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

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

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 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

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

There are some basic concepts in perinatal epidemiology :

MEASURING PERINATAL MORTALITY PERINATAL I PERINATAL II

RATES FOR THE STUDY OF PERINATAL PROBLEMS Global rates Specific rates Risk rates

Global Rates: e.g.: Early Neonatal Mortality = Perinatal I Mortality = Number of newborns deaths < 7 days Total of newborns for the period 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 mortality fetal + neonatal deaths < 2.500 grs Total of perinatal deaths Fetal mortality due to eclampsia fetal deaths whose mothers have had eclampsia Total of fetal deaths

Atributable Risk in the population Risk Rates Odds Ratio: for case-control studies Risk Ratio: for cohort studies Atributable 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 pregnancy obstetric history actual pregnancy data labour and delivery maternal and neonatal problems maternal 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: for descriptive epidemiologic purposes The analytical level: for the estimation of risk groups.

Basic Statistics We 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.

Analytical statistics We 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:

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 pregnancy Exposed: mothers with BMI under - 1 standard deviation at last prenatal visit (<35 weeks of gestation). Not exposed; mother >= -1 standard deviation

Adverse result: Intrauterine growth retardartion: damage: weight by gestational age < 10th centile Reference outcome: newborn whose weight by gestational age is > = 10th. Centile Acta Med. Auxol, 31(1), 9-13, 1999

The power of data Managment 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.