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ORIGINAL ARTICLE
Year : 2022  |  Volume : 25  |  Issue : 7  |  Page : 1050-1055

Relationship between placenta location and adverse pregnancy outcomes in a nigerian tertiary health facility


1 Department of Radiology, College of Medicine, Faculty of Clinical Sciences University of Ibadan; Institute of Cardiovascular Diseases, College of Medicine University of Ibadan, Ibadan, Nigeria
2 Department of Obstetrics and Gynaecology College of Medicine, Faculty of Clinical Sciences University of Ibadan; Institute of Advance Medical Research and Training, College of Medicine, University of Ibadan, Nigeria
3 Department of Obstetrics and Gynaecology College of Medicine, Faculty of Clinical Sciences University of Ibadan, Nigeria
4 Department of Radiology, College of Medicine, Faculty of Clinical Sciences University of Ibadan, Ibadan, Nigeria

Date of Submission01-May-2021
Date of Acceptance12-May-2022
Date of Web Publication20-Jul-2022

Correspondence Address:
Dr. I O Morhason-Bello
Department of Obstetrics and Gynaecology College of Medicine, Faculty of Clinical Sciences University of Ibadan
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njcp.njcp_1473_21

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   Abstract 


Background: There is evidence that placenta site location might be associated with some adverse maternal and fetal outcomes, however, there is lack of information on this observation in Nigeria and many other developing countries where routine ultrasound is performed as part of antenatal care. Aim: To determine the relationship between placenta location on ultrasonography and adverse pregnancy outcomes among a cohort of women with singleton pregnancies. Materials and Methods: In a longitudinal study among pregnant women from the antenatal clinic of a tertiary health institution in Nigeria. The demographic, clinical parameters, the ultrasonographic placenta location, and pregnancy outcomes of women followed until delivery, or pregnancy termination were documented and analyzed; P > 0.05 was statistically significant. Result: One hundred and fifty singleton pregnant women (43 high risk and 107 normal gestations) were studied. The placenta location was anterior in 72 (48%), posterior in 59 (39.3%), fundal in 10 (6.7%) and lateral in 9 (6.0%) cases. Pregnancies with fundal placenta 8/10 (80%) had more preterm birth compared to 23/72 (31.9%), 11/59 (18.6%) and 2/9 (22.2%) that had anterior, posterior and lateral placenta (P = 0.001) respectively. The mean gestational age (GA) at delivery in those with fundal (34.0 ± 3.9 weeks), anterior (37.0 ± 2.7 weeks), lateral (37.7 ± 1.8 weeks), and posterior placenta (37.7 ± 1.8 weeks) was significantly different P < 0.001. In addition, there was a significant difference in the mean birth weight at delivery in women with fundal (2.09 ± 0.99 kg), anterior (2.84 ± 0.7 kg), posterior (3.0 ± 0.65 kg) and lateral placenta (3.0 ± 0.65 kg) respectively P = 0.002. Conclusion: This study showed that placenta location by ultrasound may be associated with some adverse pregnancy outcomes. The placenta located in the fundus was more likely to be associated with preterm birth and prematurity.

Keywords: Adverse pregnancy outcomes, Nigeria, placenta location, ultrasonography


How to cite this article:
Adekanmi A J, Morhason-Bello I O, Roberts A, Adeyinka A O. Relationship between placenta location and adverse pregnancy outcomes in a nigerian tertiary health facility. Niger J Clin Pract 2022;25:1050-5

How to cite this URL:
Adekanmi A J, Morhason-Bello I O, Roberts A, Adeyinka A O. Relationship between placenta location and adverse pregnancy outcomes in a nigerian tertiary health facility. Niger J Clin Pract [serial online] 2022 [cited 2022 Aug 8];25:1050-5. Available from: https://www.njcponline.com/text.asp?2022/25/7/1050/351446




   Introduction Top


The placenta serves as an important medium between the mother and the fetus for transmitting metabolic, endocrine, and other vital functions. It is also a vital source of information about the intrauterine environment and may provide clues about events culminating in adverse pregnancy outcomes.[1] Studies from the USA, Europe, and Saudi Arabia have shown a correlation between placenta location, blood supply, and pregnancy outcomes,[1],[2],[3],[4] with placenta related disorders documented as one of the major causes of maternal and perinatal morbidity and mortality.[1],[5] In spite of these reports, the mechanism of placental-related disorders has not been fully understood. However, inadequate trophoblastic invasion from abnormal placentation has been implicated in some of these cases.[5],[6],[7]

The technological advancement in medical imaging and the evolution of ultrasound have made ultrasound imaging an essential element of routine antenatal care (ANC)/prenatal medical care for most pregnant women. Ultrasonography has become an integral tool in evaluating the fetus and other components like the placenta, umbilical cord, and amniotic fluid.[8] Abnormalities in the fetus, amniotic fluid volume, uterine and umbilical arteries Doppler velocimetry at sonography could instantly make the sonographer watchful for a possible pregnancy complication or associated adverse outcomes. Generally, the uterine blood supply has been shown to be unequally distributed, implicating the site of implantation and ensuing placenta location as likely important determining factors of placental blood flow and, consequently pregnancy success.[9] Sonographic evaluation of the site of placental implantation, aside from placental previa and accrete, is often limited to ordinary description without any studies on the association to evaluate possible implications on pregnancy and childbirth.[10],[11],[12],[13],[14]

Several studies, particularly from developed countries, had investigated the relationship between placenta implantation site and associated pregnancy outcomes.[10],[13],[15],[16],[17] Findings from these studies varied in terms of the association between placental location and specific obstetric complications.[18],[19] In contrast, there is a paucity of data on placenta location and its effect on pregnancy outcomes in developing countries where such screening might be beneficial due to the lack of other high technology and laboratory tests to screen and detect adverse pregnancy outcomes. This study was conceived to evaluate sonographic placenta location and it's association with pregnancy outcomes in a Nigerian cohort. As well as bridge the knowledge gap in this area.


   Materials and Methods Top


This was a longitudinal study conducted at the antenatal clinic of the Obstetrics and Gynaecology and the ultrasound suites of the Radiology department and the Labour Ward of the Department of Obstetrics, a foremost tertiary health facility in South-West Nigeria. This was a secondary data analysis of a larger study that was conducted in 2016; details of the methods, including the sample size calculation, have been reported in previous publications.[20],[21] However, the minimum sample size was calculated using this validated formula[22];



Where n = minimum sample required; z = standard normal deviation = 1.96 (at 95% confidence level); d = sample error = 5%=0.05; P = prevalence of hypertension in pregnancy of 0.103.[23]

Therefore: n = (1.96) 2 (0.103) (1-0.103)/(0.05) 2

n = 3.84x0.103x0.897/0.0025

n = 0.3549/0.0025

n = 141.97

To account for attrition, the minimum sample size was increased to 150. Consecutive sampling method was used to recruit study participants.

This analysis included 150 healthy singleton pregnant women with a gestational age of 13 weeks to 40 weeks who attended routine antenatal clinic (ANC).

Eligible women were followed up till delivery or fetal demise. All women had an ultrasound examination that described their placental location. Written informed consent was obtained from participants before enrolment into the study. We ensured confidentiality and other ethical principles, including anonymizing personal details for all participants.

Participants were further sub grouped into high-risk pregnancies defined as singleton pregnant women with pre-existing hypertension, diabetes mellitus, kidney disease, heart disease, previous intra-uterine growth restriction, elderly primigravidas, previous PE and hemoglobinopathies. Normal Pregnancies, on the other hand, were singleton pregnancies without any abnormalities or medical condition listed above.

This analysis studied the relationship between ultrasound diagnosis of placental location and pregnancy outcomes. The pregnancy outcomes that were assessed include pregnancy-induced hypertension (PIH), gestational diabetes mellitus (GDM), placental abruption, preterm delivery, intrauterine growth retardation (IUGR), and intrauterine fetal death (IUFD), abortion and neonatal outcome.

Clinical evaluation

The sociodemographic information, and obstetric parameters, including the pregnancy outcomes at the termination of pregnancy or delivery, were documented by the obstetrician in the datasheet.

In this study, adverse pregnancy outcome was defined as preeclampsia, anemia in pregnancy, abruption placenta, or gestational diabetes, stillbirth/abortion, preterm birth, low birth weight, and neonatal intensive care admission.

Ultrasound evaluation

Ultrasonographic examination was performed with a GENERAL ELECTRIC LOGIQ P5 ultrasound scanner (Korea) and a curved array 3.5 -5.0 MHz transabdominal transducer. Two experienced radiologists performed all scans, and the degree of agreement, Kappa, was 95% in a pilot study. The placenta was localized on ultrasound, as a uniformly echogenic (intermediate echogenicity) structure along the uterine wall, with a deep hypoechoic band separating it from the normal uterine myometrium by a radiologist with vast experience in ultrasonography.

After an initial obstetric scan at recruitment to confirm gestational age, to rule out multiple pregnancy and fetal anomalies. Each participant had an obstetric ultrasound for fetal biometry and placental and amniotic fluid evaluation at 24-36 weeks. The details of placental locations of the studied cohort were extracted from the obstetric ultrasound report and were categorized as fundal, anterior, posterior, and lateral in location. The placenta location was recorded for each participant. After the ultrasound, these pregnant women were followed till delivery or termination of pregnancy. Adverse maternal outcomes; PIH, GDM, abruptio placenta, maternal anemia, the gestational age at delivery or termination of pregnancy, birth weight in kilograms, and evidence of fetal distress documented in the datasheet.

Data management

The data collected were analyzed using SPSS 20 spreadsheets. The results obtained were presented using frequency tables, percentages, graphs, means, and standard deviation as necessary. Chi-square or Fisher's exact test was used to test the association between placental location and categorical variables, while the Analysis of variance (ANOVA) was used to test the association between placental location and continuous variables.

A logistic regression analysis was used to test for the relationship between placenta location and preeclampsia, maturity at birth, and small for gestational age, respectively while controlling for maternal age, gravidity, and nature of pregnancy. All test statistics were at a 5% level of statistical significance.


   Result Top


The summary statistics of participants were presented in [Table 1]. The mean age of participants was 31.3 ± 4.22 years with a minimum and maximum years of 22 years and 48 years, respectively. Out of 150 participants, 43 (28.7%) were high-risk pregnancies. The majority of the pregnant women had anterior placental locations while 9 (6.0%) had lateral placenta [Figure 1]. There was no significant difference in age, mean BMI, parity, and nature of pregnancy of the pregnant women by type of placenta location. PIH was observed in 4 (40.0%) of the pregnant women with fundal placenta P = 0.080 [Table 1].
Table 1: Test of association between selected sociodemographic and obstetric parameters and ultrasound diagnosis of placenta location


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Figure 1: Placenta location on ultrasonography in the study population

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Women with fundal placenta had a higher proportion of preterm birth 8 (80.0%) compared to anterior placenta 23 (31.9%), posterior placenta 11 (18.6%), and lateral placenta 2 (22.2%) (P = 0.001). There was a significant difference in the mean GA at delivery among women with various placental locations (P < 0.001). The mean GA at delivery of women with the fundal placenta (34.0 ± 3.9 weeks) was significantly lower than those with the anterior placenta (37.0 ± 2.7 weeks) (P = 0.011), posterior placenta (38.1 ± 2.3 weeks) P < 0.001 and lateral placenta (37.7 ± 1.8 weeks) (P = 0.028), respectively [Table 1]. There was a significant difference in the mean birth weight at delivery among women with various placental locations (P = 0.002). The mean birth weight at delivery of women with fundal placenta (2.09 ± 0.99 kg) was significantly lower than those with anterior placenta (2.84 ± 0.7 kg) (P = 0.016), posterior placenta (3.0 ± 0.65 kg) (p = 0.003) and lateral placenta (3.08 ± 0.41 kg) (P = 0.021), respectively.

The regression analysis showed that the odds of preterm delivery were 13.7 times more likely among pregnant women with fundal placenta location compared to those with anterior placenta location (Adjusted odds ratio (AOR) = 13.7, 95% CI: 2.24-84.20, P = 0.005). [Table 2].
Table 2: Association maternal and perinatal complications with placenta location

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   Discussion Top


There is evidence that placenta abnormalities including coverage or site of placenta implantation, structure, and function of the placenta may be associated with in-utero problems and medical disorders such as preeclampsia.[24],[25] The advent of real-time three/four-dimensional ultrasonography, which allows visualization of in-utero fetal activity during different stages of gestation, has enabled the identification of most severe placental abnormalities before delivery.[18],[26] This is why placenta localization by ultrasound is important, as it may provide some insights into other obstetric problems that may not have physically developed.

In this study, we observed some association between ultrasound diagnosis of placental localization and gestational age at delivery, birth weight, and maturity of the newborn. The placentas located in the fundal region were associated with delivery at the lowest gestational age and lowest birth weight relative to other placental locations. Expectedly, there was a higher proportion of premature babies among pregnant women with placentas located in the uterine fundus.

Similar to a previous study with a relatively small sample population,[9] this study showed no significant association between placental location and maternal characteristics like age, BMI, parity, and gravidity. However, unlike results from a survey by Zia,[9] which reported a significant association between maternal bad obstetrics history and placental location, the pregnancy status of women (high risk or normal pregnancies) in this present study was not significantly associated with the placental site.

Although four (40%) of pregnant women with fundal placental location had a hypertensive disorder, there was no significant relationship between hypertensive disorder among pregnant women and placental location in this study. In contrast, Zia reported a substantial relationship between placental location and PIH.[9] They showed a significant association between the fundal placenta and PIH.[9] However, findings from a population-based cohort study with more than 70,000 nulliparous women with singleton pregnancies resulting in live-born infants, reported that compared to the posterior placental, only lateral placental location was associated with increased risk of preeclampsia.[19] While the small sample size in this present study may be responsible for the non-significant relationship between placental location and PIH, no significant association has been reported between lateral placental site and PIH in previous studies[9] to our knowledge.

Previous studies have suggested that placental location may affect the neonatal outcome.[4] In this study, the mean gestational age at delivery of 34.0 ± 3.9 weeks among women with fundal placenta was significantly lower than in other placenta location sites. Compared with the anterior placenta location, the fundal placental location was associated with an increased risk of preterm delivery. Similarly, a study among 133 patients with a history of preterm premature rupture of the membranes, race, age, parity, and gestational age matched with undelivered pregnant women reported that fundal placental location carries a significantly higher risk of premature rupture of the membrane.[27] The authors explained that the placenta located at the fundus might be associated with the weakest point of the membrane over the cervical os, and this might predispose such women to preterm premature rupture of the membrane.[27] Furthermore, another study reported that very preterm birth (<32 weeks of gestation) and moderate preterm birth (32 to 36 weeks of pregnancy) were more common in women with fundal or lateral placental locations compared to those with a posterior placental site.[19] The authors suggested that the relatively sharp-angled part of the uterus at the fundus, as well as the distance of the fundus to the main communicating vessels of the uterine blood, can potentially compromise placenta function and a resultant adverse pregnancy outcome.[19] Similar to this study, we observed that placental location is not directly associated with PIH.[19]

Contrary to results from previous studies, the placental location was not significantly associated with fetal distress or SGA in this study.[19],[28] Although this study was conducted with relatively small sample size, the proportion of the various placental locations in our study was comparable to the ratios observed in some of the largest studies on the relationship between placental site and pregnancy outcomes.[19],[29]

The interpretation of this study is limited for some reasons. This was a secondary data analysis of a large dataset that was not primarily designed for this study. Although there was a significant difference in the distribution of gravidity between the population in the extracted data and that of the larger data set, distributions of other characteristics like maternal age, parity, and gestational age at delivery was not significantly different between the two data sets. Secondly, this analysis did not account for other possible confounders that could determine the gestational age of delivery, preterm birth, and prematurity. Despite these limitations, this study provided clinical information that may be useful in low-resource settings where other high-technology screening methods for adverse pregnancy outcomes may be scarce. Our findings provided some evidence that placental localization has other benefits aside from using it to determine the mode of delivery, especially when it is low lying.

In conclusion, this study shows that ultrasound diagnosis of placenta location during the antenatal period may provide some useful hints on the possibility of an adverse pregnancy outcome. We observed that the placenta located in the fundus has the highest possibility of being associated with preterm delivery, low birth weight, and premature babies. We recommend a large longitudinal study that will allow causality to be established between potential explanatory variables and the location of the placenta.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patients have given their consent for their clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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