Precise mid-trimester placenta localisation: Does it predict adverse outcomes?

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.

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.

Anterior placenta previa in the mid-trimester of pregnancy as a risk factor for neonatal respiratory distress syndrome

This study investigated whether anterior placenta previa in the second trimester is associated with neonatal respiratory distress syndrome (RDS). The neonates delivered by 2067 women between 2007 and 2015 were evaluated for the presence of RDS through birth records. The location of the placenta and the presence of placenta previa during the second and third trimesters were assessed and recorded. Demographic, prenatal, and perinatal records were reviewed. Anterior placenta previa in the second and third trimesters was correlated with RDS. Infants with lower gestational ages and birth weights had higher rates of RDS. Multivariate logistic regression analysis identified a significant association between anterior placenta previa in the second trimester and neonatal RDS. Anterior placenta previa in the second trimester is associated with neonatal RDS. Obstetricians should be aware that anterior placenta previa detected during the second trimester, irrespective of whether the placenta will migrate in the third trimester, may be an independent risk factor for neonatal RDS.

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.

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.

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.