Perinatal Epidemiology

14.3.06

Definitions
Perinatal period
• From 24th completed weeks' pregnancy until end of 6th day of life.
• Includes stillbirths.
-Child which has issued forth from mother after 24th weeks of pregnancy.
-Did not at any time after being completely expelled from mother breathe or show other signs of life.

Epidemiology
• Study of distribution and determinants of health-related states/events in specific population.
• Application of study to promote, protect and restore health.
• Person, place, time.

Birth, fertility, mortality
• Crude birth rate.
-Total population.
• Fertility rates.
-Women 15-44 years.
§General.
§Age-specific.
§Total (period).
• Mortality rates.
-Live and stillbirths.
§Still birth.
§Perinatal.
-Live births.
§Neonatal (28 days).
•Early/late.
§Post-neonatal.
§Infant.

Sources of data
• Routine data collection (descriptive epidemiology study).
-Birth registration.
-Death/stillbirth registration.
-Birth notification.
• "Special" data collecting.
-Hospital audit.
-Special studies.
§Cross-sectional.
§Cohort.
§Case control.
§RCTs.

Registration and notification processes
Birth registration
• LEGAL DUTY to register birth within 42 days.
• Usually by parent.
-Infant: name, sex, weight of infant (from notification [record linkage]), plurality.
-Mother: name, address, date and place of birth, occupation.
-Father (if joint-registered or married): as with mother.
-If married: date of marriage, number of previous children (live and stillborn).
• International variations.

Birth notifications
• Responsibility of persons delivering infant.
-Within 36 hours of birth.
• Alerts NHS to birth and hence need for services, triggers NHS number.
-Linked to immunisation and screening in childhood.
• Includes birth weight, gestation and foetal anomalies.
-Record linkage with registration (birth weight).

Birth and infant mortality rates
Headline figures (England and Wales, 2001)
• How many births annually?
594, 634 live births.
-304,635 male (51.2%. F:M ratio = 1:1.050)
-356,548 "within marriage" (60%).
• How many stillbirths?
3,159 stillbirths.
-5.3 per 1,000 live and still births.
-1,725 male (F:M ratio = 1:1.203).
-1, 771 "within marriage" (56%).
• How many deaths?
3,240 deaths under 1 year.
-5.4 per 1,000 live births.
1,420 deaths aged 1-14 years.
-15 per 100,000 population of same age.

So what?
• Time, person, place.
• Descriptive epidemiology study.

Implications and consequences
• Declining birth rate.
-17% fall in crude birth rate in 11 years, compared with 13% fall in general fertility rate.
• Increasing maternal rate.
-18 months in 10 years.
• 7% fall in stillbirths.

Teenage pregnancies
• Peak of 9.5 (1996), trough 8.1.