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 is vertical.
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 (Obstet.
"We may need a whole new
labor curve for these women," Dr.
