Second trimester placental location as a predictor of an adverse pregnancy outcome

A Resolved Placenta Previa Is Still Associated with Postpartum Hemorrhage

OBJECTIVE

Our objective was to determine whether resolution of a low-lying placenta or placenta previa is associated with postpartum hemorrhage (PPH).

STUDY DESIGN

This is a retrospective, matched-control cohort study of women who underwent transvaginal sonography during fetal anatomic survey between 18 and 24 weeks of gestation at the University of Pennsylvania from January 2017 to May 2019. Exposure was defined as low-lying placenta (≤1 cm from the internal cervical os) or placenta previa (covering the os) at anatomic survey that was found to be resolved by transvaginal ultrasound in the third trimester. For each exposure, we identified a control patient whose placenta was > 1 cm from internal os at anatomic survey performed on the same day. The primary outcome was PPH at delivery, defined as estimated blood loss ≥ 1,000 mL.

RESULTS

A total of 450 women were included (225/group). The exposed group of resolved placental previa included 85.0% with resolved low-lying placenta and 15.0% with resolved previa. The rate of PPH was significantly higher in the exposed group versus controls (9.8% vs. 4.4%, p = 0.03). Women with resolved previa were 2.5 times more likely to experience PPH than controls (adjusted odds ratio = 2.58, 95% confidence interval: 1.17-5.69), even when controlling for parity, prior cesarean, and delivery mode. Women with resolved previa were also more likely to present to triage with bleeding (16.4% vs. 8.0%, p = 0.006), receive antenatal corticosteroids, (9.3% vs. 3.1%, p = 0.006), and receive intravenous iron postpartum (7.6% vs. 3.1%, p = 0.04).

CONCLUSION

Our data demonstrate that women with a resolved low-lying placenta or placenta previa remain at significantly increased risk of bleeding-related complications in pregnancy and during delivery when compared with those who never had a previa. Clinicians should consider this association when counseling patients and performing hemorrhage risk stratification.

KEY POINTS

· Women with resolved previa or low-lying placenta were 2.5 times more likely to experience PPH.. · Women with resolved previa or low-lying placenta were more likely to be induced for bleeding.. · Resolved previa or low-lying placenta is still associated with adverse hemorrhage-related outcomes..

Cumulative Prenatal Risk Factors and Developmental Coordination Disorder in Young Children

OBJECTIVES

To examine the effect of cumulative prenatal risk factors (RFs) on the presence of Developmental Coordination Disorder (DCD) in young children.

METHODS

Participants (N = 589, 338 boys, Mage = 4.5 ± 0.5 years) were from a larger cohort study, the Coordination and Activity Tracking in Children (CATCH). Motor coordination was assessed using the Movement Assessment Battery for Children- 2nd Edition. Children were classified as at risk for DCD (DCDr) based on European Academy of Childhood Disability guidelines. RFs were obtained through a parent-completed survey. A multiple logistic regression was conducted to examine the effect of the RFs on DCD.

RESULTS

Results showed that the odds of a child having DCDr are significantly higher with a greater total number of prenatal RFs, after adjustment for mother's age at child's birth, child's sex, child's age, marital status and total annual household income (OR = 1.48, p < 0.01).

CONCLUSIONS

These findings warrant further investigation into the cumulative impact of multiple prenatal RFs and whether specific combinations of RFs might be more strongly linked to DCD than others. These results provide additional insight into possible causes and prevention of DCD.

A Multicenter, Retrospective Comparison Study of Pregnancy Outcomes According to Placental Location in Placenta Previa

Background: We investigated the association between placental location and pregnancy outcomes in placenta previa. Methods: This multi-center retrospective study enrolled 781 women who delivered between May 1999 and February 2020. We divided the dataset into anterior (n = 209) and posterior (n = 572) groups and compared the baseline characteristics and obstetric and neonatal outcomes. The adverse obstetric outcomes associated with placenta location were evaluated using a multivariate logistic analysis. Results: Gestational age at delivery in the anterior group (253.0 ± 21.6) was significantly lower than that in the posterior group (257.6 ± 19.1) (p = 0.008). The anterior group showed significantly higher parity, rates of previous cesarean section, non-vertex fetal positions, admissions for bleeding, emergency cesarean sections, transfusions, estimated blood loss, and combined placenta accrete spectrum (p < 0.05). In the multivariate analysis, the anterior group had higher rates of transfusion (OR 2.23; 95% CI 1.50-3.30), placenta accreta spectrum (OR 2.16; 95% CI 1.21-3.97), and non-vertex fetal positions (OR 2.47; 95% CI 1.09-5.88). Conclusions: These findings suggest that more caution is required in the treatment of patients with anterior placenta previa. Therefore, if placenta previa is diagnosed prenatally, it is important to determine the location of the body and prepare for massive bleeding in the anterior group.

A Cross-Sectional Study to Evaluate the Impact of Placental Location on Maternal and Fetal Outcomes

Background The human placenta is a critical organ for facilitating nutrient uptake, waste elimination, and gaseous exchange between the mother and the fetus. In the placenta, there are two circulations, namely, maternal and fetal. The blood supply of the placenta is not uniformly distributed as the maternal circulation, determined by uterine blood supply, depends on the implantation site. The uterine blood supply plays a significant role in placental blood flow and pregnancy success. Hence, abnormalities in the placental implantation may affect the placenta's blood supply, leading to adverse maternal and fetal outcomes. This study aims to examine the relationship between placental location and maternofetal outcomes. Methodology This cross-sectional study was conducted in the Department of Obstetrics & Gynaecology at Bijapur Lingayat District Educational Association (Deemed to be University), Shri B. M. Patil Medical College, Hospital and Research Centre, Vijayapura, from January 2021 to April 2022. A total of 1,301 patients were included in this study. Results There was a positive and significant association between fundal implantation and severe preeclampsia and premature rupture of membranes. There was a positive and significant association between left lateral implantation and severe preeclampsia. The histopathological changes seen in the histopathological report of the fetal surface of the placenta also had a positive and significant association with the fundal location of the placenta. Conclusions This study suggests that fundal left lateral placentation leads to abnormal results. Such patients can be considered high risk and should be given meticulous antenatal care, depending on placental location at the 28-week ultrasonography.

The impact of lateral placenta on preeclampsia and small for gestational age neonates: a systematic review and meta-analysis

OBJECTIVES

We conducted a systematic review and meta-analysis to quantitatively summarize the present data on the association of prenatally identified lateral placenta in singleton pregnancies with small for gestational age (SGA) neonates, preeclampsia and other perinatal outcomes.

METHODS

From inception to November 2021, we searched PubMed/Medline, Scopus and The Cochrane Library for papers comparing the risk of SGA and preeclampsia, as well as other perinatal outcomes in singleton pregnancies with a prenatally identified lateral placenta to those with non-lateral placentas. The revised Newcastle-Ottawa Scale was used to evaluate the quality of eligible papers. The I² test was employed to evaluate the heterogeneity of outcomes among the studies. To investigate the possibility of publication bias, funnel plots were constructed. Prospero RN: CRD42021251590.

RESULTS

The search yielded 5,420 articles, of which 16 were chosen, comprising of 15 cohort studies and one case control study with a total of 4,947 cases of lateral and 96,035 of non-lateral placenta (controls) reported. SGA neonates were more likely to be delivered in cases with a lateral placenta (OR: 1.74; 95% CI: 1.54-1.96; p<0.00001; I²=47%). Likewise, placental laterality was linked to a higher risk of fetal growth restriction (OR: 2.18; 95% CI: 1.54-3.06; p<0.00001; I2=0%), hypertensive disorders of pregnancy (OR: 2.39; 95% CI: 1.65-3.51; p=0.0001; I²=80%), preeclampsia (OR: 2.92; 95% CI: 1.92-4.44; p<0.0001; I²=82%) and preterm delivery (OR: 1.65; 95% CI: 1.46-1.87; p<0.00001; I²=0%).

CONCLUSIONS

The prenatal diagnosis of a lateral placenta appears to be associated with a higher incidence of preeclampsia, fetal growth restriction, preterm delivery and SGA. This may prove useful in screening for these conditions at the second trimester anomaly scan.

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.

Association between placental location and neonatal outcomes in manual fundal pressure-assisted vaginal deliveries: A retrospective single-center study in Japan

AIM

Manual fundal pressure (MFP) is still used to assist vaginal deliveries during the second stage of labor in predominantly lower-middle income countries; however, there is insufficient evidence on the risk factors in MFP-assisted vaginal deliveries for adverse neonatal outcomes. The aim of the present study was to investigate the association between placental location and neonatal outcomes in MFP-assisted vaginal deliveries.

METHODS

The present study was a single-center retrospective cohort study in patients with all MFP-assisted vaginal singleton deliveries from January 2016 to December 2020. Placental location was divided into two categories: posterior-lateral and anterior-fundal. The primary outcome was a neonatal adverse composite including umbilical artery blood pH <7.2, Apgar score <7 at 5 min, neonatal intensive care unit admission and neonatal resuscitation. We used multivariable logistic regression models to investigate the association between placental location and neonatal outcomes.

RESULTS

We extracted 522 MFP-assisted deliveries among 5053 vaginal deliveries. The proportion of posterior-lateral and anterior-fundal placentation was 239 (45.8%) and 283 (54.2%), respectively. The crude prevalence of neonatal composite outcome in the anterior-fundal group was significantly higher than that in the posterior-lateral group (39.6% vs. 28.9%; p = 0.013). Multivariable logistic regression analysis found that the prevalence of neonatal adverse outcome in the anterior-fundal group was significantly higher compared with the posterior-lateral group (adjusted odds ratio, 1.52; 95% confidence interval, 1.04-2.23).

CONCLUSION

Anterior-fundal placentation was significantly associated with an increased risk of neonatal adverse outcomes compared to posterior-lateral placentation in MFP-assisted vaginal deliveries.

Placental location site and adverse antepartum pregnancy complications: a meta-analysis and review of the literature

PURPOSE

The purpose to the study was to determine the relationship, if any, between the placental location site and antepartum complications of pregnancy.

METHODS

A University research librarian conducted a comprehensive literature search using the search engines PubMed and Web of Science. The search terms were "placental location" AND "pregnancy complications" OR "perinatal complications. There were no limits put on the years of the search.

RESULTS

The search identified 110 articles. After reviewing all the abstracts, relevant full articles, and references of full articles, there were 22 articles identified specific to antepartum complications. Central + fundal locations compared to all lateral were associated with a lower risk of hypertension during pregnancy RR = 0.47, 95% CI: 0.31-0.71]. Central location compared to all lateral was also associated with lower risk of hypertension during pregnancy [RR = 0.39, 95% CI: 0.26-0.59]. Placenta locations in the lower uterine segment were associated with greater risk of antepartum hemorrhage (APH) [RR = 2.99, 95% CI: 1.16-7.75] compared to above the lower uterine segment. No differences were observed in placental locations and gestational diabetes (GDM), preterm prelabor rupture of membranes (PPROM), preterm delivery (PTD) or on a placental abruption.

CONCLUSION

Central and fundal location sites and central location alone decreased the risk of hypertension during pregnancy. Low uterine segment location sites increased the risk for APH. There were no effects of placenta location sites on the development of GDM, PPROM, PTD or abruption.

Considering intrauterine location in a model of fetal growth restriction after maternal titanium dioxide nanoparticle inhalation

Fetal growth restriction (FGR) is a condition with several underlying etiologies including gestational disease (e.g., preeclampsia, gestational diabetes) and xenobiotic exposure (e.g., environmental contaminants, pharmaceuticals, recreational drugs). Rodent models allow study of FGR pathogenesis. However, given the multiparous rodent pregnancy, fetal growth variability within uterine horns may arise. To ascertain whether intrauterine position is a determinant of fetal growth, we redesigned fetal weight analysis to include litter size and maternal weight. Our FGR model is produced by exposing pregnant Sprague Dawley rats to aerosolized titanium dioxide nanoparticles at 9.44 ± 0.26 mg/m3 on gestational day (GD) 4, GD 12 or GD 17 or 9.53 ± 1.01 mg/m3 between GD 4-GD 19. In this study fetal weight data was reorganized by intrauterine location [i.e., right/left uterine horn and ovarian/middle/vaginal position] and normalized by maternal weight and number of feti per uterine horn. A significant difference in fetal weight in the middle location in controls (0.061g ± 0.001 vs. 0.055g ± 0.002), GD 4 (0.033g ± 0.003 vs. 0.049g ± 0.004), and GD 17 (0.047g ± 0.002 vs. 0.038g ± 0.002) exposed animals was identified. Additionally, GD 4 exposure produced significantly smaller feti in the right uterine horn at the ovarian end (0.052g ± 0.003 vs. 0.029g ± 0.003) and middle of the right uterine horn (0.060g ± 0.001 vs. 0.033g ± 0.003). GD 17 exposure produced significantly smaller feti in the left uterine horn middle location (0.055g ± 0.002 vs. 0.033 ± 0.002). Placental weights were unaffected, and placental efficiency was reduced in the right uterine horn middle location after GD 17 exposure (5.74g ± 0.16 vs. 5.09g ± 0.14). These findings identified: 1) differences in fetal weight of controls between the right and left horns in the middle position, and 2) differential effects of single whole-body pulmonary exposure to titanium dioxide nanoparticles on fetal weight by position and window of maternal exposure. In conclusion, these results indicate that consideration for intrauterine position, maternal weight, and number of feti per horn provides a more sensitive assessment of FGR from rodent reproductive and developmental studies.

Lateral placentation and adverse perinatal outcomes

Lateral placentation may compromise placental perfusion, and we aimed to assess whether it impacts pregnancy outcomes. This single-center retrospective study included 1203 singleton pregnancies, categorized into two groups according to placental location. Women with lateral placenta had significantly higher risk of preterm birth <37 weeks (aOR 2.99) and <34 weeks (aOR 3.92), and gestational diabetes (aOR 2.72), compared to women with central placenta. Mean birth weight and small for gestational age (SGA) rates were similar between groups. Our findings suggest that lateral placenta may be associated with increased risk for preterm birth but not for SGA.

The effect of placental laterality at 20-24 gestational weeks on uterine artery doppler indices, fetal growth and preeclampsia

BACKGROUND

This study aimed (i) to assess the potential effect of placental location on uterine artery (UtA) pulsatility index (PI) and offspring birthweight (BW), and (ii) to examine the potential association of unilaterally increased UtA PI with preeclampsia (PE) or low BW.

MATERIALS AND METHODS

This was an asynchronous cohort study of singleton pregnancies between 20⁺⁰ and 23⁺⁶ gestational weeks resulting in live birth, for whom the placental site (posterior, anterior, fundal, previa, right lateral, or left lateral) and bilateral UtA PI measurements were recorded. The effect of placental location on mean BW and UtA mean PI z-scores was assessed using t-test or ANOVA and post-hoc tests, as appropriate. The UtA PI measurements were then grouped into three categories (normal mean PI; unilaterally increased PI with normal mean; increased mean PI) and we calculated the odds ratios (ORs) of unilaterally increased or increased mean PI vs. normal mean PI for PE, BW <10th centile and BW <5th centile. The independent association of placental location, UtA PI category (normal mean, unilateral increase with normal mean, increased mean PI) and UtA PI z-score with PE, BW <10th centile and BW <5th centile was then assessed using logistic regression.

RESULTS

The analysis included 5506 pregnancies. A lateral placenta was associated with higher mean PI z-score (p = .0001) and lower BW (p = .003) than non-lateral placenta. Compared with normal mean UtA PI, a unilaterally increased PI with a normal mean was associated with increased risk for PE (OR 4.3, 95%CI 1.9-9.7), BW <10th centile (OR 1.7, 95%CI 1.3-2.4) and BW <5th centile (OR 1.8, 95%CI 1.1-2.9). Similarly, increased mean UtA PI was also associated with increased risk for PE, BW <10th and BW <5th centile (OR 9.1, 95%CI 4.8-17.3; OR 4.4, 95%CI 3.5-5.7; OR 7.0, 95%CI 5.1-9.6, respectively). When assessing the independent association of placental location and UtA PI with PE and low BW, only mean UtA PI remains a significant predictor.

CONCLUSIONS

A lateral placenta is associated with a higher mean UtA PI and lower BW. Unilaterally increased UtA PI still carries a greater risk of PE and low BW than bilaterally normal PI, however this effect appears to be eventually mediated through mean UtA PI z-score, which is relatively increased in these cases.

[Placental Locations in Subsequent Pregnancies - A Retrospective Study]

INTRODUCTION

Different locations of the placenta are associated with specific risks during pregnancy and labor. Knowledge of the placental location helps to provide better care for the expectant mother and her unborn child. Whereas multiple studies show a higher risk for a recurrent placenta previa, hardly any such data is available for any other placental location. The aim of this study was to analyze the frequency of distribution of different placental locations and to evaluate correlations between placental locations in subsequent pregnancies.

MATERIAL AND METHODS

In a retrospective cohort study women with singleton pregnancies ≥ 24 gestational weeks who had at least one ultrasound with identification of the placental location and gave birth to their firstborn and at least one more following child at our hospital between 2007 and 2016 were evaluated. Exclusion criteria were multiple pregnancies, abortions, intrauterine fetal death, and fetal malformations. Placental locations were classified into anterior, posterior, fundal, right, left, and previa.

RESULTS

Data of 1657 women were analyzed. The most frequent location was anterior, followed by posterior, fundal and lateral, and previa. Statistical analysis showed no significant correlations in subsequent pregnancies regarding placental locations.

CONCLUSION

Placental locations in subsequent pregnancies seem not to be influenced by previous pregnancies. Therefore no prognosis for placental location can be made concerning future pregnancies.

Placental location and pregnancy outcomes in nulliparous women: A population-based cohort study

INTRODUCTION

The impact of placenta previa on pregnancy, delivery and infant outcomes has been extensively studied. However, less is known about the possible association of placental location other than previa with pregnancy outcomes. The aim of this study was to investigate if placental location other than previa is associated with adverse pregnancy, delivery and infant outcomes.

MATERIAL AND METHODS

This is a population-based cohort study, with data from the regional population-based Stockholm-Gotland Obstetric Cohort, Sweden, from 2008 to 2014. The study population included 74 087 nulliparous women with singleton pregnancies resulting in live-born infants, with information about placental location from the second-trimester ultrasound screening. The association between placental location (fundal, lateral, anterior or posterior) and pregnancy outcomes was estimated using logistic regression analysis. Odds ratios (OR) with 95% confidence intervals (95% CI) were calculated, and adjustments were made for maternal age, height, country of birth, smoking in early pregnancy, sex of the infant and in vitro fertilization. Main outcome measures were pregnancy, delivery and infant outcomes.

RESULTS

Compared with posterior placental location, fundal and lateral placental locations were associated with a number of adverse pregnancy outcomes, the most important being: very preterm birth (<32 weeks of gestation) (adjusted OR [aOR] 1.78, 95% CI 1.18-2.63 and aOR 2.12, 95% CI 1.39-2.25, respectively), moderate preterm birth (32-36 weeks of gestation) (aOR 1.23, 95% CI 1.001-1.51 and aOR 1.62, 95% CI 1.32-2.00, respectively), small-for-gestational-age birth (aOR 1.67, 95% CI 1.34-2.07 and aOR 1.77, 95% CI 1.39-2.25, respectively) and manual removal of the placenta in vaginal births (aOR 3.27, 95% CI 2.68-3.99 and aOR 3.27, 95% CI 2.60-4.10, respectively). Additionally, lateral placental location was associated with preeclampsia (aOR 1.30, 95% CI 1.03-1.65) and severe postpartum hemorrhage (aOR 1.42, 95% CI 1.27-1.82).

CONCLUSIONS

Compared with posterior placental location, fundal and lateral placental locations are associated with a number of adverse pregnancy, delivery and infant outcomes.

Diagnosis of Placental Position by Early First-Trimester Ultrasound: A Pilot Study

OBJECTIVE

Conventional wisdom is that placental location cannot be identified before 8 weeks' gestation when the placenta first becomes hyperechogenic on ultrasound. We sought to evaluate whether placental location could be reliably diagnosed between 5 and 6 weeks' gestation.

MATERIALS AND METHODS

This was a retrospective analysis of prospectively acquired data. Early placental location was diagnosed by evaluation of the embryonal and yolk sac position inside the gestational sac on transvaginal ultrasound. Placental position was described as anterior, posterior, fundal, or lateral. Early and mid-pregnancy placental locations were compared and coded as being the same, having migrated to an adjacent surface, or being on an opposite surface.

RESULTS

A total of 111 patients met study criteria, providing 141 placental locations, comprising 85 singleton and reduced pregnancies and 28 dichorionic twin pregnancies. The most common placental location was anterior in both singleton and twin/triplet pregnancies. Placental location at the mid-pregnancy ultrasound was consistent with early pregnancy location in 100% of cases, with 79.5% (112/141) being on the same surface and 20.5% (29/141) having expanded onto an adjacent surface. Placental location was not associated with pregnancy outcome, although our study may have been underpowered to detect a significant difference.

CONCLUSIONS

Placental location diagnosed at 5 to 6 weeks' gestation is consistent with the location on mid-pregnancy ultrasound. Excluding the presence of an ectopic, cornual, or cesarean section scar and uterine subseptation pregnancy in early first trimester would allow a more effective tailoring of pregnancy follow-up.

Placental Location and the Development of Hypertensive Disorders of Pregnancy

OBJECTIVES

Abnormal placentation is an important factor in the pathogenesis of preeclampsia. As a result of diminished blood flow, the incidence of preeclampsia might be higher in patients with laterally located placentas compared to patients with centrally located placentas. The objective of this study was to evaluate the relationship between placental location and the development of hypertensive disorders of pregnancy.

METHODS

Patients with singleton pregnancies who were seen in our ultrasound unit and delivered at our institution from October 2014 to April 2015 were included. The incidence of hypertensive disorders was compared in those with a lateral placental location and those with centrally located placentas (placental locations other than lateral). Baseline characteristics and pregnancy outcomes were compared between groups. The χ² test, Fisher exact test, Mann-Whitney U test, and t test were used when appropriate. P < .05 was considered significant.

RESULTS

We included 464 patients; 411 (88.57%) had centrally located placentas, and 53 (11.42%) had laterally located placentas. The incidence of hypertensive disorders of pregnancy was similar between groups (21% versus 19%; P = .71). Gestational age at delivery (P = .73), and small for gestational age (P = .96) were also similar between our study groups.

CONCLUSIONS

In our study, there was no difference in the rate of hypertensive disorders of pregnancy between patients with central and laterally located placentas.

Nonpresenting Dichorionic Twins and Placental Vascular Malperfusion

OBJECTIVE

To explore the hypothesis that selective placental pathology affecting the nonpresenting twin is a significant contributory factor mediating the smaller size at birth of nonpresenting dichorionic twins.

METHODS

We conducted a retrospective cohort study of all dichorionic twin deliveries in a single tertiary center between 2002 and 2015 where by departmental policy, all placentas from multifetal gestations are routinely sent for pathologic examination. Maternal charts, neonatal charts, and pathology reports were reviewed. Placental abnormalities were classified into lesions associated with maternal vascular malperfusion, fetal vascular malperfusion, placental hemorrhage, and chronic villitis. Comparison of neonatal outcomes and placental abnormalities was made between all nonpresenting and all presenting twins as well as within twin pairs.

RESULTS

A total of 1,322 women with dichorionic twins were studied. Nonpresenting twins were smaller at birth compared with the presenting cotwin starting at 32 weeks of gestation (birth weight [±standard deviation] 2,224±666 g compared with 2,278±675 g, P=.036). Nonpresenting twins had smaller placentas (361±108 g compared with 492±129 g, P<.001) as early as 24 weeks of gestation. Nonpresenting twins had higher odds for any placental abnormality (adjusted odds ratio [OR] 1.91, 95% confidence interval [95% CI] 1.63-2.23), small placenta (adjusted OR 4.69, 95% CI 3.75-5.88), and maternal vascular malperfusion (OR 2.75, 95% CI 2.32-3.27) compared with their presenting cotwins. In nonpresenting twins, the presence of maternal vascular malperfusion pathology was associated with lower birth weight compared with their presenting cotwin during the third trimester.

CONCLUSION

The lower birth weight of nonpresenting fetuses in dichorionic twin pregnancies is correlated with a higher rate of placental maternal vascular malperfusion pathology.

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.

Is lateral localisation of placenta a risk factor for adverse perinatal outcomes?

The aim of this study was to evaluate the relationship between placental localisation and perinatal outcomes. This study was performed in a tertiary centre hospital by retrospectively analysing the medical records of patients who were followed up and underwent delivery in the same hospital. The patients were divided into two groups according to the placental locations (central and lateral) in their routine sonographic findings between the 18 and 24 weeks' gestation. Out of 1,057 patients, 87.4% (n = 919) had centrally located placentas and 12.6% (n = 133) had laterally located placentas. Preeclampsia was found to be significantly higher in the lateral placental location group (4.5% vs. 1.6%; p = 0.027). There was a significant correlation with foetal growth restriction (FGR), preterm birth rates, low Apgar scores and need for neonatal intensive care unit in the lateral placental location group (p < 0.05). The pregnant women with laterally located placentas should be followed up promptly with special care for the risk of preeclampsia and FGR, and poor neonatal outcomes.

Anterior placental location influences onset and progress of labor and postpartum outcome

INTRODUCTION

The aim of the study is to evaluate whether placental location at term is associated with delivery outcome.

METHODS

A prospective study including 2354 patients with singleton pregnancy at term admitted for vaginal delivery was conducted. Placental position was determined before delivery by ultrasonographic examination performed transabdominally with women in the supine position. Maternal characteristics and delivery outcome such as premature rupture of membranes, induction of labor, mode and gestational age at delivery, indication for cesarean section, duration of the third stage, postpartum hemorrhage (PPH) and manual removal of placenta were correlated with anterior, posterior or fundal placental locations.

RESULTS

Among women enrolled: i) 1164 had an anterior placenta, ii) 1087 a posterior placenta, iii) 103 a fundal placenta. Women with anterior placenta showed: i) a higher incidence of induction of labor (p = 0.0001), especially for postdate pregnancies and prolonged prelabor rupture of membranes (p < 0.0001), ii) a higher rate of cesarean section rate for failure to progress in labor (p = 0.02), iii) a prolonged third stage (p = 0.01), iv) a higher incidence of manual removal of placenta (p = 0.003) and a higher rate of PPH in vaginal deliveries (p = 0.02).

DISCUSSION

The present study showed the influence of anterior placental location on the course of labor, with a later onset of labor, a higher rate of induction and cesarean section and postpartum complications. The reason for this influence on labor and delivery complications remains to be elucidated.

Placental location and pregnancy outcome

OBJECTIVE

The purpose of this study was to determine if placental location is associated with adverse pregnancy outcome and to assess whether any association exists between different blood groups and location of the placenta.

MATERIAL AND METHODS

Medical records of women were reviewed retrospectively and placental position as documented in the case notes at routine antenatal (20-38 weeks) ultrasonography was identified. Placental position was categorised as anterior, posterior and fundal. Association of placental location with foeto-maternal outcome and different blood groups was noted.

RESULTS

A total 474 case notes of women were analysed for placental location, feto-maternal outcome and blood groups. Anterior placenta was found to have a relation with a greater risk of pregnancy-induced hypertension, gestational diabetes mellitus and placental abruption (p<0.001), while posterior placenta had a significant association with preterm labour (p<0.001). Regarding foetal outcome, an anterior placenta was significantly associated with intrauterine growth retardation and intrauterine foetal death (p<0.001). The majority (54%) of women with an anterior placenta were O-positive blood group, while 46% of women in the posterior placenta group were A-positive blood group (p<0.001).

CONCLUSION

Anterior placental implantation is associated with an increased risk of pregnancy-induced hypertension, gestational diabetes mellitus, placental abruption, intrauterine growth retardation and intrauterine foetal death. Posterior placenta has a significant association with preterm labour and A-positive blood group. Anterior placenta is common in women with O-positive blood group. Placental location may be an important determinant of pregnancy outcome.

Second-trimester placental location and postpartum hemorrhage

OBJECTIVES

The purpose of this study was to assess whether low placentation in the second trimester is an independent risk factor for postpartum hemorrhage.

METHODS

A retrospective cohort study of women undergoing transvaginal sonography between 18 weeks' and 23 weeks 6 days' gestation was conducted. Patients were subdivided into three groups: low-lying placenta (0.1-2.5 cm), marginal previa (touching but not overlapping the os), and complete previa (covering the os). Low placentation was used as a descriptive for all cases (low-lying placenta, marginal previa, and complete previa) in this study. A group of randomly identified control patients with normal placentation was selected for comparison.

RESULTS

During the period of study, 410 women with low placentation were identified. Compared to controls, patients with second-trimester low placentation had increased rates of postpartum hemorrhage and uterotonic use. These increased risks persisted even among women in whom the low placentation resolved (odds ratio, 2.72; 95% confidence interval, 1.46-5.07; odds ratio, 2.18; 95% confidence interval, 1.24-3.84).

CONCLUSIONS

Women with a second-trimester diagnosis of low placentation are at increased risk of postpartum hemorrhage.

Persistence of placenta previa in twin gestations based on gestational age at sonographic detection

OBJECTIVES

The purpose of this study was to evaluate the gestational age at sonographic detection of placenta previa as a predictor of previa persistence until delivery in twin gestations.

METHODS

A retrospective cohort of twin pregnancies with placenta previa in a single ultrasound unit was analyzed from 2005 to 2010. Pregnancies were ascertained from a database. Diagnoses were confirmed by transvaginal imaging. Previa was categorized as complete if the placenta completely covered the internal os or marginal if the inferior placental edge reached within 2 cm. Gestational ages were grouped into intervals from 15 to 35 weeks. The study outcome was placenta previa at delivery. Only twin pregnancies at 25 weeks' gestation and later were analyzed using nonparametric statistics as appropriate, with P < .05 as significant.

RESULTS

Placenta previa was detected in 120 twin pregnancies in the second trimester: 32 complete and 88 marginal. Of those with placenta previa at 15 to 19, 20 to 23, 24 to 27, 28 to 31, and 32 to 35 weeks, previa persisted until delivery in 8.3%, 19.2%, 50%, 75%, and 92.5%, respectively. Only at 15- to 19- and 20- to 23-week intervals was complete previa more likely to persist than marginal previa (P < .001).

CONCLUSIONS

The likelihood of placenta previa persistence in twins is dependent on the gestational age at sonographic detection. Only at earlier gestations does the type of previa affect its persistence. As gestational age advances, the likelihood of resolution of placenta previa diminishes regardless of the type noted.

Placental site in the second trimester of pregnancy and its association with subsequent obstetric outcome

OBJECTIVE

To determine if placental location in the second trimester of pregnancy is associated with adverse pregnancy outcomes.

METHODS

We performed a retrospective study on 16 236 patients having ultrasound examination at 14 to 23 weeks of gestation between 2000 and 2007. The placental location was classified into one of four groups: 'central', 'fundal', 'lateral' and 'covering Os'. Obstetric outcomes of non-central placenta were compared to those with 'central' placenta.

RESULTS

Women with a 'fundal' placenta were at increased risk of developing pre-eclampsia (PET) (odds ratios (OR) = 2.27; 95% confidence intervals (CI), 1.31-3.93), a preterm delivery before 34 weeks (OR = 2.23; 95% CI, 1.18-4.22), a non-vertex presentation (OR = 3.48; 95% CI, 2.49-4.86), undergoing a manual removal of placenta (MROP) following a vaginal delivery (OR = 7.1; 95% CI, 4.24-11.85) and small for gestational age (SGA) (OR = 1.35; 95% CI, 1.03-1.79). Women with a 'lateral' placenta were at increased risk of developing PET (OR = 2.04; 95% CI, 1.28-3.25), spontaneous preterm delivery before 34 weeks (OR = 2.04; 95% CI, 1.04-3.98), MROP (OR = 6.75; 95% CI, 4.4-10.33) and SGA (OR = 1.82; 95% CI, 1.48-2.23). Five women with a 'cover Os' placenta had an increased risk of postpartum haemorrhage (>1000 mL) (OR = 6.18; 95% CI 2.29-16.65) if they had a vaginal delivery.

CONCLUSION

Non-central placental location in the second trimester is associated with an increase risk of adverse obstetric outcome.

High-end arteriolar resistance limits uterine artery blood flow and restricts fetal growth in preeclampsia and gestational hypertension at high altitude

The reduction in infant birth weight and increased frequency of preeclampsia (PE) in high-altitude residents have been attributed to greater placental hypoxia, smaller uterine artery (UA) diameter, and lower UA blood flow (Q(UA)). This cross-sectional case-control study determined UA, common iliac (CI), and external iliac (EI) arterial blood flow in Andeans residing at 3,600-4,100 m, who were either nonpregnant (NP, n = 23), or experiencing normotensive pregnancies (NORM; n = 155), preeclampsia (PE, n = 20), or gestational hypertension (GH, n = 12). Pregnancy enlarged UA diameter to ~0.62 cm in all groups, but indices of end-arteriolar vascular resistance were higher in PE or GH than in NORM. Q(UA) was lower in early-onset (≤34 wk) PE or GH than in NORM, but was normal in late-onset (>34 wk) illness. Left Q(UA) was consistently greater than right in NORM, but the pattern reversed in PE. Although Q(CI) and Q(EI) were higher in PE and GH than NORM, the fraction of Q(CI) distributed to the UA was reduced 2- to 3-fold. Women with early-onset PE delivered preterm, and 43% had stillborn small for gestational age (SGA) babies. Those with GH and late-onset PE delivered at term but had higher frequencies of SGA babies (GH=50%, PE=46% vs. NORM=15%, both P < 0.01). Birth weight was strongly associated with reduced Q(UA) (R(2) = 0.80, P < 0.01), as were disease severity and adverse fetal outcomes. We concluded that high end-arteriolar resistance, not smaller UA diameter, limited Q(UA) and restricted fetal growth in PE and GH. These are, to our knowledge, the first quantitative measurements of Q(UA) and pelvic blood flow in early- vs. late-onset PE in high-altitude residents.

Intrauterine growth restriction and placental location

OBJECTIVE

The purpose of this study was to determine whether an association exists between intrauterine growth restriction (IUGR) and second-trimester placental location.

METHODS

A case-control study was performed in well-dated singleton pregnancies with (n = 67) and without (n = 205) IUGR (defined as estimated fetal weight <10th percentile for gestational age at the last sonographic examination) to investigate the association between IUGR and placental location. Placental location was determined by sonography at 16 to 20 weeks' gestation. Maternal, perinatal, and delivery characteristics were abstracted from medical records. Group comparisons were made by the Student t test, chi(2) analysis, the Fisher exact test, the Wilcoxon test, and analysis of variance. Multivariable logistic regression analysis was used to determine the relationship between IUGR and placental location.

RESULTS

In both groups, the most common placental locations in the second trimester were anterior and posterior. After adjusting for potential confounders (including race, chronic hypertension, and hypertensive disorders of pregnancy), IUGR pregnancies were nearly 4-fold more likely to have lateral placentation (odds ratio, 3.8; 95% confidence interval, 1.3-11.2) compared with anterior or posterior placentation.

CONCLUSIONS

Pregnancies complicated by IUGR are significantly more likely than non-IUGR pregnancies to have lateral placentation in the second trimester.