find that feeding can be established within 7 - 21 days of age. Most babies with gastroschisis are discharged within 3-4 weeks of birth.
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Future
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Most women will not have another fetus with gastroschisis although there is a 3 - 5% reported recurrence risk.
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Royal Women's Hospital Clinical Practice Guidelines (CPGs) are intended to provide guidance to health care professionals, based on a thorough evaluation of research evidence, on the practical assessment and management of specific clinical issues or situations. The guidelines allow some flexibility on the part of the health care professional based on the needs of the specific patient for whom they are caring.
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