Conn Med. 2000 Nov;64(11):659-61.
Interpregnancy interval as a risk factor for placenta
Wax JR, Seiler A, Horowitz S, Ingardia CJ.
University of Connecticut School of Medicine, USA.
OBJECTIVE: To determine if the interval from a previous delivery
or cesarean to the next conception differs between patients with
abnormally adherent placentas as compared to those with normally
METHODS: We identified all histologically confirmed
placentas--accreta, increta, and percreta--at our hospital from
1992-1999. Subjects were excluded for primigravidity in the
affected pregnancy or inability to identify matched controls. Cases
were matched to the next three consecutive women delivering for
maternal age (> or = 35 years or < 35 years), placenta previa
(yes or no), prior cesarean (yes or no), prior uterine curettage
(yes or no), and prior vaginal delivery (yes or no). The primary
outcomes were delivery-to-conception and cesarean-to-conception
intervals. Secondary outcomes included measures of maternal and
RESULTS: Delivery-to-conception intervals for cases and controls
were 37.1 +/- 18.7 months and 37.9 +/- 22.7 months, respectively (P
= .91). Cesarean-to-conception intervals for cases and controls
were 35.2 +/- 18.2 and 48.1 +/- 31.0 months, respectively (P =
.35). Cases were more likely to require uterine curettage (54.5 vs
0%), hysterectomy (81.8 vs 0%), and transfusion (72.7 vs 0%), all P
< .001. Subjects with accreta delivered earlier (31.7 +/- 9.4 vs
38.1 +/- 2.6 weeks, P = .054) and smaller infants (2,158 +/- 1,180
g vs 3,159 +/- 781 g, P = .006) who were more likely to have
five-minute Apgar scores < 7 (18.2% vs 0%, P = .038).
CONCLUSIONS: Cesarean-to-conception intervals but not
delivery-to-conception intervals are shorter in patients with
abnormally adherent placentas. Placenta accreta is associated with
significant maternal and perinatal morbidity.
I've pasted in the abstract of the study for convenience.
Unfortunately, I can't get a copy of the actual journal article as
it's not in a major journal. As far as I can make out from the
abstract alone, the authors conclude that women with
placenta accreta (cases) had shorter intervals from when they
had the cesarean to conception of the next pregnancy than women who
had cesareans but didn't develop placenta accreta (controls). This
was not true for women who had accreta and had (presumably
vaginal) delivery in the prior pregnancy (cases) versus women with
vaginal delivery who didn't have accreta (controls). Except that
the p value, the probability that the difference wasn't due to
chance, was 0.35, much higher than 0.05, the usual threshold
for determining statistical significance. The usual threshold means
that there is a 5 in 100, or 1 in 20, probability that the
difference is due to chance. Without the study itself,
I can't tell more about why they came to this conclusion when
the p value didn't justify it. The rest of the outcomes
reported in the abstract were what you would expect, that is, women
with placenta accreta are at very high risk for severe
complications compared with women who don't have accreta.