Reduced fetal movements
Introduction
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. This is concerning, as it reflects risk of stillbirth and fetal growth restriction. It is believed that there may also be a link between reduced fetal movements and placental insufficiency.
Physiology
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.
Epidemiology
Fetal movements should be established by 24 weeks gestation.
Reduced fetal movements is a fairly common presentation, affecting up to 15% of pregnancies. 3-5% of pregnant women will have recurrent presentations with RFM.
Risk factors for reduced fetal movements
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. Ultrasound assessment should include abdominal circumference or estimated fetal weight (to exclude SGA), and amniotic fluid volume measurement
If between 24 and 28 weeks gestation, a handheld Doppler should be used to confirm presence of fetal heartbeat.
If below 24 weeks gestation, and fetal movements have previously been felt, a handheld Doppler should be used.
If fetal movements have not yet been felt by 24 weeks, onward referral should be made to a maternal fetal medicine unit.
If RFM are recurrent, further investigations are also required to consider structural or genetic fetal abnormalities.
Prognosis
Concern regarding absent or reduced fetal movements stems for the potential for this presentation to represent fetal distress or impending demise. Between 40-55% of women who suffer from stillbirth experience reduced fetal movements prior to diagnosis.
However, in 70% of pregnancies with a single episode of reduced fetal movement, there is no onward complication.
