Handbook CTG. Glossary

 Glossary

Augmentation of labour:

The process of artificially stimulating the uterus to increase the frequency, duration and

int

ensity of uterine contractions after the onset of spontaneous labour. It is indicated when

lab

our is progressing slowly or not progressing at all so as to avoid the complications

secondary to prolonged labour.

Bradycardia:

A baseline fetal heart rate <110 bpm for at least 10 minutes.

Cardiotocography – CTG:

A graphic record of the fetal heart rate and uterine contractions through an ultrasound

device placed on the maternal abdomen or through a fetal scalp electrode. The ‘toco’,

registers the uterine contractions through a second transducer placed on the uterine fundus.

Induction of labour – IOL:

The process of artificially initiating the onset of labour so as to optimize maternal and/or

fetal outcome by avoiding continuation of pregnancy.

Intermittent auscultation:

A method of intrapartum surveillance where the fetal heart rate is heard for short periods of

time at prespecified intervals.

Intrapartum bleeding:

Any bleeding from the genital tract that is heavier than the usually expected blood-stained

mucus discharge during labour.

Intrapartum reoxygenation ratio – IRR:

The ratio between cumulative uterine relaxation and uterine contraction times over 30

minutes indicates the total duration of time available for reoxygenation of placental venoussinuses, immediately after a uterine contraction during a 30-minute period. IRR >1 (i.e.

relaxation time is more than the time spent during a contraction) is unlikely to lead to fetal

hypoxia and acidosis.

Intrauterine resuscitation:

Any intervention undertaken during labour with the aim/intention to improve oxygen

delivery to the fetus by improving the intrauterine environment.

Meconium:

Fetal bowel content that is passed into the amniotic fluid in about 10 percent of term

lab

ours. The term meconium-stained amniotic fluid is used to describe this situation. The

terms “light” meconium staining and “heavy” meconium staining are recommended with the

former representing a situation that is most likely physiological with a large volume of

amniotic fluid indicating a lower risk of placental insufficiency or prolonged ruptured

membranes, and the latter indicating a situation in which the fetus may have

oligohydramnios due to placental insufficiency, prolonged prelabour rupture of membranes

or a long labour and is thus more likely to be associated with hypoxia or infection.

MHR:

Maternal heart rate. Erroneous recording of MHR on cardiotocography may be

misinterpreted as the fetal heart rate (FHR)

Operative vaginal delivery (with vacuum or forceps)/cesarean delivery:

These are options for management of “pathological” (or a ‘category 3’) cardiotocography

observed during second stage of labour.

Peripheral tests of fetal well-being:

These are aimed at testing a sample of blood taken from fetal scalp to determine fetal

acidosis (fetal scalp pH or scalp lactate) or to assess oxygenation saturation from fetal skin

(fetal pulse oximetry).

Preterm:

All fetuses between 24 weeks (considered as the limit of viability) and 37 completed weeks

(the 259th day).

Prolonged deceleration:Fall from baseline fetal heart rate of >15 beats per minute lasting longer than 3 minutes.

Sinusoidal pattern:

A regular oscillation of baseline variability in a smooth undulating pattern lasting at least 10

minutes with a frequency of 3–5 cycles per minute and an amplitude of 5 to 15 bpm above

and below the baseline.

STAN:

A system of intrapartum monitoring that records changes in fetal ECG during labour. It

analyses the ‘ST segment’ and the ‘T-wave’ of the fetal ECG complex.

Uterine scar:

Any interruption in the integrity of the myometrium and its subsequent replacement by scar

tissue before pregnancy. Although a previous caesarean section is the most common cause

of uterine scarring, a previous myomectomy, uterine perforation/rupture, resection of

cornual ectopic pregnancy and any other procedure that involves an interruption of the

myometrium with subsequent replacement by scar tissue may weaken the uterine wall,

predisposing to uterine scar dehiscence or rupture.

Zig-zag (saltatory) autonomic instability pattern:

Fetal heart amplitude changes of >25 bpm with an oscillatory frequency of >6 per minute

for a minimum duration of 1 minute.