Use of Maternal Serum Alpha-Fetoprotein Measurment in the Diagnosis of Placental Accretion Compared with 2D and 3D Ultrasound

DISCUSSION

In this study the mean age of placenta previa patients (study group) was 32.0 ± 3.3 years while that of upper segment implanted placenta (control group) was 30.3 ± 4.0 years. Moreover the number of previous cesarean sections in the study group was 2.9 ± 1.0 CS, while the control group was 2.5 ± 0.6 CS. While the mean number of parity for the study group was 3.3 ± 1.0 and that of the control group 2.8 ± 0.9.

Also, the mean age of the adherent placenta previa was 31.9 ± 3.7 while the mean age of non-adherent placenta previa was 32.0 ± 3.1. Which showed no significance between the two groups. Also the parity between two groups showed no significance. However the mean number of CS in the adherent placenta previa was 3.2 ± 1.0 while the mean number of previous CS in the non-adherent placenta previa was 2.5 ± 0.7 which shows significant between both groups, which proves that previous CS is a risk factor for adherent placenta.

Assessment of placenta intra-operatively among the group with placenta previa showed 30 (60 %) patients with adherent placentas and 20 (40 %) patients with non-adherent placentas. On the other hand none of the patients of the control group showed adherent placenta, which proves that placenta previa is the main risk factor for adherent placenta.

The final pathological analysis of the 30 patients with adherent placenta revealed 20 cases of placenta accreta, 5 cases of placenta increta and 5 cases of placenta percreta. All of these patients underwent CS hysterectomy. The 5 patients with placenta percreta, the placenta invaded the bladder and had primary bladder repair during the operation.

In 20 of the 50 patients, the conclusive diagnosis of placenta previa without accreta was made. Due to uncontrollable bleeding from the implantation site following placental separation, two of these patients underwent caesarean hysterectomy.

The mean value of MS-AFP of the cases of placenta previa was 139.0 ± 74.4 IU/ml where abnormal elevations (>2.5 MoM) were found in 40 out of the 50 patients with mean gestational age of 36.9 ± 0.8 weeks while the control group showed mean value of 41.9 ± 19.2 ng/ml where only two of the patients showed abnormal elevations, with mean gestational age of 37.2 ± 0.6 weeks with high significance.

On analyzing MS-AFP within the placenta previa patients we found out that the mean value of MS-AFP of cases of adherent placenta previa was 170.4 ± 70.6 IU/ml were abnormal elevations (>2.5 MoM) were found in 27 out of the 30 patients of placenta accreta, with sensitivity of 88.9 %, while the mean value of MS-AFP of cases of non adherent placenta previa was 56.2 ± 39.4 IU/ml were 13 out of the 20 patients showed abnormal elevations (>2.5 MoM) with a low specificity of 33.3 % but with high significance.

So we could conclude that placenta previa is associated with higher levels MS-AFP than patients with upper segment implanted placenta, and patients with placenta accreta are associated with even higher elevations of MS-AFP with high sensitivity but with low specificity.The mean value of MS-AFP according to the type of placenta accreta was 179.3 ± 67.1 IU/ml for placenta accreta, 127.3 ± 82.6 IU/ml for placenta increta and 177.7 ± 86.4 IU/ml for placenta percreta, which showed no significance between the 3 groups.Bahadue et al.¹¹ found a link between higher MS-AFP levels and a higher risk of persisting placenta previa, which is similar to our findings. A MSAFP score of less than 1 MoM is linked to a lower probability of previa persistence until birth.

Furthermore, Zelop et al.¹² discovered elevated MS-AFP levels (between 2.3 and 5.5 MoMs) in 45 percent of 11 women with placenta accreta, whereas none of the controls with placenta previa without accreta did. Although these studies are small, they suggest that women with elevated MSAFP levels with no other obvious cause should be considered at increased risk of placenta accreta.It's also been suggested that in women with placenta accreta, abnormalities in the placental-uterine interface cause foetal alpha-fetoprotein to seep into the maternal blood, resulting in higher MS-AFP levels. ¹²

Similarly, Belfort et al.¹³ found that increased maternal blood alpha-fetoprotein has been linked to placenta accreta, and that there is a clear link between the amount of invasion and the elevation of this analyte. Similarly, Mosbeh et al.¹⁴ discovered that a maternal blood alpha-fetoprotein level of >2.5 MoM is linked to placenta accreta. In addition, Matsuzaki et al.¹⁵ showed that 9 of the 20 (45 percent) women with placenta accreta had increased MS-AFP levels (between 2.7 and 40.3 multiples of the median [MoM]), whereas the controls all had MS-AFP levels within normal limits (less than 2.0 MoM).

Regarding ultrasonographic diagnosis, when we compared greyscale ultrasound to 3D Doppler in the diagnosis of placenta accreta within patients with placenta previa.Intraoperative 30 (60 %) of patients in the study group showed placenta accreta while 20 (40 %) of the patients did not show placenta accrete.With greyscale ultrasound 23 patients (77.8%) showed at least one criterion for placenta accreta, while 7 patients did not show evidence of placenta accrete for the 30 patient confirmed intraoperative as accreta. While with 3D power Doppler 20 patients (66.7%) showed at least one criterion for placenta accreta, while 10 patients did not show evidence of placenta accrete for the 30 patient confirmed intraoperative as accreta.

Comparing the results of the greyscale ultrasound to the definitive diagnosis intraoperative we find that, greyscale ultrasound successfully diagnosed 23 out of the 30 cases of placenta accreta and failed to diagnose the remaining 7 cases with sensitivity of 77.8 %. Also, greyscale ultrasound successfully diagnosed non-adherent placenta in 13 out of the 20 patients and showed criteria of adherence in the 7 remaining patients with specificity of 66.7 %. Positive predictive value 77.8 % and negative predictive value of 66.7 % with high significance (p value 0.02).

Also, on comparing 3D power Doppler results to intraoperative diagnosis, 3D power Doppler successfully diagnosed 20 patients and failed to diagnose 10 patients with sensitivity of 66.7 %. In addition 3D ultrasound ruled out the diagnosis of placenta accreta in 10 patients and had false positives in 3 patients with specificity of 83.3 % and positive predictive value of 85.7 % and negative predictive value of 62.5 % with high significance (p value 0.01).

According to our study, greyscale ultrasound had a higher sensitivity of 77.8 % and negative predictive value of 66.7 %, while 3D ultrasound showed higher specificity of 83.3 % and higher positive predictive value of 85.7 %. Also the addition of 2D ultrasound to 3D power Doppler will have higher sensitivity of 83.3 % and lower specificity of 66.7 %.

Compared to our study, Fukushima et al.¹⁶ The presence of myometrial thickness less than 1 mm or huge placental lakes has been reported as a symptom of accretion of the placenta When both findings are present, they have a substantial positive predictive value (72 percent ). According to Mittal et al.¹⁷, the most relevant prognostic indicators were disruption of the placental-uterine wall interface and the presence of arteries traversing this site. Using a composite grading approach that included six sonographic observations, these researchers found 89 percent sensitivity and 98 percent specificity. The presence of "many coherent vessels in the basal view" has a 97 percent sensitivity, 92 percent specificity, and 76 percent positive predictive value on 3-dimensional power Doppler, according to a recent study. However, the number of people with placenta accreta who participated in these trials was limited, and there is no consensus on which characteristics are most useful in diagnosing placenta accreta. . Also sonographic detection of these criteria remain user dependent which require experience in the field remain the main drawback of ultrasound diagnosis.Finally, when the three groups were compared, MS-AFP was shown to be the most sensitive, with a sensitivity of 88.9%, followed by greyscale ultrasonography with a sensitivity of 77.8% and 3D power Doppler with a sensitivity of 66.7 percent. However, with a specificity of 33.3 percent, MS-AFP was the least specific, followed by greyscale ultrasonography with a specificity of 66.7 percent. , and 3D power Doppler with a specificity of 83.3 percent.

CONCLUSION

MS-AFP could be an excellent placenta accreta screening test, which, when combined with greyscale ultrasound and 3D power Doppler, could be a good predictor of this important source of maternal morbidity and mortality. In our study, we looked at greyscale ultrasound, 3D power Doppler, and MS-AFP, and discovered that MS-AFP was the most sensitive, with a sensitivity of 88.9%, followed by greyscale ultrasound with 77.8% sensitivity and 3D power Doppler with 66.7 percent sensitivity. MS-AFP, on the other hand, was the least specific, with a specificity of 33.3 percent, followed by greyscale ultrasonography (66.7 percent) and 3D power Doppler (83.3 percent).