Perinatal Perinatal EpidemiologyEpidemiology

Andres BolzanAndres Bolzan

Hospital MaternoinfantilHospital Maternoinfantil, San Clemente, Argentina.

Sociedad Latinoamericana de Sociedad Latinoamericana de Investigación Pediátrica 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 The aim of perinatology is to offers health care for persons in offers health care for persons in gestation, pregnancies and their gestation, pregnancies and their

newbornsnewborns

• Perinatology considers the Perinatology considers the process from 28 weeks of process from 28 weeks of gestation to the first 28 days gestation to the first 28 days of life as a continuous lineof life as a continuous line

The facts: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 surveillanceTools 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 There are some basic concepts in perinatal concepts in perinatal

epidemiology :epidemiology :

PER IN AT AL M O R T ALIT Y

interm ediate20-27 weeks

LAT E28 or m ore weeks

FET AL

EAR LYup to 7 days

LAT Efrom 7 to 28 days

N EO N AT AL

PERINATAL I PERINATAL I

PERINATAL II PERINATAL II

MEASURING PERINATAL MORTALITYMEASURING PERINATAL MORTALITY

RATES FOR THE RATES FOR THE STUDY OF STUDY OF

PERINATAL PERINATAL PROBLEMSPROBLEMS

•Global ratesGlobal rates

•Specific ratesSpecific rates

•Risk ratesRisk rates

Global Rates: e.g.:

• Early Neonatal MortalityEarly Neonatal Mortality = =

Number of newborns deaths < 7 days

Total of newborns for the period

• Perinatal I MortalityPerinatal I Mortality = =

Late fetal + Early Neonatal deaths

Total number of deliveries for the period

Specific RatesSpecific Rates, e.g.:, e.g.:

• Contribution of low birth weight to Contribution of low birth weight to perinatal mortality perinatal mortality

fetal + neonatal deaths < 2.500 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 RatesRisk Rates

•Odds RatioOdds Ratio:: for case-control studies

•Risk RatioRisk Ratio: for cohort studies

•Atributable Risk in the Atributable Risk in the populationpopulation

(supercourse lecture )

Basic statistics in Basic statistics in Perinatal Perinatal

EpidemiologyEpidemiologyI. Obtaining the Basic I. Obtaining the Basic

DataData

What are the basic data we What are the basic data we should take into account ?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 We can use two registration forms: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 Basic statistics in Perinatal Perinatal

EpidemiologyEpidemiologyII. Analyzing the data

There are two levels of There are two levels of analysisanalysis : :

• The Basic Perinatal StatisticsThe Basic Perinatal Statistics:: for descriptive epidemiologic purposes

• The analytical level:The analytical level: for the estimation of risk groups.

Basic StatisticsBasic Statistics• We may use the Basic StatisticBasic Statistic

(mortality , morbidity etc.) and the

AditionalAditional Statistics 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 statisticsAnalytical statistics• We may use the Estimation RiskEstimation 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:For the risk factor:range of exposed (lower and

higher limits)range of not exposed (idem)

For the result:For the result:adverse outcomeadverse outcome (lower and

higher limits)reference outcome (idem)

let´s see an example:

• Risk Factor:Risk Factor: Body mass index Body mass index during pregnancyduring 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.

CentileActa Med. Auxol, 31(1), 9-13, 1999

Adverse result: Intrauterine growth retardartion: damage: weight by gestational age < 10th

centile Reference outcome: newborn whose weight by gestational age is > = 10th.

CentileActa Med. Auxol, 31(1), 9-13, 1999

The power of The power of datadata

• Managment of the Managment of the results for your local results for your local researchresearch

Once we ´ve made basic and Once we ´ve made basic and additional statistics we are able additional statistics we are able

to: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 The reliability of the epidemiologic indicators epidemiologic indicators depends on wether the depends on wether the

Perinatal Clinical Forms were Perinatal Clinical Forms were filled in completelyfilled in completely

Then, our first step as an Then, our first step as an epidemiologist is to recomend epidemiologist is to recomend

the fill of the perinatal the fill of the perinatal histories as good as possible.histories as good as possible.