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Synonym: fetal compromise; non-reassuring fetal heart rate trace
Fetal distress refers to the compromise of the fetus due to inadequate oxygen or nutrient supply. This can occur due to maternal, fetal or placental factors. At its most severe it may lead to neonatal brain injury or stillbirth. Its presence may be suspected due to various factors but all have a high false positive rate.
The main cause of antepartum fetal distress is uteroplacental insufficiency.
Factors within labour are complex but processes such as uteroplacental vascular disease, reduced uterine perfusion, intrauterine 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 prompt caesarean delivery needed for fetal concern 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 and also in women with moderate/severe asthma or severe hypothyroidism.
The vast majority of cases of cerebral palsy in otherwise normal term infants are not associated with intrapartum hypoxia-ischaemia.
Includes women with a history of:
- Intrauterine growth restriction (IUGR).
- Oligohydramnios or polyhydramnios.
- Multiple pregnancy.
- Rhesus sensitisation.
- Diabetes and other chronic diseases.
- Pre-eclampsia or pregnancy-induced hypertension.
- Decreased fetal movements.
- Recurrent antepartum haemorrhage.
- Post-term pregnancy.
Maternal age over 35 years, and particularly over 40, is an independent risk factor for uteroplacental insufficiency, fetal distress and stillbirth; the highest risk is in older women who are also nulliparous[3, 4].
See also separate Intrapartum Fetal Monitoring article.
Fetal distress presents in varied ways and to differing degrees. It may be suspected by the following, which may also be used for further evaluation of suspected fetal distress:
- Clinical suspicion when decreased fetal movements are felt by the mother or there is a slowing or stopping of the growth of serial symphysis fundal height.
- Abnormal sonographic biometric parameters when IUGR or macrosomia is suspected.
- Doppler ultrasound is particularly valuable when performed up to 34 weeks of gestation:
- Umbilical artery Doppler may detect changes that reflect increasing placental vascular resistance.
- Fetal arterial Doppler of, for example, the middle cerebral artery, may detect reduced resistance which has developed to maintain blood flow to the fetal brain when placental function is impaired.
- Fetal venous Doppler may detect changes indicative of impaired cardiac function and fetal acidosis.
- Cardiotocography (CTG) shows the fetal heart rate response to fetal movement and to maternal contractions. The trace it produces may be described as reassuring, non-reassuring or abnormal:
- Antenatal CTG:
- A normal fetal heart rate accelerates with fetal movement and is described as reactive.
- Stillbirth rates have been shown to be significantly lower after a reactive trace than after a non-reactive trace.
- CTG interpretation is open to inter- and intra-observer variation but can be interpreted by computerised analysis. CTG should not be used as the only form of surveillance of a high-risk pregnancy.
- A contraction stress test, carried out during induced contractions using oxytocin, has no clinical benefits, a false positive rate as high as 50% and may have significant adverse effects. It is not used in the UK.
- Intrapartum CTG:
- Biophysical profile (BPP) is time-consuming and rarely abnormal in the presence of normal umbilical arterial Doppler. It consists of a combination of CTG, fetal behaviour (including movement, tone and breathing) and amniotic fluid volume. This produces a BPP score to predict the degree of any compromise to the fetus. Available evidence does not support its routine use in high-risk pregnancies but observational data suggest it has good negative predictive value for fetal compromise.
- Amniotic fluid volume, both oligohydramnios and polyhydramnios, has been shown to be associated with poor fetal outcomes. However, oligohydramnios is itself associated with IUGR and urogenital malformations, which were not controlled for in the studies demonstrating an association with poor outcomes. Polyhydramnios, when clinically apparent, is related to poor neonatal outcomes but mild, idiopathic polyhydramnios, detected only on ultrasound, is not associated with adverse outcomes.
- Fetal scalp blood sampling during labour, to measure lactate (in preference to pH if available), may be indicated for an abnormal intrapartum CTG. See separate Intrapartum Fetal Monitoring article for details.
A composite risk score, based on fetal Doppler flow resistance indices, has shown promise in identifying those fetuses antenatally who develop fetal distress intrapartum.
There have been no recent trials of operative versus conservative management of suspected fetal distress.
- Signs of antenatal fetal distress require monitoring with a view to induction of labour or planned caesarean section.
- Immediate delivery of a preterm fetus with suspected fetal distress may reduce the risk of intrauterine hypoxia but increases the risks associated with prematurity. Benefit may be gained by deferring delivery, especially if there is uncertainty; however, evidence is lacking to guide this decision.
- Continuing fetal distress during labour may indicate the need for delivery to be expedited:
- Speed of delivery should take into account the severity of fetal heart rate and blood sampling abnormalities and relevant maternal factors.
- The current accepted standard is that expedited delivery should occur as quickly and safely as possible and within 30 minutes if there is an immediate threat to life of either the mother or the fetus. However, this is not achieved in a substantial proportion of cases, although it is uncertain how significant this is clinically.
- There is some evidence that very short 'decision-to-incision' time (<20 minutes) may be inversely proportional to neonatal outcomes, ie lower umbilical pH and Apgar scores.
- Amnioinfusion has been shown to be beneficial in suspected umbilical cord compression (particularly when there is oligohydramnios), with a reduced risk of caesarean section:
- In this process, sodium chloride or Ringer's lactate is infused transcervically or, if the membranes are still intact, via a needle inserted under ultrasound guidance through the uterine wall.
- The potential adverse effects include umbilical cord prolapse, uterine scar rupture and amniotic fluid embolism.
- The current evidence on the safety and efficacy of this procedure means it is not recommended in the UK for intrauterine fetal resuscitation; it is only undertaken under special arrangements that include audit and research.
- Term or post-mature fetuses may produce meconium-stained liquor. Meconium can be detrimental to the fetal lungs by producing a chemical pneumonitis if inhaled:
- Significant meconium is defined as dark green or black amniotic fluid that is thick or tenacious, or any meconium-stained amniotic fluid containing lumps of meconium:
- If significant meconium is present, fetal blood sampling and advanced neonatal life support may be required at delivery.
- If there has been non-significant meconium, the baby should be observed at one and two hours.
- Amnioinfusion has been used to reduce the risk of meconium aspiration by diluting the meconium present; however, it is unclear whether this is beneficial and it is not used in routine practice.
Further reading and references
; Cesarean delivery for fetal distress: rate and risk factors. Obstet Gynecol Surv. 2003 May58(5):337-50.
; Cerebral palsy: causes, pathways, and the role of genetic variants. Am J Obstet Gynecol. 2015 May 21. pii: S0002-9378(15)00510-4. doi: 10.1016/j.ajog.2015.05.034.
; Risk factors for antepartum stillbirth and the influence of maternal age in New South Wales Australia: a population based study. BMC Pregnancy Childbirth. 2013 Jan 1613:12. doi: 10.1186/1471-2393-13-12.
; Royal College of Obstetricians and Gynaecologists, 15 June 2009
; Planned early delivery versus expectant management of the term suspected compromised baby for improving outcomes. Cochrane Database Syst Rev. 2015 Nov 24(11):CD009433. doi: 10.1002/14651858.CD009433.pub2.
; Royal College of Obstetricians and Gynaecologists (February 2011)
; Royal College of Obstetricians and Gynaecologists Green-top guideline (Mar 2013)
; Geburtshilfe Frauenheilkd. 2014 Aug74(8):721-732.
; NICE Quality Standard, December 2015
; NICE Clinical Guideline (Dec 2014)
; Prediction of fetal compromise in labor. Obstet Gynecol. 2014 Jun123(6):1263-71. doi: 10.1097/AOG.0000000000000292.
; Operative versus conservative management for 'fetal distress' in labour. Cochrane Database Syst Rev. 2012 Jun 136:CD001065. doi: 10.1002/14651858.CD001065.pub2.
; Immediate versus deferred delivery of the preterm baby with suspected fetal compromise for improving outcomes. Cochrane Database Syst Rev. 2016 Jul 127:CD008968. doi: 10.1002/14651858.CD008968.pub3.
; NICE Clinical Guideline (November 2011)
; Decision-to-incision time and neonatal outcomes: a systematic review and meta-analysis. Obstet Gynecol. 2014 Mar123(3):536-48. doi: 10.1097/AOG.0000000000000132.
; Crash emergency cesarean section: decision-to-delivery interval under 30 min and its effect on Apgar and umbilical artery pH. Arch Gynecol Obstet. 2005 Dec273(3):161-5. Epub 2005 Jul 26.
; Amnioinfusion for potential or suspected umbilical cord compression in labour. Cochrane Database Syst Rev. 2012 Jan 181:CD000013. doi: 10.1002/14651858.CD000013.pub2.
; NICE Interventional Procedure Guidance, November 2006
; Amnioinfusion for meconium-stained liquor in labour. Cochrane Database Syst Rev. 2014 Jan 23(1):CD000014. doi: 10.1002/14651858.CD000014.pub4.