This month's Master Class highlights a critical area of obstetrics where the convergence of technology, clinical observation, and research stimulated a change in practice guidelines: the use of the labor curve
to monitor normal versus abnormal labor.
Over the past year, much attention has been devoted to labor curves
. Is the original Friedman labor curve
, which dates to the 1950s, still applicable today?
The labor curve
of the grand mulipara: Does progress of labor continue to improve with additional childbearing?
The parameter -b is the slope of the macroeconomic supply of labor curve
in (w - p, u) space, and is the slope of the labor demand curve in that space.
It is the combination of this wage setting (which is in the self-interest of the owners of the firms as distinct from that of its employees) with an upward-sloped labor curve
that produces these results.
Therefore, the marginal product curve in Figure 1 has been shifted down by a factor of (1 - 1/6) = 5/6 to obtain the dashed-line demand for labor curve
for a firm.(6) As noted above, the downward adjustment of the marginal product curve can be skipped in an introductory course.
So, for w [less than or equal to] [w.sup.*], the demand for labor curve
The slope of the labor curve
, however, is not important for the principles of the subsequent analysis.
We have a new labor curve
to guide us--one that shows us, for example, that active labor occurs most commonly after 6 cm dilation rather than 4 cm as we'd previously thought.
When contemporary data from the Consortium on Safe Labor were applied to the original Friedman labor curve
, investigators found that the active phase of labor may be slower than previously thought.
These findings of an overall longer duration and slower progression of the early part of the first stage of labor have led to a proposal for adoption of a separate obese labor curve
"We may need a whole new labor curve
for these women," Dr.