Interpretation
Most of the women were in the age group between 22 to 26 years. The mean
age of our study was 24.84±3.49 years in group A and 24.62± 3.70 in
group B. Our mean age is comparable to the recent
studies7-9, which is different from other labor
studies which were done century past by Friedman et
al1-3. It may be explained as a result of increase in
age of marriages and delayed child birth.
The median duration of active phase of labor from 4 cm was 5hours in
group A and 5.21 hours in group B. Observation of different studies like
Zhang et al, also shows similar median active phase
duration6-9. Friedman reported mean duration of 4.4
hours for the active labor duration among nulliparous females. This mean
duration was similar to the observation of others in
1960s13.
The upper limit of normal, i.e. mean+2SD is 9 hours and 6 hours
respectively in progression from 4cm and 6cm to full dilatation. Similar
to us, other recent studies are also reporting that low-risk nulliparous
women who are delivering vaginally and undergoing spontaneous delivery
without oxytocin, epidurals, and operative deliveries have duration
between 6.2-7.7 hours at the mean and up to 13.4-19.4 hours at the mean
+ 2SD14. Friedman’s upper limit of normal (mean+2SD)
was 11.7 hours and his active phase began from 2.5cm cervical dilatation
and his 45-53% of active phase duration was passed in the acceleration
phase when only dilatation changes from 2.5cm to 4
cm1-3. The mean duration in progressing from 6cm to 10
cm cervical dilatation (i.e. almost similar to phase of maximum slope
according to Friedman) in our study was 2.57±1.31 hours in Group A and
2.79 ±1. 72 hours in group B. The mean duration of phase of maximum
slope, i.e. from 4cm to 9 cm, of Friedman study was found to be
1.67±1.25 hours1-3.
Coming to the labor pattern curve, our curve has only acceleration phase
and phase of maximum slope. The original Friedman’s curve also had
latent phase and deceleration phase. We did not plot latent phase. On
comparing with Friedman curve, our curve was flatter than him and there
is no rapid uprise at 4-5 cm. Our mean slope was 1.1 cm/hour and
Friedman’s mean slope was 1.6cm/hour. The mean rate of dilatation in the
phase of maximum slope in Friedman’s curve was twice as high i.e. 3
cm/hour. At mean- 2SD, minimum active phase dilatation rate in both
groups was 0.6cm/hour, which represents slowest yet normal labor in our
study. Since Friedman didn’t calculated minimum slope, if his curve was
extrapolated it was 1.2 cm /hour15. This was twice as
reported by our study observations and other recent studies. We have
also observed that even if labor progresses at <1cm/hour,
vaginal delivery can still be achieved. We have also found that slope of
labor curve changes after 6cm in both groups which was observed on
Friedman’s curve at 4 cm, so we can consider it as the onset of active
phase. Our findings provide new data from the perspective of South Asian
population. The observations reported in similar studies by
Zhang6-8 in the US, Suzuki in
Japan16, Shi in china9, and their
colleagues, which suggest that labour progresses more slowly than
previously thought. In a recent study by Oladapo et al, any
interventions done to expedite labor, especially before 5 cm to conform
a cervical dilatation threshold of 1 cm/hour, is inappropriate, in both
nulliparous and multiparous women. Their 95thpercentile values from one
level of dilatation to the next during the traditional active phase
yielded median rates between 0.1 and 0.5 cm/hour between 4 and 10
cm17.We did not plot deceleration phase in majority of
curves, but often in women with protraction and arrest disorder. It
suggests that deceleration phase is an indicator for dystocia. Without
the “deceleration phase,” the slope of the active phase in our curve
is less steep than the Friedman curve. This will have a significant
impact on the definitions of active phase protraction and arrest
disorder.
Recently in 2018, WHO also supported by observing new evidences. Now 5
cm is cut off for both nulliparous and multiparous for commencement of
active phase18. National Institute for Health and Care
Excellence guidelines for intrapartum care, have also been modified to
state a minimum acceptable rate of progress in active first stage is
0.5cm per hour19.