Internal electronic monitoring is the most accurate system for considering FHR and uterine contractions. A pressure sensing catheter is passed through the vagina, next to the fetus, into the uterine hole after the surfaces have ruptured and the cervix has distended to at least three cm.
The end of the catheter extending from the vagina is attached to a pressure recorder. As each contraction puts stress on the uterine contents, the pressure exerted on the catheter is recorded. When uterine contractions are monitored by internal pressure gauge, the frequency, duration, baseline strength, and top strengthof contractions can all be evaluated by the dimensions of the top of the contraction the tracing. Similarly crucial to guage is the return of the uterine tone to baseline strength between contractions. This guarantees placental filling between contractions. With contractions in the latest phase, the baseline level is less than five mm Hg ; with active contractions, it is roughly twelve mm Hg.
In the 2nd stage of work, the baseline might be as high as 20 mm Hg or below indicate uterine hypertonia and possible compromise of fetal contentment. The FHR recording is acquired from fetal scalp electrodes. When the fetal head is engaged, the electrode is inserted vaginally and attached to the fetal scalp.
A fetal electrocardiograph signal is got, intensified, and then fed into a cardiotachometer.
The output from the cardiotachometer is recorded on permanent graph paper. This level of info can’t be matched by external monitoring, which records only the frequency and period of contractions. The detail on fetal heartbeats is also more clear with internal monitoring. From the other viewpoint, internal monitoring is intrusive, carries the chance of uterine infection, and restricts the woman’s movement. Thus, it’s not used as customarily as external monitoring but is held back for girls that are specified as risky during work.