| Trimester | No. Specimens | Positive for E. coli (%) | χ2 | P-value |
| First | 26 | 2(8%) |
|
|
| Second | 26 | 2(8%) |
|
|
| Third | 26 | 3(12%) | 49.41 | 0.859 |
| Total | 78 | 7(9.3%) |
|
|