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.