Diagnosis of low-lying placenta: can migration in the third trimester predict outcome?

Iron deficiency anaemia associated with increased placenta praevia and placental abruption: a retrospective case-control study

BACKGROUND/OBJECTIVES

A few studies reported association between placenta praevia (PP) and placental abruption (PA) with maternal iron deficiency anaemia (IDA), which is not an established risk factor for these conditions. This retrospective case-control study was performed to determine the relationship between IDA with PP and PA.

METHODS

Maternal characteristics, risk factors for and incidence of antepartum haemorrhage overall, and PP and PA, were compared between women with IDA only and controls without IDA or haemoglobinopathies matched for exact age and parity (four controls to each index case), who carried singleton pregnancy to ≥22 weeks and managed under our care from 1997 to 2019.

RESULTS

There were 1,176 women (0.8% of eligible women in the database) with IDA only, who exhibited slightly but significantly different maternal characteristics, and increased antepartum haemorrhage overall (3.4% versus 2.2%, p = 0.031, OR 1.522, 95% CI 1.037-2.234) and PP (1.8% versus 0.9%, p = 0.010, OR 1.953, 95% CI 1.164-3.279), but not PA (1.2% versus 1.1%, p = 0.804, OR 1.077, 95% CI 0.599-1.936). When stratified by parity status, increased PP was found in nulliparous women only. On multivariate analysis adjusting for parity, previous abortion history, overweight and obesity, short stature, other antenatal complications as a composite factor, preterm (<37) delivery, previous caesarean delivery, and infant gender, IDA was associated with PP (aOR 3.485, 95% CI 1.959-6.200) and PA (aOR 2.181, 95% CI 1.145-4.155).

CONCLUSIONS

Both PP and PA are increased in women with IDA, the prevention of which could be a means to reduce the occurrence of both PP and PA.

Patients with resolution of low-lying placenta and placenta previa remain at increased risk of postpartum hemorrhage

OBJECTIVE

To determine whether women who experience resolution of low placentation (low-lying placenta or placenta previa) are at increased risk of postpartum hemorrhage compared to those with normal placentation throughout pregnancy.

METHODS

This was a retrospective cohort study of women who delivered at Mount Sinai Hospital between 2015 and 2019, and who were diagnosed with low-lying placenta or placenta previa on transvaginal ultrasound at the time of the second-trimester anatomical survey, with resolution of low placentation on subsequent ultrasound examination. Women undergoing second-trimester anatomical survey who had normal placentation on transvaginal ultrasound 3 days before or after the cases were randomly identified for comparison. The primary outcome was the rate of postpartum hemorrhage. Secondary outcomes included the need for a blood transfusion, use of additional uterotonic medication, the need for additional procedures to control bleeding, and maternal admission to the intensive care unit. Outcomes were assessed using a multivariable logistic regression model.

RESULTS

A total of 1256 women were identified for analysis, of whom 628 had resolved low placentation and 628 had normal placentation. Women with resolved low placentation, compared to those with normal placentation throughout pregnancy, had significantly higher mean age (33.0 ± 5.4 years vs 31.9 ± 5.5 years; P < 0.01) and lower mean body mass index at delivery (27.9 ± 5.5 kg/m² vs 30.2 ± 5.7 kg/m² ; P < 0.01), and were more likely to have undergone in-vitro fertilization, be of non-Hispanic white race, have posterior placental location (all P < 0.01) and have private/commercial health insurance (P = 0.04). Patients with resolved low placentation vs normal placentation had greater odds of postpartum hemorrhage (adjusted odds ratio (aOR), 3.5 (95% CI, 2.0-6.0); P < 0.01), use of additional uterotonic medication (aOR, 2.2 (95% CI, 1.5-3.1); P < 0.01) and increased rates of additional procedures to control bleeding (aOR, 4.0 (95% CI, 1.3-11.9); P = 0.01).

CONCLUSION

Despite high rates of resolution of low-lying placenta and placenta previa by term, women with resolved low placentation remain at increased risk of postpartum hemorrhage compared to those with normal placentation throughout pregnancy. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Pregnancy and Delivery Outcomes in Women With Persistent Versus Resolved Low-Lying Placenta in the Late Third Trimester

OBJECTIVES

The safest mode of delivery in low-lying placenta is debatable. Little is known about outcomes in low-lying placenta resolved during the late third trimester. We compare outcomes of women with persistent versus resolved low-lying placenta.

METHODS

A retrospective analysis on a prospective cohort of women with low-lying placenta confirmed at 28-30 weeks sonography (01/2009 to 03/2018). Women were followed up serially every 2 to 3 weeks until delivery to assess the placental edge-to-internal os distance (IOD), and included if scan was performed within 28 days before delivery.

RESULTS

There were 86 women: in 21 the low-lying placenta resolved, whereas in 65 persisted (n = 15 IOD 1-10 mm, n = 50 IOD 11-20 mm). Antepartum bleeding associated with higher rates of urgent cesarean delivery in 1-10 mm (P = .041) but not in 11-20 mm (P = 1.000) and >20 mm (P = .333). Among women with IOD >10 mm allowed to labor, vaginal delivery occurred in 76.7% (11-20 mm) and 94.1% (>20 mm) (P = .155), with no difference according to parity (70% and 80% in multiparas, P = .696; 60% and 72.7% in nulliparas, P = .698). Severe PPH (P = .922) and hemoglobin drop (P = .109) were similar among groups. Women with IOD 11-20 mm and >20 mm and vaginal delivery bled less than women with similarly located placenta and cesarean delivery (P = .009 and P = .048).

CONCLUSIONS

Women with IOD >10 mm have high chances of deliver vaginally with no further increase of their hemorrhagic risk. Success of vaginal delivery is independent of parity and antepartum bleeding. Labor should be managed in an adequate hospital setting.

Ultrasound as a Sole Modality for Prenatal Diagnosis of Placenta Accreta Spectrum: Potentialities and Pitfalls

Background  Placenta accreta spectrum (PAS) is a significant cause of maternal and neonatal mortality and morbidity. Its prevalence has been rising considerably, primarily due to the increasing rate of primary and repeat cesarean sections. Accurate prenatal identification of PAS allows optimal management because the timing of delivery, availability of blood products, and recruitment of skilled anesthesia, and surgical team can be arranged in advance.

Aims and Objectives  This study aimed to (1) study the ultrasound and color Doppler features of PAS, (2) correlate imaging findings with clinical and per-operative/histopathological findings, and (3) evaluate the accuracy of ultrasound for the diagnosis of PAS in patients with previous cesarean section.

Materials and Methods  This prospective study was conducted in radiology department of a tertiary care hospital. After screening 1,200 pregnant patients, 50 patients of placenta previa with period of gestation ≥ 24 weeks and history of at least one prior cesarean section were included in the study. Following imaging features were evaluated: (1) gray scale covering intraplacental lacunae, disruption of uterovesical interface, myometrial thinning, loss of retroplacental clear space, and focal exophytic masses; and (2) color Doppler covering intraplacental lacunar flow, hypervascularity of uterine serosa–bladder wall interface, and perpendicular bridging vessels between placenta and myometrium.

Study Design  Present study is a prospective one in a tertiary care hospital.

Results  Of the 19 PAS cases, 18 were correctly diagnosed on ultrasonography (USG) and confirmed either by histopathological analysis of hysterectomy specimen or per-operatively due to difficulty in placental removal. PAS was correctly ruled out in 27 of 31 patients. The diagnostic accuracy of USG was 90%. The sensitivity, specificity, positive, and negative predictive values were 94.7, 87.1, 81.8, and 96.4%, respectively.

Conclusion  Ultrasound is indispensable for the evaluation of pregnant patients. It is an important tool for diagnosing PAS, thereby making the operating team more cautious and better equipped for difficult surgery and critical postoperative care. It can be relied upon as the sole modality to accurately rule out PAS in negative patients, thereby obviating unnecessary psychological stress among patients due to possible hysterectomy.

Guideline No. 402: Diagnosis and Management of Placenta Previa

OBJECTIVES

To summarize the current evidence and to make recommendations for diagnosis and classification of placenta previa and for managing the care of women with this diagnosis.

OPTIONS

To manage in hospital or as an outpatient and to perform a cesarean delivery preterm or at term or to allow a trial of labour when a diagnosis of placenta previa or a low-lying placenta is suspected or confirmed.

OUTCOMES

Prolonged hospitalization, preterm birth, rate of cesarean delivery, maternal morbidity and mortality, and postnatal morbidity and mortality.

INTENDED USERS

Family physicians, obstetricians, midwives, and other maternal care providers.

TARGET POPULATION

Pregnant women with placenta previa or low-lying placenta.

EVIDENCE

Medline, PubMed, Embase, and the Cochrane Library were searched from inception to October 2018. Medical Subject Heading (MeSH) terms and key words related to pregnancy, placenta previa, low-lying placenta, antepartum hemorrhage, short cervical length, preterm labour, and cesarean. This document represents an abstraction of the evidence rather than a methodological review.

VALIDATION METHODS

This guideline has been reviewed by the Maternal-Fetal Medicine and Diagnostic Imaging committees of the Society of Obstetricians and Gynaecologists of Canada (SOGC) and approved by the SOGC Board of Directors.

BENEFITS, HARMS, AND/OR COSTS

Women with placenta previa or low-lying placenta are at increased risk of maternal, fetal and postnatal adverse outcomes that include a potentially incorrect diagnosis and possibly unnecessary hospitalization, restriction of activities, early delivery, or cesarean delivery. Optimization of diagnosis and management protocols has potential to improve maternal, fetal and postnatal outcomes.

SUMMARY STATEMENTS (GRADE RATINGS IN PARENTHESES)

RECOMMENDATIONS (GRADE RATINGS IN PARENTHESES).

Maternal risk factors associated with persistent placenta previa

INTRODUCTION

Maternal risk factors associated with placenta previa are well documented in the literature. However, there are limited studies identifying maternal characteristics associated with the persistence of placenta previa. The objective of the study was to determine maternal characteristics associated with the persistent placenta previa.

METHODS

A retrospective cohort study was conducted in which 705 pregnant women diagnosed with low-lying placenta or placenta previa between 17 and 24 weeks gestation were identified from a single institution between 2003 and 2017. The primary outcome included persistent placenta previa (i.e., persistent placental tissue within 2 cm of the internal os) at or after 36 weeks 0 days. Those with abnormal placentation (e.g., vasa previa, placenta accreta) or delivery prior to 36 weeks 0 days were excluded. Multivariable logistic regression modeling was utilized to determine significant maternal characteristics associated with persistent placenta previa among women diagnosed with either placenta previa or low-lying placenta.

RESULTS

Women with a prior cesarean delivery were seven times more likely to have persistent placenta previa (odds ratio, 7.0, 95% confidence interval, 3.7-13.1). A history of intrauterine curettage or evacuation in the setting of placenta previa increases the likelihood of persistent placenta previa almost 3-fold (odds ratio, 2.5, 95% confidence interval, 1.3-5.0).

DISCUSSION

To date, our study is the largest, retrospective cohort study assessing maternal risk factors associated with persistent placenta previa; and is the first to detect a statistically significant correlation between a history of intrauterine surgeries and persistent placenta previa.

Diagnosis and management of placenta previa and low placental implantation

Objective: To evaluate the migration of low-placental implantation (LPI) during the third trimester of pregnancy and its effect on delivery and post-partum hemorrhage.Methods: We conducted a retrospective study at a level 3 maternity center including all cases of placenta previa (PP) and LPI between 1998 and 2014. The distance (d) between cervical internal os (CIO) and placental edge (PE) were measured by vaginal ultrasonography in the third trimester of pregnancy at 32 and 3 weeks after. We analyzed CIO-PE distance, volume of post-partum hemorrhage, delivery decision, and mode of delivery using Kruskall-Wallis test.Results: In total, 319 patients presented with PP or LPI. All complete PP (121) and 90.6% (58 of 64) of the placentas less than 1 cm from the CIO did not migrate. Among the 138 placentas with an initial CIO-PE d greater than 1 cm, only 17 (12.3%) did not migrate above 2 cm. The patients for whom the decision to perform a cesarean section (C-section) was retained and realized had a CIO-PE d significantly lower than those who delivered vaginally (p < .001). The patients who delivered by C-section had a lower CIO-PE d when an emergency C-section was performed, specifically for hemorrhage (p < .001). The mean volume of hemorrhage was significantly higher for patients with a CIO-PE d less than 2 cm.Conclusion: Complete PP and the majority of the placentas less than 1 cm from the CIO did not migrate. Above 1 cm, the majority of the placentas migrated three to four weeks later. For the placentas less than 1 cm from the CIO, a significant risk of hemorrhage at delivery was observed. Thus, prophylactic cesarean section is required for CIO-PE distances <1 cm. For distances between 1 and 2 cm, the volume of blood loss tends to be more important than for distances >3 cm without statistical significance. A vaginal delivery could be tried after information of patients.

Striking Multiple Primary Tumors that underwent Whipple Procedure due to Periampullary Carcinoma: An Analysis of 21 Cases

Introduction

The term multiple primary tumor (MPT) is used to describe cases where two or more primary tumors show no histopathological similarities in between. Multiple primary tumor cases have begun to increase in recent years as a result of the increase in life expectancy because of the increase in life standards and progress in diagnostic methods. In this study, MPT cases with periampullary tumors that underwent Whipple procedure were discussed in the light of literature data.

Materials and methods

The patient files of 223 cases with periampullary tumors that underwent Whipple procedure in our hospital during the last 6 years were examined retrospectively. More than one primary tumor was detected in 21 patients.

Results

Periampullary carcinomas were detected as a second primary tumor in 18 patients. First primary tumor was periampullary carcinoma in 3 patients that underwent Whipple procedure. After the Whipple procedure, 5 patients died due to early complications in the first 30 days and 6 patients died due to metastases and additional problems that developed during follow-up.

Discussion

The incidence of MPT has been reported as 0.7 to 14.5% in the literature. Most of them are multiple primary case presentations. In patient management, it is recommended that each tumor should be evaluated independently of its own characteristics, and treatment and follow-up should be planned accordingly.

Conclusion

The MPT cases are increasing. The possibility of MPT as well as metastasis should be kept in mind during the evaluation of tumor foci seen during diagnosis and follow-up of patients. The characteristics of each tumor, survival, and prognosis should be evaluated separately and the most appropriate treatment should be offered to the patient. It is recommended that synchronic primary tumors which are considered to be surgically resectable without metastasis should be removed in the same session.How to cite this article: Dilek ON, Ozsay O, Karaisli S, Gür EÖ, Er A, Haciyanli SG, Kar H, Dilek FH. Striking Multiple Primary Tumors that underwent Whipple Procedure due to Periampullary Carcinoma: An Analysis of 21 Cases. Euroasian J Hepato-Gastroenterol 2018;8(1):1-5.

Primary Gastric Lymphoma: Clinicopathological Profile

Introduction

Gastrointestinal tract (GIT) is the most common site of involvement of extranodal non-Hodgkin’s lymphoma (NHL). There is regional variation in anatomical distribution of extranodal NHL, stomach being the most common site followed by small intestine. Primary gastric lymphoma (PGL) predominantly involves the antrum and corpus of the stomach. It arises from mucosa-associated lymphoid tissue (MALT) and is of B-cell lineage and often associated with Helicobacter pylori infection. Primary gastric lymphoma often presents with nonspecific symptoms. The present study was undertaken to ascertain the clinicopathological characteristics of PGL at a tertiary care center in South India.

Materials and methods

It is a retrospective study from 2006 to 2016. Patient’s data were obtained from institutional medical records. The histopathology slides were reviewed. The relevant immunohistochemistry (IHC) markers done were leukocyte common antigen (LCA), CD3, CD20, CD79a, CD10, Bcl-2, Bcl-6, CD5, Cyclin D1, CD138, and Ki-67. Correlating with the immunoprofile, further subtyping was done.

Results

A total of 405 patients of NHL were seen during the study period, out of which 43 patients were PGL. There were 32 males and 11 females, with M:F of 2.9:1. The mean age at diagnosis was 58 years. Abdominal pain and new-onset dyspepsia were the commonly observed presenting symptoms. The common site of involvement was antrum (20). Diffuse large B-cell lymphoma (DLBCL) was the most common histological subtype. Helicobacter pylori infection was seen in 18 (41%) patients. Majority of the patients were in stages II and III.

Conclusion

In our study, the initial presentation of PGL was with nonspecific symptoms like abdominal pain and new-onset dyspepsia. High degree of suspicion of such symptoms and biopsy of all suspicious lesions is essential for early detection. Diffuse large B-cell lymphoma was the most common histological subtype seen in our study.

How to cite this article: Malipatel R, Patil M, Rout P, Correa M, Devarbhavi H. Primary Gastric Lymphoma: Clinicopathological Profile. Euroasian J Hepato-Gastroenterol 2018;8(1):6-10.

Measuring leading placental edge to internal cervical os: Transabdominal versus transvaginal approach

We aimed to compare the value of transabdominal (TA) and transvaginal (TV) approaches for assessing the risk of a low-lying placenta. This involved a comparison of TA and TV measurements between the leading placental edge and the internal cervical os. We also assessed the intra-/interobserver variation for these measurements and the efficacy of TA measures in screening for a low placenta.

METHODOLOGY

Transabdominal and TV measurements of the leading placental edge to the internal cervical os were performed on 369 consecutive pregnancies of 16-41 weeks' gestation. The difference (TA-TV) from the mean was calculated and plotted against gestational age. Bland-Altman plots and paired t-tests were used to look at the differences in TA/TV measurement. Screening performance of a transabdominal approach was compared to a transvaginal 'gold standard'. Nonparametric methods were used to calculate the area under the receiver operator characteristics (ROC) curve. Intra-/interobserver variations were also calculated.

RESULTS

Of the pregnancies, 278 had a leading placental edge that was visible with the TV approach. Differences (TA-TV) ranged from -50 mm to +57 mm. Bland-Altman plot shows that TA measurements overestimated the distance compared with the TV measurements; the average difference in measurement was 12.0 mm (95% confidence interval 9.9-14.1). The sensitivity, specificity and negative predictive values of a TA approach were 18.2%, 97.5% and 87.2%, respectively. The receiver operator characteristics area between gestational weeks 16-23 was 0.81 (95% CI: 0.76-0.86).

CONCLUSION

The TA approach has a low sensitivity for detecting a low-lying placenta as choosing a TA cut-off with sensitivity >90% will decrease the specificity to 50%.

Relationship between placenta location and resolution of second trimester placenta previa

This prospective study was conducted to assess the rate of resolution of second trimester placenta previa in women with anterior placenta and posterior placenta, and that in women with and without previous cesarean section. In this study, placenta previa was defined as a placenta lying within 20 mm of the internal cervical os or overlapping it. We recruited 183 women diagnosed with previa between 20⁺⁰ weeks and 25⁺⁶ weeks. They were grouped according to their placenta location (anterior or posterior) and history of cesarean section. Comparative analysis was performed on demographic data, resolution rate of previa and pregnancy outcomes between anterior group and posterior group, and on those between cesarean section group and non-cesarean section group. Women with an anterior placenta tended to be advanced in parity (P=0.040) and have increased number of dilatation and curettage (P=0.044). The women in cesarean section group were significantly older (P=0.000) and had more parity (P=0.000), gravidity (P=0.000), and dilatation and curettage (P=0.048) than in non-cesarean section group. Resolution of previa at delivery occurred in 87.43% women in this study. Women with a posterior placenta had a higher rate of resolution (P=0.030), while history of cesarean section made no difference. Gestational age at resolution was earlier in posterior group (P=0.002) and non-cesarean section group (P=0.008) than in anterior group and cesarean section group correspondingly. Placenta location and prior cesarean section did not influence obstetric outcomes and neonatal outcomes. This study indicates that it is more likely to have subsequent resolution of the previa when the placenta is posteriorly located for women who are diagnosed with placenta previa in the second trimester.

Using ultrasound in the clinical management of placental implantation abnormalities

Placental implantation abnormalities, including placenta previa, placenta accreta, vasa previa, and velamentous cord insertion, can have catastrophic consequences for both mother and fetus, especially as pregnancy progresses to term. In these situations, current recommendations for management usually call for an indicated preterm delivery even in asymptomatic patients. However, the recommended gestational age(s) for delivery in asymptomatic patients are empirically determined without consideration of the recent literature regarding the usefulness of specific ultrasound findings to help individualize management. The purpose of this article is to propose literature-supported guidelines to the current opinion-based management of asymptomatic patients with placental implantation abnormalities based on relevant and specific ultrasound findings such as cervical length, distance between the internal cervical os and placenta, and placental edge thickness.

Proposal of a new parameter for diagnosing a low-lying placenta in the third trimester: The distance between the external os and placental edge

OBJECTIVE

To validate a new parameter of the distance between the external os (EO) and placental edge (PE) to diagnose a low-lying placenta in the third trimester.

MATERIALS AND METHODS

The study participants included 94 uncomplicated singleton pregnant women with cephalic presentation. These women were cared for in our hospital in 1998-2011, with a posterior low-lying placenta, which was diagnosed as the distance between the internal os (IO) and a PE of 0-3.0 cm at 34-36 weeks' gestation. Measurements of cervical length (CL) and the distances of IO-PE and EO-PE were performed using transvaginal ultrasonography at least twice at 28-30 weeks, 31-33 weeks, and 34-36 weeks. Changes in CL, and the IO-PE and EO-PE distances were analyzed.

RESULTS

CL and the IO-PE and EO-PE distances did not change prior to 31-33 weeks. CL was shortened and the IO-PE distance was increased after 31-33 weeks (p = 0.0001), but the EO-PE distance was unchanged.

CONCLUSION

The EO-PE distance is a promising parameter for diagnosis of low-lying placenta in the third trimester up to 36 weeks' gestation.

Outcomes of pregnancies with a low-lying placenta diagnosed on second-trimester sonography

OBJECTIVES

The purpose of this study was to determine how often a low-lying placenta, defined as a placenta ending within 2 cm of the internal cervical os but not covering it, diagnosed sonographically in the second trimester resolves before delivery.

METHODS

After Institutional Review Board approval was obtained, 1416 pregnancies with a sonographically diagnosed low-lying placenta between 16 and 24 weeks' gestation were identified from our ultrasound database over a 5-year period. We reviewed medical records to determine the gestational age at which the low-lying placenta was first diagnosed, the gestational age at which the placenta was no longer sonographically low lying or covering the cervix, and, of those whose placentas that never cleared the internal cervical os sonographically, how many went on to cesarean delivery as a result of placental location.

RESULTS

In total, 1220 of 1240 low-lying placentas (98.4%) that had sonographic follow up resolved to no previa before delivery; 89.9% of placentas cleared the cervix by 32 weeks, and 95.9% cleared by 36 weeks. Twenty patients (1.6%) had persistent sonographic placenta previa or a low-lying placenta at or near term, including 5 complete previas, 7 marginal previas, 5 low-lying placentas, and 3 vasa previas; all had cesarean deliveries.

CONCLUSIONS

A low-lying placenta sonographically diagnosed in the second trimester typically resolves by the mid third trimester. Only rarely (1.6% of the time) does it persist to term or near term. Follow-up sonography is warranted to diagnose persistent placenta previa or vasa previa, a complication of a low-lying placenta.

Does the presence of a cesarean section scar influence the site of placental implantation and subsequent migration in future pregnancies: a prospective case-control study

OBJECTIVES

To describe placental location in the first trimester of pregnancy and subsequent placental migration in women with and without a history of previous cesarean delivery.

METHODS

In this prospective case-control study, placental location was defined according to five anatomical sites in relation to the endometrial cavity. Placental localization was carried out by transabdominal ultrasound between 11 and 14 weeks' gestation. We recruited 738 women who had undergone one or more previous cesarean sections (CS) and 1856 patients without previous cesarean delivery. Comparative analysis was performed of placental location between the two groups, and to assess placental migration of those classified as being low lying at 20 and 32 weeks' gestation.

RESULTS

There were significant differences in placental location between the two groups. In the CS group there were significantly more posterior and fewer fundal placentae than in the control group (47.2 vs 31.5% and 4.7 vs 15.5%, respectively). The number of previous cesarean deliveries did not have a significant effect on placental location. There was no significant difference in the incidence of anterior low-lying placenta between groups (1.5 vs 0.9%). Placental migration of the low-lying subtypes was similar in both groups (62 vs 64%).

CONCLUSION

The presence of CS scars in the uterus are associated with an increase in the number of posterior placentae and a reduced number that implant in the fundus of the cavity. Migration of a low-lying placenta is independent of the presence of a CS scar in the uterus.

Resolution of complete placenta previa: does prior cesarean delivery matter?

OBJECTIVES

The purpose of this study was to prospectively assess the rate of resolution of complete placenta previa diagnosed at second-trimester sonography in patients with and without previous cesarean delivery.

METHODS

This prospective study evaluated patients at 3 institutions with complete placenta previa diagnosed at second-trimester screening sonography. All patients were followed with sonography every 4 to 6 weeks until either resolution of the previa or delivery occurred. Patients with persistent/nonresolving complete placenta previa underwent cesarean delivery.

RESULTS

A total of 67 patients were enrolled in the study; 18 patients had a prior cesarean delivery. Resolution of placenta previa occurred in 11 of 18 patients (61%) with a prior cesarean delivery, whereas 44 of 49 patients (90%) without a prior cesarean delivery had resolution of placenta previa (P = .012, Fisher exact test). Placental location per se (anterior or posterior) was not associated with resolution of placenta previa (P = .22). Complete placenta previa persisted to delivery in 5 of 9 patients (56%) with a prior cesarean delivery and an anterior placental location.

CONCLUSIONS

This prospective study indicates that patients with a prior cesarean delivery and complete placenta previa diagnosed at second-trimester sonography are less likely to have subsequent resolution of the previa when compared to those without a history of cesarean delivery.

Placenta and Transvaginal Sonography

In recent years, transvaginal evaluation of the placenta has completely changed the way obstetricians need to perceive and assess a low-lying placenta. Additionally, the number of negative ultrasound examinations in morbid placental adherence has reduced. This article presents the evidence on the safety and accuracy of transvaginal placental evaluation and goes on to discuss the manner in which transvaginal findings should alter clinical protocols to optimize maternal and fetal outcomes. It also answers a very pertinent clinical question: How low is low?

How to cite this article

Khurana A. Placenta and Transvaginal Sonography. Donald School J Ultrasound Obstet Gynecol 2012;6(4):391-397.

Systematic labeling of twin pregnancies on ultrasound

OBJECTIVE

Correct labeling of twin fetuses is needed for consistency in assigning and interpreting longitudinal scan and prenatal screening/diagnostic results. The aim of this study was to describe a standard method of twin labeling in the first trimester of pregnancy and to assess the robustness of such a technique in predicting the presenting twin in subsequent scans and at delivery.

METHODS

This was a retrospective first-trimester study of all twin pregnancies assessed by ultrasonography at our center between 2000 and 2010. The fetus contained in the gestational sac closer to the maternal cervix was designated as Twin 1 and the relative orientation of the fetuses to each other was then defined as either lateral (left/right) or vertical (top/bottom). In discordant-sex twins, their sex and presenting order on the final scan prior to delivery were documented and compared with the sex and birth order at delivery.

RESULTS

A total of 416 twin pregnancies were seen during the study period. At the 11-14-week scan 90.9% of twins were in lateral orientation while the remainder were oriented vertically. None of the vertically oriented twin pairs but 32 (8.5%) of the laterally oriented twin pairs changed their presenting order between the first and the last ultrasound scan prior to delivery. There were 108 discordant-sex twins scanned in the third trimester, of which the birth order changed in 20.3% that were delivered by Cesarean section and in 5.9% of those delivered vaginally.

CONCLUSION

The study demonstrates that antenatal labeling of twins according to laterality or vertical orientation is reliable. The technique ensures continuity of biometric assessment from serial scans at each visit, and as such should be adopted as the preferred method of twin labeling. Furthermore, the use of orientation for antenatal labeling of twins rather than assignment of a number based on proximity to the cervix, precludes any misconception regarding which twin will be born first and ensures that parents and pediatricians are aware of the significant likelihood of a peripartum switch.

Effect of a low-lying placenta on delivery outcome

OBJECTIVES

To evaluate delivery outcome in pregnancies with a low-lying placenta (within 2 cm of, but not covering, the internal os) that had been identified within 4 weeks of delivery. We examined the likelihood of a vaginal delivery and investigated the clinical significance of the placental edge to internal os measurement.

METHODS

A retrospective chart review was performed for singleton pregnancies delivering in the third trimester with a low-lying placenta identified within 4 weeks of delivery. Outcome variables included type of delivery, maternal and neonatal hemoglobin levels, and umbilical artery pH levels.

RESULTS

Eighty-six patients met the study criteria of a low-lying placenta identified within 4 weeks of delivery. Forty-five of these patients were allowed to labor and, of these, 29 (64.4%) delivered vaginally. The vaginal delivery rate was 76.5% in patients with a placenta to cervical os distance of 1-2 cm, significantly greater than the rate of 27.3% in patients in whom the placenta was within 1 cm of the cervix (P = 0.0085). A maternal hemoglobin level below 8.0 g/dL was the most common morbidity associated with low-lying placenta. Analysis of morbidity observed did not clearly favor either elective Cesarean delivery or attempted vaginal delivery.

CONCLUSIONS

In this retrospective study, most laboring patients with a low-lying placenta were able to have a vaginal delivery with limited morbidity. The likelihood of a vaginal delivery was greater with increased placenta to cervical os distance. Further studies are needed to determine the clinical significance of the placenta to cervical os distance and the interval from scan to delivery.

Cervical length and risk of antepartum bleeding in women with complete placenta previa

OBJECTIVE

To evaluate if cervical length predicts prepartum bleeding and emergency Cesarean section in cases of placenta previa.

METHODS

Between September 2005 and September 2007, cervical length was measured by transvaginal ultrasound in women with complete placenta previa persisting into the third trimester of pregnancy. A complete follow-up of pregnancy was obtained in all cases.

RESULTS

Overall, 59 women were included in the study group. The mean +/- SD gestational age at ultrasound was 30.7 +/- 2.7 weeks and the cervical length was 36.9 +/- 8.8 mm. Cesarean delivery was performed in all cases, at a mean gestational age of 34.7 +/- 2.3 weeks. Twenty-nine (49.1%) of the women presented prepartum bleeding and 12 (20.3%) required an emergency Cesarean section prior to 34 completed weeks due to massive hemorrhage. Cervical length did not differ significantly between cases with and those without prepartum bleeding (35.3 +/- 9.3 mm vs. 38.4 +/- 8.2 mm; P = 0.18), but was significantly shorter among patients who underwent emergency Cesarean section < 34 weeks due to massive hemorrhage compared with patients who underwent elective Cesarean section (29.4 +/- 5.7 mm vs. 38.8 +/- 8.5 mm; P = 0.0006).

CONCLUSIONS

Transvaginal sonographic cervical length predicts the risk of emergency Cesarean section < 34 weeks in women with complete placenta previa.

Ultrasound of the placenta: a systematic approach. Part I: Imaging

Diagnostic ultrasound has been in use in clinical obstetrics for close to half-a-century. However, in the literature, examination of the placenta appears to be treated with less attention than the fetus or the pregnant uterus. This is somewhat unexpected, given the obvious major functions this organ performs during the entire pregnancy. Examination of the placenta plays a foremost role in the assessment of normal and abnormal pregnancies. A methodical sonographic evaluation of the placenta should include: location, visual estimation of the size (and, if appearing abnormal, measurement of thickness and/or volume), implantation, morphology, anatomy, as well as a search for anomalies, such as additional lobes and tumors. Additional assessment for multiple gestations consists of examining the intervening membranes (if present). The current review considers the various placental characteristics, as they can be evaluated by ultrasound, and the clinical significance of abnormalities of these features. Numerous and varied pathologies of the placenta can be detected by routine ultrasound. It is incumbent on the clinician performing obstetrical ultrasound to examine the placenta in details and in a methodical fashion because of the far reaching clinical significance and potentially avoidable severe consequences of many of these abnormalities.

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

PURPOSE

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).

METHODS

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.

RESULTS

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.

CONCLUSION

Anterior PP and LLP may migrate more often and faster than posterior PP. Our results may be useful for planning of prenatal management and counseling patients with PP and LLP.

A sonographic assessment of different patterns of placenta previa "migration" in the third trimester of pregnancy

OBJECTIVE

The purpose of this study was to compare the rates and patterns of placental "migration" with the mode of fetal and placental delivery and the incidence of peripartum complications.

METHODS

This was a retrospective study of 163 cases of placenta previa diagnosed by transvaginal sonography at 28 weeks' gestation that were followed serially by sonography. The patients were stratified into 3 groups depending on the placenta-to-internal cervical os distance: (1) an overlap of 0.0 cm or greater over the cervical os, (2) 0.1 to 2.9 cm, and (3) 3.0 cm or greater. The mean rate of placental migration (millimeters per week) was obtained at 28 to 32 and 32 to 36 weeks' gestation. A pattern of placental migration was classified as one with acceleration or deceleration of the placental migration in the late third trimester based on a comparison between the migration rates at 28 to 32 and 32 to 36 weeks' gestation.

RESULTS

At the time of delivery, 22, 29, and 112 patients were included in groups 1, 2, and 3, respectively. The rates of placental migration correlated with the final placental distance from the internal cervical os (0.1 to 4.1 mm/wk for groups 1 and 3, respectively). Significantly higher rates of interventional cesarean delivery (CD) (P=.0002), elective CD (P=.0254), manual placenta removal (P=.0419), and placenta accreta (P=.0039), but not CD for indications other than placenta previa (P=.0752), were associated with a placental distance of less than 2.0 cm away from the cervix and a deceleration pattern of placental migration. In contrast, vaginal delivery was significantly associated with a placental distance of 2.0 cm or greater away from the cervix and an acceleration pattern of placental migration (P=.0034).

CONCLUSIONS

A final placental distance of less than 2.0 cm from the internal cervical os and a deceleration pattern of placental migration were significantly associated with an interventional CD and a higher rate of peripartum complications.

Recent advances in the management of placenta previa

PURPOSE OF REVIEW

Despite the widespread and routine use of ultrasound to make the diagnosis of placenta previa, evidence-based classification and management strategies have failed to evolve over the years. The purpose of this review is to present the current evidence supporting the screening, diagnosis and management of placenta previa.

RECENT FINDINGS

The prevalence of placenta previa is significantly overestimated due to the practice of routine mid-pregnancy scan, and many women currently undergo a repeat scan in late pregnancy for placental localization. Recent reports support limiting third-trimester scans to only those cases where the placental edge either reaches or overlaps the internal cervical os at 20-23 weeks of pregnancy. In some cases of mid-trimester placenta previa, the placental edge is more likely to "migrate" than others, and it appears that ultrasound may be useful to predict this process. At term, women with placental edge within 2 cm of the internal cervical os require a Caesarean section for delivery, whereas an attempt at vaginal birth is appropriate if this distance is more that 2 cm. Ultrasound also has a role in the diagnosis and management of both vasa previa and placenta accreta.

SUMMARY

This review addresses screening for placenta previa. A simple and pragmatic ultrasound classification of placenta previa and low-lying placenta is proposed. Caesarean section is recommended for delivery in cases of placenta previa. Women with a low-lying placenta have at least 60% chance of a vaginal birth, but should be monitored for post-partum haemorrhage. Vasa previa is a rare complication but antenatal diagnosis is possible. It should particularly be suspected in in-vitro fertilization conceptions, and where the placental edge covers the os in mid-pregnancy but recedes later on. Prenatal diagnosis of placenta accreta should be based on the placental lacunae signs rather than the absence of retro-placental clear space.

US of abnormal uterine bleeding

Any significant deviation from a woman's established menstrual pattern may be considered abnormal uterine bleeding, and several factors direct evaluation of a patient with such bleeding. Premenopausal disorders that are well evaluated with ultrasound (US) include endometriosis, adenomyosis, and leiomyomas. A positive pregnancy test in a woman of childbearing age prompts a search for an intrauterine pregnancy. Possible complications that may contribute to bleeding include ectopic pregnancy; placental factors including position, trauma, and infection; gestational trophoblastic disease; preterm labor; and postpartum complications. Atrophic changes, hormonal status, and carcinoma are considerations in the postmenopausal patient with abnormal uterine bleeding. Foreign bodies, trauma, infection, polyps, and iatrogenic causes can be observed in all groups. Differential diagnoses for abnormal uterine bleeding in premenopausal, pregnant, and postmenopausal patients are well evaluated with US, and US techniques have greatly facilitated evaluation of pelvic disease. Urgent and emergent conditions such as ectopic pregnancy, placenta previa, and preterm labor are readily identifiable.

Transvaginal ultrasonography in predicting placenta previa at delivery: a longitudinal study

OBJECTIVES

To determine the extent of overlapping of the internal cervical os by the lower placental edge at 11-14 weeks' gestation which best predicts placenta previa at term.

PATIENTS AND METHODS

This was a prospective study initially involving 381 singleton pregnancies with a live fetus at 11-14 weeks attending for routine antenatal care. The distance between the lower placental edge and the internal cervical os was longitudinally evaluated by transvaginal ultrasound examination at 11-14 weeks', 20-24 weeks', and 30-34 weeks' gestation. The first 203 cases were selected at random (first phase) and after this period only cases with the lower placental edge reaching and/or overlapping the internal cervical os were followed up (n = 170, second phase). Thus a total of 373 cases were analyzed, 351 of whom were examined in all three trimesters. Multiple regression analysis was used to estimate the probability of predicting placenta previa at term using the overlap of the lower placental edge over the internal cervical os in the first trimester of pregnancy.

RESULTS

A change in the relative position of the placenta (placental migration) was observed in all 351 cases examined in the three trimesters of pregnancy. In the general population, represented by the 203 cases (first phase), the incidence of placenta previa at 11-14 weeks' gestation was 42.3% (86/203), at 20-24 weeks' 3.9% (8/203) and at term 1.9% (4/203). A total of 18 cases of placenta previa and 17 cases of marginal placenta were observed at term. It was estimated that when the lower placental edge overlaps the internal cervical os by 23 mm at 11-14 weeks the probability of placenta previa at term is 8% with a sensitivity of 83.3% and specificity of 86.1%.

CONCLUSION

The present study establishes the probability of placenta previa at term depending on the relationship of the lower placental edge to the internal cervical os at 11-14 weeks.