Aniket D. Kulkarni, M.B., B.S., M.P.H., Denise J.
Jamieson, M.D., M.P.H., Howard W. Jones, Jr., M.D., Dmitry M. Kissin,
M.D., M.P.H., Maria F. Gallo, Ph.D., Maurizio Macaluso, M.D., Dr.P.H.,
and Eli Y. Adashi, M.D.
N Engl J Med 2013; 369:2218-2225
Background
The
advent of fertility treatments has led to an increase in the rate of
multiple births in the United States. However, the trends in and
magnitude of the contribution of fertility treatments to the increase
are uncertain.
Methods
We
derived the rates of multiple births after natural conception from data
on distributions of all births from 1962 through 1966 (before fertility
treatments were available). Publicly available data on births from 1971
through 2011 were used to determine national multiple birth rates, and
data on in vitro fertilization (IVF) from 1997 through 2011 were used to
estimate the annual proportion of multiple births that were
attributable to IVF and to non-IVF fertility treatments, after
adjustment for maternal age. Trends in multiple births were examined
starting from 1998, the year when clinical practice guidelines for IVF
were developed with an aim toward reducing the incidence of multiple
births.
Results
We
estimated that by 2011, a total of 36% of twin births and 77% of
triplet and higher-order births resulted from conception assisted by
fertility treatments. The observed incidence of twin births increased by
a factor of 1.9 from 1971 to 2009. The incidence of triplet and
higher-order births increased by a factor of 6.7 from 1971 to 1998 and
decreased by 29% from 1998 to 2011. This decrease coincided with a 70%
reduction in the transfer of three or more embryos during IVF
(P<0 .001="" 33="" a="" and="" attributable="" births="" decrease="" higher-order="" in="" ivf="" of="" p="" proportion="" the="" to="" triplet="">
Conclusions
Over
the past four decades, the increased use of fertility treatments in the
United States has been associated with a substantial rise in the rate
of multiple births. The rate of triplet and higher-order births has
declined over the past decade in the context of a reduction in the
transfer of three or more embryos during IVF. (Funded by the Centers for
Disease Control and Prevention.)
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