Perinatal Epidemiology Andres Bolzan Hospital Maternoinfantil, San Clemente, Argentina. Sociedad Latinoamericana de Investigación Pediátrica, San Clemente, Argentina., San Clemente, Argentina.

Andrés Bolzán Anthropologist, founder member of the Argentinian Association of Biological Anthropology responsible for perinatal epidemiologic surveillance. Hospital San Clemente, Buenos Aires, Argentina.Argentinian Association of Biological Anthropology

The aim of perinatology is to offers health care for persons in gestation, pregnancies and their newborns Perinatology considers the process from 28 weeks of gestation to the first 28 days of life as a continuous linePerinatology considers the process from 28 weeks of gestation to the first 28 days of life as a continuous line

The facts:

We may handle all the information about pregnancies and newborns with a few epidemiologic tools performed by the Latinoamerican Centre for Perinatology and Human Development Latinoamerican Centre for Perinatology and Human Development

Tools for perinatal epidemiology surveillance The Basic Perinatal History The Perinatal Information System The Perinatal Card The Basic Perinatal History The Perinatal Information System The Perinatal Card

There are some basic concepts in perinatal epidemiology :

PERINATAL I PERINATAL II MEASURING PERINATAL MORTALITY

RATES FOR THE STUDY OF PERINATAL PROBLEMS Global ratesGlobal rates Specific ratesSpecific rates Risk ratesRisk rates

Global Rates : e.g.: Early Neonatal Mortality =Early Neonatal Mortality = Number of newborns deaths < 7 days Total of newborns for the period Perinatal I Mortality =Perinatal I Mortality = Late fetal + Early Neonatal deaths Total number of deliveries for the period

Specific Rates, e.g.: Contribution of low birth weight to perinatal mortalityContribution of low birth weight to perinatal mortality fetal + neonatal deaths < grs Total of perinatal deaths Fetal mortality due to eclampsiaFetal mortality due to eclampsia fetal deaths whose mothers have had eclampsia Total of fetal deaths

Risk Rates Odds Ratio :Odds Ratio : for case- control studies Risk RatioRisk Ratio : for cohort studies Atributable Risk in the populationAtributable Risk in the population (supercourse lecture )

Basic statistics in Perinatal Epidemiology I. Obtaining the Basic Data

What are the basic data we should take into account ? Identification of the pregnancyIdentification of the pregnancy obstetric historyobstetric history actual pregnancy dataactual pregnancy data labour and deliverylabour and delivery maternal and neonatal problemsmaternal and neonatal problems maternal and neonatal dischargematernal and neonatal discharge

We can use two registration forms: 1) Perinatal Card : for the mother: is like the PBH, and has got all the basic data. Also is the reference system, because the mother keeps it during all the pregnancy and brings it everywhere for perinatal assistance. 2) Perinatal Basic History (PBH): for the health service. The basic data should be registred there.

Basic statistics in Perinatal Epidemiology II. Analyzing the data

There are two levels of analysis : The Basic Perinatal Statistics :The Basic Perinatal Statistics : for descriptive epidemiologic purposes The analytical level:The analytical level: for the estimation of risk groups.

Basic Statistics Basic Statistic Aditional StatisticsWe may use the Basic Statistic (mortality, morbidity etc.) and the Aditional Statistics (evaluation of prenatal care, breastfeeding, maternal hospitalization etc.) programs of the Perinatal Information System. Then, we´ll be able to describe global rates and some specific rates. Perinatal Information System

Analytical statistics Estimation Risk Epiinfo SpssWe may use the Estimation Risk program of the Perinatal Information System and/or importing data to the Epiinfo or to the Spss programs as.dbf file. To measure the risk, the following data may be defined: Epiinfo Spss Perinatal Information SystemEpiinfoSpss

For the risk factor: For the result: adverse outcome For the risk factor: range of exposed (lower and higher limits) range of not exposed (idem) For the result: adverse outcome (lower and higher limits) reference outcome (idem) let´s see an example:

Risk Factor:Body mass index during pregnancyRisk Factor: Body mass index during pregnancy Exposed: mothers with BMI under - 1 standard deviation at last prenatal visit ( = -1 standard deviation

Adverse result: Intrauterine growth retardartion: damage: weight by gestational age = 10th. Centile Acta Med. Auxol, 31(1), 9-13, 1999 Acta Med. Auxol, 31(1), 9-13, 1999 Adverse result: Intrauterine growth retardartion: damage: weight by gestational age = 10th. Centile Acta Med. Auxol, 31(1), 9-13, 1999 Acta Med. Auxol, 31(1), 9-13, 1999

The power of data Managment of the results for your local researchManagment of the results for your local research

Once we ´ve made basic and additional statistics we are able to: Do an epidemiologic report Explore the real causes of morbidity and mortaltity in order to reduce it. Have an epidemiologic baseline to make health programs.

The reliability of the epidemiologic indicators depends on wether the Perinatal Clinical Forms were filled in completely Then, our first step as an epidemiologist is to recomend the fill of the perinatal histories as good as possible.