Reduced fetal movements can represent fetal distress, as a method of fetal compensation to reduce oxygen consumption as a response to chronic hypoxia in utero

Normal physiology

• Fetal movements should be established by 24 weeks gestation
• The first onset of recognised fetal movements is known as quickening
  • This usually occurs between 18-20 weeks gestation, and increase until 32 weeks gestation at which point the frequency of movement tends to plateau
  • Multiparous women will usually experience fetal movements sooner, from 16-18 weeks gestation
• Towards the end of pregnancy, fetal movements should not reduce
• Expectant mothers will usually quickly recognise a pattern to these movements
  • The nature of the movements themselves can be very variable
  • There is no established definition for what constitutes reduced fetal movements (RFM), but the RCOG considers less than 10 movements within 2 hours (in pregnancies past 28 weeks gestation) an indication for further assessment

Aetiology

Risk factors

• Posture: there can be positional changes in fetal movement awareness, generally being more prominent during lying down and less when sitting and standing
• Distraction: awareness of fetal movements can be distractable, and if a woman is busy or concentrating on something else, these can be less prominent
• Placental position: patient with anterior placentas prior to 28 weeks gestation may have lesser awareness of fetal movements
• Medication: both alcohol and sedative medications like opiates or benzodiazepines can temporarily cause reduced fetal movements
• Fetal position: anterior fetal position means movements are less noticeable
• Body habitus: obese patients are less likely to feel prominent fetal movements
• Amniotic fluid volume: both oligohydramnios and polyhydramnios can cause reduction in fetal movements
• Fetal size: up to 29% of women presenting with RFM have a SGA fetus

Investigations

• Fetal movements are usually based solely on maternal perception, though it can also be objectively assessed using handheld Doppler or ultrasonography
• As per RCOG Green-top guidelines, investigations are dependent of gestation at onset of RFM
• If past 28 weeks gestation:
  • Initially, handheld Doppler should be used to confirm fetal heartbeat
  • If no fetal heartbeat detectable, immediate ultrasound should be offered
  • If fetal heartbeat present, CTG should be used for at least 20 minutes to monitor fetal heart rate which can assist in excluding fetal compromise
  • If concern remains, despite normal CTG, urgent (within 24 hours) ultrasound can be used - should include abdominal circumference or estimated fetal weight (to exclude SGA), and amniotic fluid volume measurement