Table 4.
Numbers of pregnancy episodes with recorded outcome missing which were consistent with applied criteria for each scenario*
| Scenario | Description | N of pregnancy episodes with evidence of this scenario (% of total episodes with missing outcome) | N of pregnancy episodes with evidence of this scenario only (% of total episodes with missing outcome) | N of pregnancy episodes with evidence of an outcome in linked HES (% of linkage eligible episodes with recorded outcome missing†) | N of episodes during current registration and UTS follow-up (% of total episodes with missing outcome)* |
| Denominator | 932 604 | 932 604 | 424 375† | 932 604 | |
| Problem 1: The women was pregnant at the time of the database record, but the outcome was not captured in CPRD primary care data. | |||||
| Scenario 1a | The pregnancy outcome occurred in hospital or elsewhere and information wasn’t fed back to the practice. | 211 070 (22.6) | 1934 (0.2) | 211 070 (49.7) | 139 084 (14.9) |
| Scenario 1b | The outcome of the pregnancy is recorded in the primary care data but has no event date associated with it. | 1595 (0.2) | 48 (0.0) | 523 (0.1) | 475 (0.1) |
| Scenario 1c | The pregnancy occurred before the patient was registered at the practice or before UTS. | 415 807 (44.6) | 204 176 (21.9) | 60 423 (14.2) | 0 (0.0) |
| Problem 2: The women was pregnant at the time of the database record, but the pregnancy was still ongoing at the end of available follow-up in the database. | |||||
| Scenario 2a | The patient transferred out or died before the putative end of pregnancy. | 177 557 (19.0) | 40 191 (4.3) | 71 012 (16.7) | 117 571 (12.6) |
| Scenario 2b | The last collection date of the practice was before the putative end of pregnancy. | 65 141 (7.0) | 22 039 (2.4) | 24 091 (5.7) | 58 698 (6.3) |
| Problem 3: The patient was not pregnant at the time of the database record. | |||||
| Scenario 3a | Episode is derived from historical pregnancy information recorded in the first few months after the patient joined the practice. | 10 235 (1.1) | 588 (0.1) | 3058 (0.7) | 3875 (0.4) |
| Scenario 3b | Patient asks for advice while planning a pregnancy. | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) |
| Problem 4: The pregnancy record belongs to another pregnancy episode in the Register. | |||||
| Scenario 4a | Delay in recording the outcome of a pregnancy, algorithm calculates the last menstrual period date (LMP) too late and uncovers records at the beginning of pregnancy creating this pregnancy with recorded outcome missing. | 61 662 (6.6) | 9299 (1.0) | 23 099 (5.4) | 35 255 (3.8) |
| Scenario 4b | The LMP is derived from the data and is wrong resulting in early codes being uncovered creating this episode. | 29 057 (3.1) | 4022 (0.4) | 11 304 (2.7) | 17 110 (1.8) |
| Scenario 4c | The LMP has been shifted earlier in time uncovering records at the end of the pregnancy. | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) |
| Scenario 4d | A code recorded relating to the patient’s delivery history is incorrectly identified by the algorithm as a delivery uncovering records at the end. | 349 874 (37.5) | 113 688 (12.2) | 90 274 (21.3) | 219 505 (23.5) |
| Scenario 4e | The outcome of the pregnancy episode has been misclassified as antenatal | 38 848 (4.2) | 8000 (0.9) | 6611 (1.6) | 18 222 (2.0) |
| None | These pregnancy episodes did not meet the criteria for any identified scenarios. | 106 458 (11.4) | – | – | 94 769 (10.2) |
*A version of this table restricted to episodes which occurred during practice UTS follow-up and patient’s current registration is given in the appendices (online supplemental appendix 16).
†Denominator=pregnancy episodes which had at least 1-day overlap with the available HES follow-up period and where the woman was eligible for linkage.
CPRD, Clinical Practice Research Datalink; HES, Hospital Episode Statistics; UTS, up-to-standard.