Table 1.

Issues related to the measurement of four pregnancy and early childhood health outcomes

	Abortion	Congenital anomalies	Stillbirth	Preterm birth
Circumstances affecting identification	Time after conception. Access to prenatal care. Availability of pregnancy test. Cultural and legal barriers.	Very large number of conditions. Availability of diagnostic tools (systematic surface examination, prenatal, autopsy). Delayed clinical manifestation (internal anomalies, neurodevelopmental defects). Unattended home deliveries.	Masking postnatal death into stillbirth. Cultural barriers.	Contraception methods can affect identification of last menstrual period. Access and timing to prenatal care.
Data elements required for confirmation	Gestational age. Product of conception. Pregnancy test/ultrasound.	Vary with condition. Multiple case definitions needed. Availability of reference test.	Gestational age.	Gestational age.
Clinical variations	Late abortions have different aetiology.	External anomalies more likely to be promptly recognised.	Accuracy of definition depends on gestational age accuracy.	Contraception methods can affect identification of last menstrual period.
Applicability in different types of studies	Few clinical trials include first trimester pregnancies. Pregnancy registries require early identification of pregnancy. Demographic health survey sites have potential to capture cases that did not reach the healthcare system.	MedDRA and ICD used for surveillance. More detailed definitions in observational and clinical studies.	Retrospective studies and surveillance depend on availability of ICD codes. More detailed definitions in observational and clinical studies.	Prospective studies allow for accurate measurement. Retrospective studies are complicated by ascertainment of gestational age.
Aspects that require further testing and review	Gestational age assessment method and cut-off methodology. Definition of early and late abortions. Variable terminology (miscarriage, fetal loss).	Access to the infant. All available terminologies need to be evaluated in different settings.	Gestational age cut-off methodology.	Determination of gestational age in low-resource settings.

ICD, International Classification of Diseases; MedDRA, Medical Dictionary for Regulatory Activities.