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OG1.1-3 | Maternal, Perinatal, Stillbirth and Abortion Statistics — SDL Guide (Part 4)
Self-Assessment
The definitions, denominators, and gestational thresholds in this module are the foundation for all subsequent obstetric learning — they reappear in maternal death reviews, perinatal audits, programme evaluations, and clinical examinations throughout your career. Self-assessment at this stage serves an important consolidation function: it forces active retrieval rather than passive re-reading, which is the mechanism by which these precise figures become durable in memory. Research in medical education consistently shows that students who test themselves on numerical thresholds and classification criteria retain them significantly better than those who simply review the material. Use the questions below to check your command of each definition. For each question, attempt an answer from memory first, then review the explanation. If you identify a gap — especially on denominators, multipliers, or gestational thresholds — return to the relevant section before attempting the cluster assessment.
Key thresholds to confirm you know:
• MMR denominator: 100,000 live births
• Maternal death window: within 42 days of termination of pregnancy
• Perinatal period: 28 weeks gestation to 7 days postnatal
• Stillbirth threshold: ≥28 weeks OR ≥1,000 g
• Abortion threshold: <20 weeks OR <500 g
• India MMR 2018–20: 97 per 100,000 live births
• India NMR 2020: ~20 per 1,000 live births
• India PMR 2020: ~26 per 1,000 total births
SELF-CHECK
The Perinatal Mortality Rate uses which denominator?
A. Live births only
B. Total births (live births plus stillbirths)
C. Women aged 15–49 years
D. Total population
Reveal Answer
Answer: B. Total births (live births plus stillbirths)
The PMR denominator is total births (live births + stillbirths) × 1,000, because stillbirths form part of the numerator and can only be captured if the denominator includes them. Using only live births as denominator — as done for NMR and IMR — would exclude stillbirths from the denominator while they are in the numerator, producing an inflated and incorrect rate.
CLINICAL PEARL
Denominator discipline prevents misclassification errors. Three common calculation mistakes encountered in departmental audits: (1) Computing MMR per 1,000 live births instead of per 100,000 — the result looks 100× smaller than the published figure and cannot be compared with national data. (2) Using live births as the PMR denominator — inflates PMR because macerated stillbirths are in the numerator but not the denominator. (3) Classifying a death from a pre-existing cardiac condition that was aggravated by pregnancy as 'accidental' — it is an indirect maternal death and enters the MMR numerator. When in doubt about classification, the operative question is: 'Would this woman have died at this time if she were not pregnant?' If the answer is 'probably not,' the death is either direct or indirect obstetric.