Table 1.
Description of different surveillance types, examples, advantages and disadvantages.
| Type of surveillance | Example | Approach | Passive/active | Advantages | Disadvantages |
|---|---|---|---|---|---|
| Case reports, Medicines information systems, Pharma- driven Registries | Vigibase (65) OTIS (66) and ENTIS (67) Medicines Information Centre SA (68) Antiretroviral Pregnancy Registry (69) |
Voluntary reporting of adverse events by clinical staff to a central body | Passive | Detection of signal for congenital anomalies or other adverse outcomes, potential to detect miscarriage. | Sample size usually small, denominator uncertain, difficult to quantify extent of risk, reporting bias |
| Hospital-based surveillance | Tsepamo (46) Eswatini (70) Uganda and Malawi Birth Defects Surveillance projects (74) |
Data collection on pregnancy, exposures and outcomes, + - consented photographs of congenital anomalies, routine case record review + - interview of mothers | Active | Large cohort, comparator/control groups, good quality data when coupled with health system strengthening | Missed miscarriage, home delivery, reliant on accuracy of maternal records |
| Case-control studies | National Birth Defects Prevention study (71) | Matched control group without the outcome of interest enrolled with group where infants born with outcome of interest. Exposures and any other potential risk factors captured from each group and compared |
Active/Passive | Detailed data on specific defects Indication of risk for factors associated with outcome, information bias, information on outcomes not included in the case definition may be limited |
Small cohort depending on number of facilities involved, may not be generalisable to different socio-economic, environmental circumstances |
| Prospective cohort studies | Ubomi Buhle (SA) (72) Western Cape Pregnancy Register (73, 74) |
Prospective collection of data from first ANC visit, through pregnancy and outcome | Active | Health system strengthening focus to improve exposure history, outcome ascertainment, embedded in routine care | Time-consuming, additional resources required, may miss miscarriages, data quality dependant on maternal record |
| Healthcare Data Bases | Western Cape Provincial Health Care Data Base (74) | Clinical records including laboratory tests and other specialist investigations collected electronically as part of standard of care | Active | Large, representative cohort, Data linked to pharmacy dispensing records, laboratory results, specialist services, using unique identifier | Date of conception and gestational age usually unknown Challenges in controlling for bias and confounding |