Placenta Previa in the Second Trimester: Sonographic and Clinical Factors Associated with Its Resolution

ABSTRACT

We identify characteristics that predict resolution of placenta previa and develop a clinical model for likelihood of resolution. We conducted a retrospective study of 366 singleton pregnancies complicated by placenta previa diagnosed with resolution of the previa as the primary outcome. Regression analyses were performed to determine variables associated with resolution and optimal timing for repeat sonographic evaluation. A likelihood of resolution model was created using a parametric survival model with Weibull hazard function. Of the 366 cases, 84% of complete placentae previae and 98% of marginal placentae previae resolved at a mean gestational age of 28.6 ± 5.3 weeks. Only gestational age and distance from the internal cervical os at the time of diagnosis were significantly associated with resolution (p < 0.01). Likelihood of resolution was not significantly associated with any other variables. Marginal previae diagnosed in the second trimester do not appear to warrant repeat ultrasound evaluation for resolution.

KEYWORDS

Placenta previa - marginal previa - bleeding - pregnancy - resolution

REFERENCES

• 1 Rosati P, Guariglia L. Clinical significance of placenta previa detected at early routine transvaginal scan.  J Ultrasound Med. 2000;  19 581-585
• 2 Zelop C C, Bromley B, Frigoletto Jr F D, Benacerraf B R. Second trimester sonographically diagnosed placenta previa: prediction of persistent previa at birth.  Int J Gynaecol Obstet. 1994;  44 207-210
• 3 Rizos N, Doran T A, Miskin M, Benzie R J, Ford J A. Natural history of placenta previa ascertained by diagnostic ultrasound.  Am J Obstet Gynecol. 1979;  133 287-291
• 4 Lauria M R, Smith R S, Treadwell M C et al.. The use of second-trimester transvaginal sonography to predict placenta previa.  Ultrasound Obstet Gynecol. 1996;  8 337-340
• 5 Miller D A, Chollet J A, Goodwin T M. Clinical risk factors for placenta previa-placenta accreta.  Am J Obstet Gynecol. 1997;  177 210-214
• 6 Zhang J, Savitz D A. Maternal age and placenta previa: a population-based, case-control study.  Am J Obstet Gynecol. 1993;  168 641-645
• 7 Ghourab S, Al-Jabari A. Placental migration and mode of delivery in placenta previa: transvaginal sonographic assessment during the third trimester.  Ann Saudi Med. 2000;  20 382-385
• 8 Dashe J S, McIntire D D, Ramus R M, Santos-Ramos R, Twickler D M. Persistence of placenta previa according to gestational age at ultrasound detection.  Obstet Gynecol. 2002;  99 (5 Pt 1) 692-697
• 9 Laughon S K, Wolfe H M, Visco A G. Prior cesarean and the risk for placenta previa on second-trimester ultrasonography.  Obstet Gynecol. 2005;  105 (5 Pt 1) 962-965
• 10 Cho J Y, Lee Y H, Moon M H, Lee J H. Difference in migration of placenta according to the location and type of placenta previa.  J Clin Ultrasound. 2008;  36 79-84
• 11 Ananth C V, Demissie K, Smulian J C, Vintzileos A M. Placenta previa in singleton and twin births in the United States, 1989 through 1998: a comparison of risk factor profiles and associated conditions.  Am J Obstet Gynecol. 2003;  188 275-281
• 12 Cox C, Chu H, Schneider M F, Muñoz A. Parametric survival analysis and taxonomy of hazard functions for the generalized gamma distribution.  Stat Med. 2007;  26 4352-4374