European Journal of Cardiovascular Medicine

Placenta Accreta Spectrum (PAS) encompasses a range of life-threatening obstetric conditions where the placenta adheres abnormally to the uterine myometrium. This spectrum includes placenta accreta (chorionic villi attach to the myometrium without intervening decidua), placenta increta (villi invade into the myometrium), and placenta percreta (villi penetrate through the myometrium, potentially invading adjacent organs). The International Federation of Gynecology and Obstetrics (FIGO) has provided consensus guidelines and a clinical classification system for these disorders to standardize diagnosis and management. PAS is a major contributor to severe maternal morbidity, including massive obstetric hemorrhage, the need for blood transfusions, peripartum hysterectomy, intensive care unit (ICU) admission, and injury to pelvic organs, and can, in severe cases, lead to maternal mortality.

A concerning trend is the rising incidence of PAS globally, an increase largely paralleling the escalating rates of cesarean deliveries. Uterine scarring from previous surgeries, particularly cesarean sections, is a primary predisposing factor. Such scars can lead to defective decidualization at the implantation site, specifically an absent or deficient Nitabuch's layer, which normally forms a barrier to prevent excessive trophoblastic invasion.

A low-lying placenta (LLP), defined as a placental edge located within 20 mm of the internal cervical os on ultrasound examination, or placenta previa, where the placenta partially or completely covers the internal os , are significant risk factors for PAS. This risk is substantially amplified when LLP or placenta previa coexists with a history of prior cesarean sections, as the placenta is more likely to implant over the scarred, vulnerable lower uterine segment. This convergence of a compromised uterine environment (scar) and placental proximity to this area (LLP/previa) creates a high-risk scenario for the development of PAS. Other risk factors for abnormal placental location and PAS include advanced maternal age, multiparity, a history of uterine curettage, smoking, and the use of assisted reproductive technologies (ART).

Maternal serum alpha-fetoprotein (MS-AFP) is a glycoprotein primarily synthesized by the fetal yolk sac, liver, and gastrointestinal tract. It has long been an established biomarker in prenatal screening, historically utilized for the detection of fetal neural tube defects (NTDs) and certain chromosomal aneuploidies during the second trimester. Emerging evidence, however, suggests that unexplained elevations in MS-AFP may also be associated with various adverse pregnancy outcomes linked to placental dysfunction or damage. Several studies have reported an association between elevated MS-AFP levels and an increased risk of placenta accreta. Notably, Kupferminc et al. were among the first to demonstrate a significant link between elevated (1)  MS-AFP and pathologically adherent placenta(1). Subsequent research has further supported this association, particularly in women with placenta previa or LLP.(2,3,4)

The pathophysiological basis for elevated MS-AFP in PAS is thought to be a disruption of the normal maternal-fetal interface. In PAS, the absence or deficiency of the decidua basalis and the Nitabuch's layer allows chorionic villi to invade the myometrium directly. This pathological invasion can compromise the integrity of the placental barrier, leading to increased leakage of AFP from the feto-placental unit into the maternal circulation. Berkeley et al. proposed that such a breakdown in the feto-maternal-placental barrier is responsible for the elevated MS-AFP levels observed. Placental vascular damage or microscopic areas of placental necrosis associated with abnormal implantation might also contribute to this leakage. The level of MS-AFP elevation could, therefore, reflect the extent of this barrier disruption or abnormal trophoblastic activity.

Currently, prenatal diagnosis of PAS primarily relies on ultrasound imaging, often supplemented by magnetic resonance imaging (MRI) in complex cases. While effective, these imaging modalities can be operator-dependent, and their interpretation may be challenging, particularly for posterior placentas or in less experienced hands. Furthermore, access to high-quality imaging and expert interpretation may be limited in some settings. An accessible, non-invasive biomarker like MS-AFP, which is already part of routine antenatal screening in many regions, could offer a valuable adjunctive tool for risk stratification in women with LLP. Identifying women at higher risk for PAS earlier in pregnancy could facilitate timely referral to specialized centers, multidisciplinary team planning, and ultimately, improved maternal and neonatal outcomes.

The rationale for this study is to further elucidate the relationship between MS-AFP and PAS specifically within the context of LLP, a recognized high-risk group. It is hypothesized that elevated second-trimester MS-AFP levels are positively correlated with the presence of PAS in pregnant women with LLP. The primary objectives of this study were to determine the correlation between MS-AFP levels and the presence of PAS in this population and to evaluate the diagnostic utility of MS-AFP as a predictive marker for PAS.

Study Design Observational prospective study

Study Setting and Period The study was conducted at Lalla Ded hospital, a tertiary care centre, located in Srinagar, J&K. Data were collected from August 2023 to January 2023.

Study Population Participants were pregnant women attending the antenatal clinic at the study institution.

Inclusion Criteria:

·        Pregnant women >=18 years age

·        A singleton gestation, with viable fetus, diagnosed with a low-lying placenta (LLP) on a routine mid-trimester ultrasound scan (typically performed >=28 weeks’ gestation), who had undergone maternal serum alpha-fetoprotein (MS-AFP) screening as part of their antenatal care

·        Who delivered at the study institution.

Exclusion Criteria:

·        Women with multiple gestations.

·        Pregnant women with other causes of bleeding during the first, second, or third trimester, including abortion, placental abruption, ectopic pregnancy, polyps, foreign bodies, or local causes of vaginal bleeding.

·        Intrauterine fetal death.

·        History of prior cervical or uterine surgery, except for lower-segment cesarean section and curettage.

·        Presence of any known systemic disease, such as diabetes mellitus, hypertension or hepatic disease.

·        Ovarian tumors.

·        Pregnancy conceived through Assisted Reproductive Technology (ART).

·        Fetal abnormalities, including chromosomal anomalies, congenital malformations such as neural tube defects (spina bifida, anencephaly), gross structural abnormalities, abdominal wall defects (omphalocele, gastroschisis), and skeletal abnormalities.

·        Patients unwilling to participate in the study.

Sample Size and Sampling: A total of 250 participants meeting the inclusion criteria were enrolled in the study. Participants were identified and recruited from the antenatal clinic and hospital admission records during the study period..

Data Collection Procedures: Data were collected from maternal medical records, delivery records, laboratory databases, and histopathology reports using a standardized data extraction form.

●            Maternal Serum Alpha-Fetoprotein (MS-AFP) Measurement: Maternal venous blood samples for MS-AFP screening were drawn >=28 weeks’ gestation, as per routine institutional protocol. MS-AFP levels were determined after taking blood samples and sending to hospital lab. Results were expressed in Multiples of the Median (MoM) for the gestational age. An MS-AFP level 2.5 MoM was defined as "elevated" for the purpose of this study.

●            Diagnosis of Low-Lying Placenta (LLP): LLP was diagnosed when the inferior placental edge was identified by transvaginal ultrasonography (TVS) to be <20 mm from the internal cervical os. The diagnosis was typically made during the routine second-trimester anomaly scan (around [e.g., 18-22] weeks) and confirmed or re-evaluated on a follow-up scan at approximately [e.g., 32] weeks’ gestation, or earlier if clinically indicated.

●            Diagnosis and Confirmation of Placenta Accreta Spectrum (PAS): Prenatal suspicion of PAS was based on standardized sonographic criteria, including the presence of multiple placental lacunae, loss of the normal retroplacental clear (hypoechoic) zone, thinning or interruption of the uterine serosa-bladder interface, and abnormal color Doppler patterns showing turbulent blood flow within lacunae or crossing the myometrium. Magnetic Resonance Imaging (MRI) was utilized in selected cases for further evaluation if ultrasound findings were equivocal or if posterior placentation limited sonographic assessment. The definitive diagnosis of PAS was established based on a combination of intraoperative findings and histopathological examination. Intraoperative criteria included difficulty in manual placental separation, abnormally adherent placental tissue requiring piecemeal removal, and/or excessive, intractable bleeding from the placental bed upon attempted separation. Histopathological confirmation, considered the gold standard, involved microscopic examination of hysterectomy specimens or placental bed biopsies (if performed), demonstrating chorionic villi directly adherent to or invading myometrial fibers, with an absence of the intervening decidua basalis (Nitabuch's layer). Collection of Other Relevant Data: Additional data collected included maternal age, parity, history of previous cesarean sections (number and type), previous uterine surgeries (e.g., myomectomy, dilation and curettage), history of placenta previa or PAS, use of assisted reproductive technology (ART), gestational age at delivery, and details of any maternal complications.

Outcome Measures

The presence or absence of PAS, confirmed by intraoperative and/or histopathological findings.

Statistical Analysis

Descriptive statistics were used to summarize baseline characteristics: means and standard deviations (SD) for normally distributed continuous variables, medians and interquartile ranges (IQR) for non-normally distributed continuous variables, and frequencies and percentages for categorical variables. Comparisons between groups (LLP with PAS vs. LLP without PAS) were made using Student’s t-test or Mann-Whitney U test for continuous variables, as appropriate, and Chi-square test or Fisher’s exact test for categorical variables. The correlation between MS-AFP levels (as MoM) and the presence of PAS was assessed using the diagnostic performance of elevated MS-AFP (using the predefined cutoff) for detecting PAS in women with LLP was evaluated by calculating sensitivity, specificity and overall accuracy, with their respective 95% confidence intervals. A P-value <0.05 was considered statistically significant for all analyses.

Ethical Considerations the study protocol was approved by the Institutional Review Board (IRB)/Ethics Committee of government medical college, Srinagar (Reference Number: IRBGMC/GYNAE 417.Written informed consent was obtained from all participants prior to their inclusion in the study.

A total of 250 pregnant women with a diagnosis of LLP and available MS-AFP results were included in the final analysis.

Table 1: Distribution of study participants based on Maternal Serum Alpha fetoprotein levels.

Table 2: Distribution of study participants based on presence of Placenta Accreta.

Table 3: Association between Maternal Serum Alpha Fetoprotein levels and presence of Placenta Accreta.

                                            *Pearsons chi square test

Table 4: Sensitivity and Specificity of Maternal Serum Alpha Fetoprotein test in predicting Placenta Accreta.

Placenta accreta is a significant contributor to the rising rates of maternal morbidity and mortality, posing serious health risks for both mothers and newborns. This condition can lead to life-threatening complications such as severe postpartum hemorrhage, disseminated intravascular coagulation (DIC), the necessity for hysterectomy, massive blood transfusions, and injuries to the ureter, bladder, and bowel. In extreme cases, it can even result in maternal death. Additionally, neonates born to mothers with placenta accreta spectrum (PAS) disorders are at an increased risk of experiencing adverse perinatal outcomes, including admission to the neonatal intensive care unit (NICU) and respiratory issues such as transient tachypnea of the newborn (TTN).Given the significant maternal and neonatal risks associated with PAS, early and accurate diagnosis has become increasingly crucial. Antenatal detection allows for the timely referral of affected pregnant women to specialized maternity centers equipped to manage high-risk obstetric cases. This proactive approach enables obstetricians to assemble a well-coordinated multidisciplinary care team, ensuring comprehensive perinatal management. It also facilitates meticulous preoperative planning, including the arrangement of advanced surgical techniques, sufficient blood supply, and the optimal scheduling of delivery to minimize complications. With advancements in prenatal screening methods, there is growing interest in exploring the potential correlation between elevated levels of maternal serum alpha-fetoprotein (AFP) and the development of placenta accreta. Emerging research suggests that abnormally high AFP levels detected during pregnancy could serve as an early biomarker for PAS disorders. Identifying these elevated levels in a timely manner would enable healthcare providers to implement appropriate interventions, enhance surveillance strategies, and improve maternal-fetal outcomes. Against this backdrop, the present study aims to investigate the predictive role of maternal serum alpha-fetoprotein as a biomarker for placenta accreta in pregnant women with a low-lying placenta. By enhancing early detection capabilities, this research seeks to contribute to improved clinical management and better prognostic outcomes for both mothers and their newborns.

A total of 250 participants were included in this study, aiming to evaluate the predictive value of maternal serum Alpha-Fetoprotein (AFP) levels (Multiples of Median - MoM) in diagnosing placenta accreta. The findings suggest that AFP serves as a highly reliable biomarker for predicting placenta accreta, with a threshold value of ≥2.5 MoM demonstrating a sensitivity of 86.8% and a specificity of 72.1%. A sensitivity of 86.8% indicates that the Alpha Fetoprotein levels test successfully detects placenta accreta in 86.8% of affected individuals, making it a valuable tool for early diagnosis and a specificity of 72.1% means that the test correctly identifies 72.1% of patients who do not have placenta accrete (Table 4). Among the patients diagnosed with placenta accreta, 33 exhibited raised AFP levels, while only 5 had normal AFP levels. Conversely, in the absence of placenta accreta, 59 patients had raised AFP levels, whereas 153 had normal AFP levels (Table 3). These results indicate that elevated AFP levels can serve as an effective early warning marker for placenta accreta, aiding in timely diagnosis and risk assessment. Our findings align with previous studies that have investigated the role of AFP in placenta accreta prediction. A study conducted by Purashree Sarma et al. in Assam reported a similar sensitivity of 85.17 %(5). Abd El Salam et al. further supported these findings, demonstrating a sensitivity of 88.9% but a lower specificity of 33.3%(6) . Additionally, Jiayi Zhou et al. developed a screening model combining serum biomarkers, including AFP, and reported a sensitivity of 87% for placenta accreta detection. Similarly, Panpan Ma et al. found that AFP (MoM) exhibited a sensitivity of 80% and a specificity of 48.9% in predicting placenta accreta (7) .A retrospective case-control study also analysed Maternal Serum AFP levels in relation to placenta accreta and found a sensitivity of 63% and specificity of 64%(8). These cumulative findings reinforce the diagnostic significance of elevated maternal serum AFP levels in the early identification of placenta accreta. Although AFP alone demonstrates strong predictive value, combining it with other screening modalities may further enhance diagnostic accuracy and clinical decision-making. The integration of AFP screening into routine prenatal care could significantly improve maternal and fetal outcomes by enabling early risk stratification and facilitating timely intervention strategies.

Table 1. presents the distribution of study participants based on Maternal Serum Alpha-Fetoprotein (MSAFP) levels. Our findings indicate that approximately 63% of participants had normal MSAFP levels (<2.5 MoM), while 37% exhibited elevated levels (≥2.5 MoM). Additionally, 15% of participants were diagnosed with placenta accreta, whereas 85% did not have the condition.The prevalence of placenta accreta in our study (15%) closely aligns with findings from previous research. Pooja Verma et al. reported a prevalence of 16%, while Purashree Sarma et al. found it to be 11.8 %(5,9) .These similarities reinforce the reliability of our findings within the context of existing literature. Table 3. illustrates the association between MSAFP levels and the presence of placenta accreta. Among participants with normal MSAFP levels, 5 had placenta accreta, whereas 153 did not. In contrast, among those with elevated MSAFP levels, 33 had placenta accreta, and 59 did not. This clear disparity suggests a significant association between elevated MSAFP levels and placenta accreta.

Our findings are further corroborated by multiple studies. Kupferminc et al. (1) and K.L. Koster et al. reported a significant correlation between increasing MSAFP values and a heightened likelihood of placenta accrete (10). D.J. Lyell et al. also supported these results(11). Additionally, McDuffie R.S. et al. presented a case report linking placenta percreta to high MSAFP levels in the second trimester (13). Hung T.H. et al. identified abnormally elevated AFP as a key risk factor for placenta accrete(14). Similarly, Purashree Sarma et al. reinforced our conclusions (5). Furthermore, a study by Emad Ahmed Fyala demonstrated that MSAFP levels increase with the degree of placental invasion, spanning placenta accreta, increta, and percreta (12). This finding underscores the potential role of MSAFP as a predictive marker for the severity of abnormal placental attachment. Hence MSAFP may serve as a valuable biomarker for early identification and risk stratification of placenta accreta in clinical practice.

This study demonstrates a significant positive correlation between elevated second-trimester maternal serum alpha-fetoprotein levels and the presence of placenta accreta spectrum in pregnant women with a low-lying placenta. The findings suggest that MS-AFP, an established and widely available biomarker, holds potential as a non-invasive adjunctive tool for prenatal risk stratification of PAS in this specific high-risk obstetric population. While not diagnostic in isolation, an elevated MS-AFP in the context of a low-lying placenta should heighten clinical suspicion for PAS, prompting more intensive surveillance and facilitating timely referral for specialized multidisciplinary management, thereby potentially improving maternal and neonatal outcomes. Further large-scale prospective studies are warranted to confirm these findings and to optimize the clinical application of MS-AFP in the prediction of placenta accreta spectrum..

CONFLICT OF INTEREST the authors declare that they have no conflict of interest.

1. Kupferminc MJ, Tamura RK, Wigton TR, Feinberg RF, Lfocus R, Vaisrub N. Placenta accreta is associated with elevated maternal serum alpha-fetoprotein. Obstet Gynecol. 1993 Aug;82(2):266-9.
2. Verma P, Singh KN, Ghanghoriya V. To study analyze maternal serum alpha-fetoprotein as a biomarker of placental adherence in low lying placenta. Int J Reprod Contracept Obstet Gynecol. 2016 Jun;5(6):1959-1963.
3. Sarma P, Das P, Bedre N, Das TS. Maternal serum alpha- fetoprotein as a biomarker of placental adherence in placenta previa. Int J Creat Res Thoughts. 2021;9(1):4670-4676.
4. Kaur J, Kaur AP, Kaur S, Sidhu HK. Study and analysis of maternal serum alpha-fetoprotein levels as a biomarker of placental adherence in low lying placenta. Int J Res Med Sci. 2023 May;11(5):1704-1708.
5. Purashree Sarma, Dr.PanchananDas,Dr. Nikhila Bedre, Dr.Tanma S Das. Maternal serum alpha fetoprotein as a biomarker of placental adherence in placenta previa. IJCRT.2021:9(1);4579-84.
6. Ahmed N, Fareed E and Mofeed F et al. Use of Maternal Serum Alpha Fetoprotein Measurment in the Diagnosis of Placental Accretion Compared with 2D and 3D Ultrasound. AIMJ. 2022:3 (11); 71-76.
7. Ma P, Hu T, Chen Y. The Association and diagnostic value between Maternal Serum Placental Markers and Placenta Previa. Eur J Obstet GynecolReprod Biol X. 2024 Oct 11; 24:100346
8. Berezowsky A, PardoJ, BenZionM, Wiznitzer A, Aviram A. Second trimester biochemical markers as possible predictors of pathological placentation: a retrospective case-control study. Fetal Diagn Ther. (2019) 46:187–92.
9. Pooja Verma, Kavita Singh, VineetaGhanghoriya. To study analyze maternal serum alpha-fetoprotein as a biomarker of placental adherence in low lying placenta. International Journal of Reproduction, Contraception, Obstetrics and Gynecology. 2016:5(6);1959-1963.
10. Koster EL, Dashe JS, McIntire DD, Ramus RM. Association of maternal serum alpha-fetoprotein with persistent placenta previa. J Matern Fetal Neonatal Med. 2004 Jul;16(1):3-7.
11. Lyell DJ, Faucett AM, Baer RJ, Blumenfeld YJ, Druzin ML, El-Sayed YY, Shaw GM, Currier RJ, Jelliffe-Pawlowski LL. Maternal serum markers, characteristics and morbidly adherent placenta in women with previa. J Perinatol. 2015 Aug;35(8):570-4.
12. Emad Ahmed Fyala. Value of measurement of maternal serum alpha fetoprotien in diagnosis of pathologically adherent placenta in cases of placenta pravia. The Egyptian Journal of Fertility of Sterility .2018:22(2).
13. McDuffie RS Jr, Harkness L, McVay RM, Haverkamp AD. Midtrimester hemoperitoneum caused by placenta percreta in association with elevated maternal serum alpha-fetoprotein level. Am J Obstet Gynecol. 1994 Aug;171(2):565-6.
14. Hung TH, Shau WY, Hsieh CC, Chiu TH, Hsu JJ, Hsieh TT. Risk factors for placenta accreta. Obstet Gynecol. 1999 Apr;93(4):545-50..
15.