Placenta praevia: incidence, risk factors and outcome

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Jun 9, 2015 - respective outcomes of pregnancies with placenta praevia. Methods: Data ... Placenta praevia occurs with an incidence of 0.3–0.5% and is.
http://informahealthcare.com/jmf ISSN: 1476-7058 (print), 1476-4954 (electronic) J Matern Fetal Neonatal Med, Early Online: 1–4 ! 2015 Informa UK Ltd. DOI: 10.3109/14767058.2015.1049152

ORIGINAL ARTICLE

Placenta praevia: incidence, risk factors and outcome Martina Kollmann, Jakob Gaulhofer, Uwe Lang, and Philipp Klaritsch

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Department of Obstetrics and Gynecology, Medical University of Graz, Graz, Austria

Abstract

Keywords

Objective: Aim of this study was to evaluate the incidence, potential risk factors and the respective outcomes of pregnancies with placenta praevia. Methods: Data were prospectively collected from women diagnosed with placenta praevia in 10 Austrian hospitals in in the province of Styria between 1993 and 2012. We analyzed the incidence, potential risk factors and the respective outcomes of pregnancies with placenta praevia. Differences between women with major placenta praevia (complete or partial placenta praevia) and minor placenta praevia (marginal placenta praevia or low-lying placenta) were evaluated. Results: 328 patients with placenta praevia were identified. The province wide incidence of placenta praevia was 0.15%. Maternal morbidity was high (ante-partum bleeding [42.3%], postpartum hemorrhage [7.1%], maternal anemia [30%], comorbid adherent placentation [4%], and hysterectomy [5.2%]) and neonatal complications were frequent (preterm birth [54.9%], low birth weight 52500 g [35.6%], Apgar-score after five minutes 57 [5.8%], and fetal mortality [1.5%]. Women with major placenta praevia had a significant higher incidence of preterm delivery, birthweight 52500 g and Apgar-score after five minutes 57. Conclusions: Placenta praevia was associated with adverse maternal (34.15%) and neonatal (60.06%) outcome. The extent of placenta praevia was not related with differences regarding risk factors and maternal outcome.

Incidence, maternal and neonatal outcome, placenta praevia, risk factors

Objective Placenta praevia occurs with an incidence of 0.3–0.5% and is defined by implantation of the placenta in the lower uterine segment, thus partially or totally overlying the internal os [1]. Diagnosis is usually made during the second half of pregnancy by vaginal or trans-abdominal sonography [2,3]. Terminology, however, is still inconsistent and a need for adequate sonographic criteria has been addressed several times [3,4]. The condition is frequently complicated by invasion of placental villi beyond the decidua basalis causing placenta accreta or increta [5]. Due to the abnormal location and invasion of placental tissue, severe maternal bleeding is likely to occur, especially in the third trimester of pregnancy and with the onset of labor [1,5]. Such abnormal placentation has been observed to be associated with previous caesarean deliveries [5–7] or other uterine surgeries, such as myomectomy or curettage, advanced maternal age, multiparity and smoking [5,6,8]. Whilst there has been a global rise in the number of caesarean deliveries, rates vary considerably within and between countries [9]. In Austria the caesarean Address for correspondence: Philipp Klaritsch, Division of Obstetrics and Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Medical University of Graz, Auenbruggerplatz 14, A-8036 Graz, Austria. Tel: +43 316 385 81641. Fax: +43 316 385 13199. E-mail: [email protected]

History Received 1 May 2015 Accepted 5 May 2015 Published online 4 June 2015

section rate has raised in the last decade from 22 to almost 30% [10], thus increasing the likelihood for abnormal placentation. We therefore aimed to evaluate the incidence and outcome of placenta praevia in our institution, a tertiary referral center, as well as in our associated province hospitals. Additionally we intended to analyze the association with previously reported risk factors.

Methods We performed a study on frequency, perinatal complications, and risk factors in a cohort of pregnant women diagnosed with placenta praevia in our institution and nine referring hospitals in our province. The overall study period covers the time span between March 1993 and October 2012. Data were retrospectively retrieved from the local perinatal database and the medical documentation system or patient files. At our institution, a tertiary referral hospital, data were collected in a purpose designed database from 1993–2003. From 2003 onwards a new electronic perinatal database (PIA, ViewPoint, GE Healthcare, Zipf, Austria) was implemented covering all deliveries across the whole province. Therefore, the study population comprises of women from two decades: the initial population of our institution from 1993 to 2003, and the province-wide population from 2003 to 2012. Our institution

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J Matern Fetal Neonatal Med, Early Online: 1–4

acts as a referral center for pregnancies at risk and therefore we were interested in the evolution of this condition at our unit within the last decade. The study was approved by the institutional review board (Nr: 24-213 ex 11/12). All women diagnosed with any type of placenta praevia including low-lying placenta, were identified. Maternal outcome parameters were comorbid abnormal placentation (placenta accreta, increta or percreta), antepartum bleeding, post-partum hemorrhage of more than 2000 mL, anemia (5100 g/L/6.2 mmol), and intra- or postpartum hysterectomy. Neonatal parameters were gestational age at delivery, birth-weight and length, Apgar-scores after five minutes, as well as neonatal mortality. Information on prior uterine surgeries (caesarean section, myomectomy, curettage with or without hysteroscopy), parity, and smoking was collected. The study population was stratified in two groups with ‘‘major placenta praevia’’ (complete or partial placenta praevia) or ‘‘minor placenta praevia’’ (marginal placenta praevia or low-lying placenta) and evaluated with regard to risk factors and perinatal outcome [11]. Statistical analysis Statistical analyses were performed by using descriptive statistics, Chi-Square-Test and Mann–Whitney-Test, when appropriate, applying a significance level of 50.05 (SPSS, V20.0, IBM Analytics Software, Chicago, IL). Results are presented as odds ratios with 95% confidence intervals (95% CI) and p values.

Results Between January 1993 and October 2012 placenta praevia was diagnosed in 328 women. In this time span a total of 218 876 deliveries occurred in the province resulting in an incidence of 0.15%. Overall mean maternal age was 31.6 (17–46) years and 29.3% (n ¼ 96) were older than 35 years at time of delivery. 187 (57%) women were multiparas. The degree of placental pathology was documented in 209 patients. 82 (39%) presented with a low-lying placenta, 36 (17%) with a marginal placenta praevia, 18 (9%) with a partial, and 73 (35%) with a complete placenta praevia. Perinatal outcome was documented in 326 (99.4%) patients, while information of the prenatal course of pregnancy was available in only 260 (79.3%) cases. In 110

(42.3%) patients ante-partum bleeding occurred while 23 (7.1%) had post-partum hemorrhage and 98 (30.1%) were anemic. In 13 (4.0%) a comorbid abnormal placentation was present and in 17 (5.2%) cases hysterectomy was performed. There was no maternal death in the total population. Mean gestational age at delivery was 35.6 (23–41) weeks of gestation and a total of 179 (54.9%) infants were born 537 weeks of gestation. Mean birth-weight was 2692 g (603–4500) and in 116 (35.6%) newborns it was below 2500 g. In 19 (5.8%) children Apgar-score after five minutes was 57. Five (1.5%) infants died; two pre-natally and three post-natally. Mode of delivery was documented in 297 cases and revealed that 271 (91.2%) women had a caesarean section. Women with a ‘‘major placenta praevia’’ were all delivered by caesarean section and had a significant higher incidence of preterm delivery (OR ¼ 6.04, CI 3.27–11.15, p50.01), birth-weight 52500 g (OR ¼ 3.82, CI 2.05–7.11, p50.01) and Apgar-score after five minutes 57 (OR ¼ 6.39, CI 1.35–30.35, p50.01; Table 1). Delivery was performed one week earlier on average if a ‘‘major placenta praevia’’ was present (35.3 versus 36.4 weeks of gestation, p50.01). We found similar results when comparing the mean birth-weight (2619 versus 2783 g, p50.01), birth length (47.5 versus 48.2 cm, p50.01), and head circumference (33.0 versus 33.3 cm, p50.01). Data on prior uterine surgeries and recurrent abortions were available in 167 (50.9%) cases. 82 (49.1%) patients had a history of uterine surgery, including caesarean section, curettage and hysteroscopy. In our population none had prior myomectomy. The major share were previous caesarean sections, posing 22.8% (n ¼ 38) of the population. Thirty-one (18.5%) patients had one prior caesarean delivery, five (3.0%) two, and one (0.6%) four and five, respectively. Thirty-eight (22.8%) women had prior abortions treated with curettage. Placenta localization in previous pregnancies was documented in 158 (48.2%) cases and 17 (10.8%) of them had a preceding placenta praevia. Risk factors and maternal outcome were not related to the classification of placenta praevia (Tables 1 and 2). At our institution, the tertiary referral center of the province, a total of 23 990 women were delivered from March 2003 to October 2012 including 106 (0.44%) cases with placenta praevia. The local annual incidence increased from 0.36% in 2003 to 0.54% in 2012, with the lowest rate in 2004 (0.26%) and the highest one in 2011 (0.74%).

Table 1. Evaluation with regard to maternal and fetal outcome after stratification to ‘‘major placenta praevia’’ (complete or partial placenta praevia) or ‘‘minor placenta praevia’’ (marginal placenta praevia or low-lying placenta). Major placenta praevia Pregnancy data and perinatal outcome Maternal outcome Antenatal bleeding Anemia (requiring treatment) Postnatal bleeding (42 l) Hysterectomy Fetal outcome Preterm delivery Birth weight 52500 g Apgar-score after 5 min 57

Minor placenta praevia

n

%

n

%

p value

Odds ratio

95% CI

29/69 29/90 9/90 5/90

42.0 32.2 10 5.6

39/102 30/118 6/118 4/118

38.2 25.4 5.1 3.4

n.s. n.s. n.s. n.s.

1.17 1.39 2.07 1.68

0.63–2.18 0.76–2.56 0.71–6.06 0.44–6.43

69/91 42/90 9/90

75.8 46.7 10

40/117 22/118 2/117

34.2 18.6 1.7

50.01 50.01 50.01

6.04 3.82 6.39

3.27–11.15 2.05–7.11 1.35–30.35

Placenta praevia: incidence, risk factors and outcome

DOI: 10.3109/14767058.2015.1049152

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Table 2. Evaluation with regard to risk factors after stratification to ‘‘major placenta praevia’’ (complete or partial placenta praevia) or ‘‘minor placenta praevia’’ (marginal placenta praevia or low-lying placenta). Major placenta praevia Pregnancy data and perinatal outcome Risk factors Prior operations involving uterine cavity Maternal age 435 Prior miscarriage with operative management Prior placenta praevia

Minor placenta praevia

n

%

n

%

p value

Odds ratio

95% CI

43/90 25/91 20/90 9/89

47.8 27.5 22.2 10.1

26/54 27/118 11/54 4/53

48.1 22.9 20.3 7.5

n.s. n.s. n.s. n.s.

0.99 1.28 1.12 1.38

0.59–1.94 0.68–2.39 0.49–2.56 0.40–4.72

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Figure 1. The incidence of placenta praevia increased paralleled by an increase in the rate of caesarean deliveries between 2003 and 2012.

This was paralleled by an increase in the rate of caesarean deliveries from 24.2 to 31.9% (Figure 1).

Conclusions We evaluated the incidence and outcome of placenta praevia as well as the association with previously reported risk factors. Our finding, that the extent of placenta praevia did not differ with regard to risk factors and maternal outcome is important as one may underestimate the significance and risk of a ‘‘minor placenta praevia’’ (low-lying placenta and marginal placenta praevia). The incidence of placenta praevia considerably increased in our unit from 0.36% in 2003 to a maximum of 0.74% in 2011, paralleled by a raise of caesarean deliveries from 24.2 to 31.9%. The relatively high incidence in our center in comparison to the one of the entire province (0.15%) is mainly due to the fact that most complicated pregnancies are referred to our institution, which is also equipped with a neonatal intensive care unit. Nearly half (49.1%) of our patients with a placenta praevia had prior uterine surgery. The most frequent surgical history was obviously caesarean section. In general it seems important to avoid uterine operations whenever possible, especially if there is the wish to preserve fertility. In our institution, caesarean deliveries are only performed when medically indicated. However, in other provincial hospitals, especially the private ones, a considerable number of caesarean deliveries may have been performed on maternal request, which obviously contributed to the increased number of this intervention [9,12]. The increased risk of placental

pathologies in subsequent pregnancies should be emphasized during informed consent for caesarean section. Evidence suggests a correlation between the number of previous caesarean sections and the occurrence of a placenta praevia, uterine rupture and hysterectomy [13]. Therefore, vaginal birth after caesarean delivery may be offered and consenting patients be transferred to institutions with adequate experience [13–16]. A recent review is reporting successful vaginal delivery following one and two caesarean sections in 76.5 and 71.7%, while perinatal hysterectomy was required in only 0.19 and 0.55%, respectively [15]. A substantial number of women in our study population previously underwent curettage due to abortions. These patients may benefit from less invasive approaches [1,17], like medical treatment of missed abortions with misoprostol whenever this is in accordance with clinical and personal prerequisites [18]. In our department, delivery between 35 + 0 and 36 + 0 weeks of gestation is pursued if major placenta praevia (placenta praevia partialis and totalis) is present. Nevertheless, still 42.3% of our patients presented with antepartum bleeding. This number appears high, but we know from other studies that this proportion may reach up to 90% [19]; a strategy of elective preterm delivery seems to reduce this risk. Hysterectomy rate in patients with a placenta praevia ranges between 5 and 19% according to previous studies [20–23]. In 5.2% of our patients hysterectomy was necessary, 29.4% of these presented with a comorbid abnormal placentation. Due to our retrospective study design we could not differ between an anterior or posterior localization of the

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placenta praevia. Jang et al. performed a study looking at different localizations and found that anterior position increases the incidence of excessive blood loss, massive transfusion, placental accreta and hysterectomy. Therefore detailed sonographic determination may contribute in prediction of maternal outcome [22]. Maternal death in association with the presence of a placenta praevia is rare in the western word, but is still a substantial issue in developing countries [5,20,21,23–25]. A major neonatal risk factor increasing adverse outcome is preterm birth. Delivery prior to 37 weeks of gestation occurred in 54.9% of our population. This is genuinely related to elective preterm delivery and therefore unavoidable. As the mean gestational age at delivery was 35.64 weeks of gestation these babies are not extremely preterm. However, recent studies demonstrate that even late preterm babies may face substantial health problems in later life [26,27]. Neonates of women with ‘‘major placenta praevia’’ had a significant worse outcome in our study. It is noteworthy, that the extent of placenta praevia was not related with differences regarding risk factors and maternal outcome. In 3.4% of our patients with a ‘‘minor placenta praevia’’ (low-lying placenta and placenta praevia marginalis) hysterectomy was necessary. This is important as we often tend to underestimate the significance and risk of these entities. We believe that reported numbers are of significance for physicians dealing with affected pregnancies and may help in management of this condition. Placenta praevia is associated with adverse maternal and neonatal outcome and detection and, if possible, prevention of risk factors is therefore important.

Declaration of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

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