Factors within labour are complex but processes such as uteroplacental vascular disease, reduced uterine perfusion, fetal sepsis, reduced fetal reserves and cord compression can be involved alone or in combination. Gestational and antepartum factors can modify the fetal response to them.
Reduced liquor volume, maternal hypovolaemia and fetal growth restriction are known associations.
The overall risk of fetal distress (defined as need for prompt caesarean delivery) was shown to be 3.1% in an unselected population. The risk exceeded 20% in patients with severe pre-eclampsia, post-term or fetal growth-restricted fetuses with abnormal Doppler studies, moderate/severe asthma and severe hypothyroidism.
Women with a history of:
- Intrauterine growth restriction.
- Oligohydramnios or polyhydramnios.
- Multiple pregnancy.
- Rhesus sensitisation.
- Diabetes and other chronic diseases.
- Decreased fetal movements.
- Post-term pregnancy.
- Intrauterine growth restriction.
- Raised vascular resistance (measured in the umbilical artery, by ultrasound).
- Fetal hypoxia or acidosis (on fetal blood sampling during labour).
- Non-stress test - monitors fetal heart rate acceleration following fetal movement. A non-reactive result suggests fetal distress requiring further assessment.
- Contraction stress test - measures response of fetal heart rate to spontaneous or nipple/oxytocin-stimulated contraction. Late decelerations suggest fetal distress.
- Biophysical profile - measures fetal breathing and gross body movements, fetal tone and heart rate acceleration and amniotic fluid volume to develop a score.
- Continuous fetal heart rate monitoring - uses an electrode attached to the fetal scalp or a detector on the mother's abdomen:
- Normal range at term is 110-160 bpm.
- Fetal bradycardia (<110 bpm) or tachycardia (>160 bpm) may be associated with hypoxia but several other factors can cause tachycardia - eg, maternal pyrexia or dehydration.
- Late decelerations - defined as uniform, repeated, periodic slowing of the fetal heart rate, whose onset is from mid to end of the contraction, with its nadir more than 20 seconds after the peak intensity of the contraction - suggest fetal hypoxia.
- Fetal scalp blood monitoring:
- pH >7.25 - repeat if cardiotocography (CTG) continues to deteriorate.
- pH 7.21-7.24 - repeat in 30 minutes.
- pH <7.20 - urgent delivery is required.
Delivery within 30 minutes has become the standard for audit purposes, but it is rarely achieved and its clinical significance has been called to question.
See also the Intrapartum Fetal Monitoring article.
There have been no recent trials of operative versus conservative management of suspected fetal distress.
- Signs of fetal distress require monitoring with a view to induction of labour.
- Continuing fetal distress during labour may indicate the need for caesarean section.
- Term or post-mature fetuses may produce meconium-stained liquor. This can be detrimental to the fetal lungs by producing a chemical pneumonitis if inhaled.
- Amnio-infusion has been shown to be beneficial in this situation, with a reduced risk of caesarean section:
- This is an initial infusion of a 250-500 ml bolus of warmed normal saline, through a double lumen intrauterine pressure catheter. (Uterine pressure and fetal heart rate - via scalp electrode - are monitored constantly.) It is thought to dilute meconium and reduce the risk of meconium aspiration. It is not, however recommended by the National Institute for Health and Clinical Excellence (NICE).
- The potential adverse effects include umbilical cord prolapse, uterine scar rupture and amniotic fluid embolism.
- It has also been used in pregnancies complicated by oligohydramnios, with similar positive outcomes.
Further reading & references
- Chauhan SP, Magann EF, Scott JR, et al; Cesarean delivery for fetal distress: rate and risk factors.; Obstet Gynecol Surv. 2003 May;58(5):337-50.
- Graham EM, Ruis KA, Hartman AL, et al; A systematic review of the role of intrapartum hypoxia-ischemia in the causation of neonatal encephalopathy. Am J Obstet Gynecol. 2008 Dec;199(6):587-95. doi: 10.1016/j.ajog.2008.06.094.
- Canterino JC, Ananth CV, Smulian J, et al; Maternal age and risk of fetal death in singleton gestations: USA, 1995-2000.; J Matern Fetal Neonatal Med. 2004 Mar;15(3):193-7.
- Miller DA; Is advanced maternal age an independent risk factor for uteroplacental insufficiency?; Am J Obstet Gynecol. 2005 Jun;192(6):1974-80; discussion 1980-2.
- Intrapartum care, NICE Clinical Guideline (2007)
- Schauberger CW, Chauhan SP; Emergency cesarean section and the 30-minute rule: definitions. Am J Perinatol. 2009 Mar;26(3):221-6. doi: 10.1055/s-0028-1103033. Epub 2008 Nov 21.
- Hofmeyr GJ, Kulier R; Operative versus conservative management for 'fetal distress' in labour. Cochrane Database Syst Rev. 2012 Jun 13;6:CD001065. doi: 10.1002/14651858.CD001065.pub2.
- Hendrix NW, Chauhan SP; Cesarean delivery for nonreassuring fetal heart rate tracing.; Obstet Gynecol Clin North Am. 2005 Jun;32(2):273-86, ix.
- Hofmeyr GJ, Lawrie TA; Amnioinfusion for potential or suspected umbilical cord compression in labour. Cochrane Database Syst Rev. 2012 Jan 18;1:CD000013. doi: 10.1002/14651858.CD000013.pub2.
- Abdel-Aleem H, Amin AF, Shokry M, et al; Therapeutic amnioinfusion for intrapartum fetal distress using a pediatric feeding tube.; Int J Gynaecol Obstet. 2005 Aug;90(2):94-8.
|Original Author: Dr Hayley Willacy||Current Version: Dr Colin Tidy||Peer Reviewer: Dr John Cox|
|Last Checked: 11/02/2013||Document ID: 1342 Version: 24||© EMIS|
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