Placenta Accreta Interpregnancy Interval

Hi Henci,   I was wondering if you have seen this study and if you could explain it to me a little more.  I am sort of at a loss as to what all the numbers mean and what the difference is between delivery to conception and cesarean to conception. Mainly i am trying to figure out what they are saying the optimal time is between pregnancies/surgeries  Thanks!

http://www.ncbi.nlm.nih.gov/pubmed/11125633

Conn Med. 2000 Nov;64(11):659-61.

Interpregnancy interval as a risk factor for placenta accreta. 

Wax JR, Seiler A, Horowitz S, Ingardia CJ.

Source

University of Connecticut School of Medicine, USA.

Abstract

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 implanted placentas.

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 neonatal morbidity.

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. 

~ Henci