Cervical Length and Thickness of Placental Edge Predict Bleeding

This study shows that the length of your cervix and the thickness of your placental edge can be indictors for your risk of bleeding. It looks like 22 of the 54 previa cases actually bled, so still less than 50%.

Does cervical length and the lower placental edge thickness measurement correlates with clinical outcome in cases of complete placenta previa?

Authors :Zaitoun MM; El Behery MM; Abd El Hameed AA; Soliman BS

Author Address:Zagazig University, Zagazig, Egypt.Source:Archives Of Gynecology And Obstetrics [Arch Gynecol Obstet] 2011 Oct; Vol. 284 (4), pp. 867-73.

Objectives: To evaluate the effectiveness of cervical length and the lower placental edge thickness measurement in predicting the risk of antepartum hemorrhage (APH) and emergency preterm cesarean delivery in women with complete placenta previa.
Methods: Fifty-four cases with confirmed diagnosis of complete placenta previa in third-trimester were subjected to transvaginal sonographic measurement of cervical length and lower placental edge thickness and correlated this to clinical outcome with regards to gestational age at delivery, ante partum hemorrhage, emergency cesarean section before 36 weeks due to massive hemorrhage and neonatal birth weight.
Results: Antepartum bleeding and emergency cesarean section rate before 36 weeks due to massivebleeding were significantly higher in cases with thick lower placental edge or central placenta than cases with thin lower placental edge [16 cases (53.3%) vs. 5 cases (20.8%)] for the former and [14 cases (46.6%) vs. 4 cases (16.6%) for the later]. Antepartum bleeding was observed in 18 cases (51.4%) when cervical length measurements ≤30 mm of whom 16 cases (88.9%) had showed severe attack necessitated emergency cesarean delivery before 36 weeks versus 4 cases (21.1%) with cervical length ≥30 mm. By combining cervical length with lower placental edge thickness measurement sensitivity, specificity, positive predictive value (PPV) negative predictive value (NPV) and accuracy increased to 83.3, 78.4, 53.4, 79.8 and 89.7%, respectively for the prediction of antepartum bleeding and emergency cesarean section <36 weeks using receiver-operating characteristics curve with area under the curve 0.882.
Conclusion: Short cervical length at cut-off value ≤30 mm and increased lower placental edge thickness measurements may predict with high accuracy the risk of APH and emergency preterm cesarean delivery in patients with complete placenta previa.


Read This First

First: I AM NOT AN EXPERT. I am just a woman who was diagnosed with previa. I obsessively researched the condition on peer reviewed journal articles and decided to share what I found. I don’t understand all of what is written in every abstract.

Second: MY SOURCES ARE EXPERTS. Everything published on this site comes from peer reviewed academic journal articles. What I often include in the post is the ‘abstract’ of a study, which is a brief overview of the study, the results, and the conclusions.


This site is just to post information I found and is not likely to be updated. If you want to read lots of stories about women’s experiences with placenta previa, you should visit:

Placenta Previa Stories by Alissa

Direct link: http://www.placentapreviastories.blogspot.com/

How Likely Are You To Bleed?

In this study, 56% of women bled. That seems to be pretty consistent with what I see in other studies.

Can ultrasonography of the placenta previa predict antenatal bleeding?

Authors:Hasegawa J; Higashi M; Takahashi S; Mimura T; Nakamura M; Matsuoka R; Ichizuka K; Sekizawa A; Okai T

Author Address: Department of Obstetrics and Gynecology, Showa University School of Medicine, Tokyo, Japan.Source:Journal Of Clinical Ultrasound: JCU [J Clin Ultrasound] 2011 Oct; Vol. 39 (8), pp. 458-62. Date of Electronic Publication: 2011 Jun 10.

Purpose: To evaluate the abnormal sonographic (US) findings in patient with placenta previa and bleeding.
Methods: A total of 182 cases of singleton pregnancies with placenta previa were reviewed. The US findings including the type of placenta previa, placental location, presence of placenta lacunae, lack of clear zone, sinus venosus at the margin of the placenta, velamentous cord insertion, sponge-like echo in the cervix and cervical length were evaluated in relation to episodes of bleeding that required in-patient treatment during pregnancy and/or emergency cesarean section.
Results: Episodes of antenatal bleeding occurred in 102/182 (56%) patients with placenta previa. An emergency cesarean section was performed in 66 (64.7%) of these 102 patients. In the 80 patients without episodes of antenatal bleeding, an emergency cesarean section was performed in only 1 (1.3%). Detection of US findings just prior to cesarean section was not associated with the need for emergency cesarean section due to uncontrollable bleeding from the placenta previa. Frequencies of each US finding at 20 weeks of gestation were not different between the patients who underwent emergency cesarean sections and the others. Frequency of marginal sinus was slightly higher in cases with bleeding episode (16% versus 0%, p < 0.05), but the other US findings were not associated with the occurrence of bleedingepisodes during pregnancy.
Conclusions: No US finding could predict bleeding episodes and the eventual need for an emergency cesarean section. The obstetrician should be aware that sudden bleeding during pregnancy may occur in patients with placenta previa, even in the absence of any other US findings.

Another study showing shorter cervix means more risk for bleeding

Correlation between the cervical length and the amount of bleeding during cesarean section in placenta previa.

Authors:Mimura T; Hasegawa J; Nakamura M; Matsuoka R; Ichizuka K; Sekizawa A; Okai T

Author Address:Department of Obstetrics and Gynecology, Showa University School of Medicine, Tokyo, Japan.t365kayo@e-ml.netSource:The Journal Of Obstetrics And Gynaecology Research [J Obstet Gynaecol Res] 2011 Jul; Vol. 37 (7), pp.830-5.


Aim: To investigate the association between the amount of bleeding during a cesarean section and the effacement of the uterine cervix in patients with placenta previa.
Methods: This study reviewed 115 singleton pregnancies with placenta previa. In cases of placentaprevia, the thickness of the uterine muscle and cervical length were retrospectively measured and compared with the amount of bleeding during the cesarean section.
Results: No correlation was found between the amount of bleeding during the cesarean operation and the thickness of the uterine isthmus. There was a significantly negative correlation between the amount ofbleeding and cervical length (r = -0.344, P < 0.001). The threshold cervical length associated with massive bleeding (>2500 mL) was 25 mm, based on an ROC curve. The relative risk for massive bleedingin cases with a short cervical length (<25 mm) was 7.2 (95% CI, 2.3-22.3) in comparison to cases with a long cervical length.
Conclusions: This study demonstrated that a short cervical length in cases with placenta previa was associated with massive bleeding during the operation. Short cervical length seems to be one of the warning signs for massive bleeding during the operation for placenta previa.
(© 2011 The Authors. Journal of Obstetrics and Gynaecology Research © 2011 Japan Society of Obstetrics and Gynecology.)

What Is Helpful To Know About Your Previa

If you are trying to understand your risks for certain things, knowing the answers to some of these questions will help you figure it out. (Some you will know, some you may need to get from your OB.)

  • How many weeks were you at your most recent ultrasound?
  • What type of previa do you have? (low-lying, marginal/partial, or complete?)
  • Is your previa anterior (on the front of your uterus), posterior (at the back), or central (centered on the cervix)?
  • How far away from or over the os is your previa? (The os is the opening to your cervix; this measurement is usually in centimeters or millimeters.)
  • How long is your cervix?
  • Have you had a previous c-section? How many?

Anterior Previa Moves Faster than Posterior Previa

If your previa is anterior, it is on the front part of your uterus. If you previa is posterior, it is on the back part of your uterus. Ask your OB if your previa is anterior or posterior. Anterior previas move more quickly (averaging 2.6 mm per week) than posterior previas (averaging 1.6 mm per week).

Difference in migration of placenta according to the location and type of placenta previa.

Cho JY, Lee YH, Moon MH, Lee JH.


Department of Radiology and Institute of Radiation Medicine, Seoul National University College of Medicine, 28, Yeongeon-dong, Jongno-gu, Seoul 110-744, Korea.



To correlate the incidence and rate of placental migration with the mode of delivery, pregnancy outcome, and maternal complication according to the location (anterior versus posterior) and type of placenta previa (PP).


We prospectively evaluated the placentas of 98 pregnant women with PP or low-lying placenta (LLP) at the prenatal sonographic examination performed between 20 and 27 gestational weeks. We divided the pregnant women into groups according to type and location of PP. Follow-up sonographic examination was performed between 32 and 37 weeks. We compared incidence of migration to the normal position and calculated the migration rate as the migrated distance divided by the weeks of interval between 2 sonographic examinations. We compared the incidences of cesarean section, fetal outcome, and maternal complications during the pregnancy.


The incidence of migration in the group of anterior placentas was significantly higher than that in the group of posterior placentas. The mean migration rate in the anterior group was 2.6 mm/week, whereas that in the posterior group was 1.6 mm/week. The migration rate of incomplete PP was significantly higher than that of LLP. Incidence of cesarean section for nonmigrated PP was significantly higher in the posterior group. The incidences of premature delivery and vaginal spotting were also significantly higher in the posterior group.


Anterior PP and LLP may migrate more often and faster than posterior PP

Placental Symmetry and Persistent Placenta Previa

This study indicates that placentas that are centered over the cervix in the second trimester are most likely to persist. Also worth noting, only 22 of the 43 women whose previa persisted actually bled. (Just less than half.)

It says ‘most likely’, but I still don’t understand exactly HOW MANY of the original group with centered previas persisted. (What does sensitivity of 49% mean?)

Second trimester sonographically diagnosed placenta previa: prediction of persistent previa at birth.

Zelop CC, Bromley B, Frigoletto FD Jr, Benacerraf BR.


Department of Obstetrics and Gynecology, Brigham & Women’s Hospital, Harvard Medical School, Boston, MA.



We sought to determine the natural history of second trimester sonographically diagnosed placenta previa, and to ascertain whether the position of the placenta with respect to the cervical os at second trimester sonography can accurately predict persistence of the placenta previaat term.


The study population included all women consecutively diagnosed by ultrasound with placenta previa between 14 and 20 weeks’ gestation. Medical records of the patients requiring cesarean section were reviewed to determine the presence of placenta previa. We reviewed the second trimester sonogram of patients who underwent abdominal delivery for placental and nonplacental indications to determine whether the central (symmetrical) versus the partial (asymmetrial) position of the placenta with respect to the internal os predicted the presence of placenta previa at delivery.


A total of 925 second trimester- patients were sonographically identified as having placenta previa. Two hundred and sixty seven patients underwent cesarean delivery, 43 of which had placenta previa (43/925 or 4.6%). Twenty-two of the 43 were asymptomatic without antepartum bleeding. Analysis of the second trimester position of the placenta revealed that symmetry of the placenta with respect to the internal os at second trimester scan had a sensitivity of 49% for prediction of placenta previa at birth.


The degree of placental symmetry with respect to the internal os during the second trimester successfully predicted the previas most likely to persist at delivery with a sensitivity of 49% (95% CI 34-64) and specificity of 93%.

Association of maternal serum alpha-fetoprotein with persistent placenta previa.

I don’t know what this is, but it makes me wonder if there is a blood test that could indicate the likelihood of a previa persisting.


Koster EL, Dashe JS, McIntire DD, Ramus RM.


Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center at Dallas, TX 75390-9032, USA.



To evaluate the relationship between maternal serum alpha-fetoprotein (MSAFP) and the risk of persistent placenta previa.


We conducted a retrospective cohort study of singleton pregnancies with sonographic evidence of placenta previa at 15-20 weeks’ gestation, between October 1991 and August 2000. Only pregnancies with MSAFP determination at 15-20 weeks’ gestation and non-anomalous live-born infants > or =24 weeks’ gestation were included. Pregnancies in which Cesarean delivery was performed for placenta previa were considered persistent; this was the primary outcome.


Of 275 women with previa at 15-20 weeks’ gestation, 33 (12%) had previa at delivery. Trend analysis revealed a greater likelihood ofpersistent previa with increasing MSAFP values (p=0.01). Mid-trimester MSAFP <1 multiple of the median (MoM) was associated with a decreased incidence of persistence of 4%, significantly less than the risk at > or =1 MoM (16%; p=0.01).


There is an association between increasing MSAFP values and greater likelihood of persistent placenta previa. An MSAFP value <1 MoM is associated with a reduction in the risk of persistence of previa to delivery.



[PubMed – indexed for MEDLINE]