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Developing a Child Cohort Research Strategy for Europe http://www.chicosproject.eu Is it the healthiest women who drink alcohol during pregnancy? A CHICOS case study on light drinking in relation to birth weight and preterm delivery Katrine Strandberg-Larsen March 2012 Slide 2 Are there beneficial effects of light drinking? Light drinking is < 1 drink/day A J-shaped curve has been observed for: Birth weight / SGA / IUGR Preterm birth Still birth Behavioural problems Cognitive problems Slide 3 A healthy drinker effect B EHAVIOR MODIFICATION BIAS Widespread consensus that alcohol is harmful during pregnancy Women with a troublesome pregnancy experience will avoid drinking alcohol Women with a high a-priori risk of reproductive failure will be over-represented among non- drinkers C ONFOUNDING Light drinkers are more likely than abstainers to be: From high income households Better educated Older Multiparous (Non-smokers) Slide 4 Experience in the DNBC AJE 2004;159:155-161 Slide 5 Experience in the DNBC AJE 2004;159:155-161 Slide 6 Aim To examine whether the observed beneficial effects of light drinking are attributable to behaviour modification bias or confounding Slide 7 How to examine this? Examine light drinking during pregnancy in relation to birth weight and preterm delivery Restrict to women unaware of their reproductive abilities Examine the paternal alcohol consumption in relation to low birth weight and preterm delivery and compare the maternal and partner associations Slide 8 Reasons to do a CHICOS case study? Restriction to pregnancies in which the women have no reproductive experience is a conservative approach and huge samples are needed to get a sufficient number Few of the existing cohorts have data on paternal alcohol consumption Slide 9 Identification of cohorts A list of European birth cohorts were made A preliminary list of European cohorts (WP 1- June 2011) Cohorts listed at: www.chicosproject.eu/cohort/ www.enrieco.org www.birthcohorts.net Slide 10 Criteria of inclusion Enrolment during pregnancy Enrolment to the cohort was ended or ongoing Enrolled at birth or later n=26 No information on time of enrolment n=3 Enrolled at birth or later n=26 No information on time of enrolment n=3 Enrollment not initiated n=2 Slide 11 Mandatory variables Average weekly alcohol consumption Birth weight Gestational age Gravidity Time to pregnancy Slide 12 Was this information available? Cohort inventories www.enrieco.org www.birthcohorts.net Official web page of cohorts Key references Slide 13 No data on mandatory variables No data on alcohol n=2 Not able to identify data on alcohol n=3 No data on alcohol n=2 Not able to identify data on alcohol n=3 Not able to identify data on gravidity n= 8 No data on time to pregnancy n=2 Not able to identify data on time to pregnancy n=5 Not able to identify data on gravidity n= 8 No data on time to pregnancy n=2 Not able to identify data on time to pregnancy n=5 Slide 14 Included cohorts No response n=4 Refused to participate because lack of payment for data n=1 No response n=4 Refused to participate because lack of payment for data n=1 Incompatible data on alcohol n=1 Ask for consumption in a specific week No information on time to pregnancy n=1 Incompatible data on alcohol n=1 Ask for consumption in a specific week No information on time to pregnancy n=1 Slide 15 The included cohorts CohortCountryYear of enrolment Aarhus Birth CohortDenmark1989- DNBCDenmark1996-2002 Generation RNetherlands2002-2006 HHf2Denmark1984-1987 INMASpain1997,1998, 2004-2008 NINFEAItaly2005+ MoBaNorway1999-2008 PLAGIEFrance2002-2005 Slide 16 Covering of Europe Slide 17 Collaborators Cohort Aarhus Birth CohortTine Brink HenriksenMorten S. Jensen DNBCKatrine Strandberg-LarsenAnne-Marie Nybo Andersen Generation RVincent Jaddoe HHf2Bodil Hammer BechEllen Aagaard Nhr INMAMartine Vrijheid MoBaPer MagnusAne Lunde NINFEALorenzo RichardiFranco Merletti PLAGIESylviane CordierFlorence Rouget Slide 18 PRESENTATION OF COLLABORATORS Slide 19 HOW CAN WE HARMONIZE DATA? Lets start the work: Slide 20 Size of cohorts CohortNumber of live born singletons % enrolled before 36 completed weeks Aarhus Birth Cohort 64,246 99.6 DNBC 87,184 100 Generation R 9,355 99.9 HHf2 11,088 44.5 INMA 3,564 100 MoBa 99,887 99.8 NINFEA 2,791 87.2 PLAGIE 3,319 100 Slide 21 Gestational age at enrolment & birth Slide 22 Slide 23 What we know about gestational age? CohortStatus of cleaningEstimation Aarhus Birth Cohort Yes verified in hospital charts Register based DNBC Yes Register based Generation R Yes US HHf2? INMA Yes US or LMP MoBa? NINFEA No (extreems coded as.) US or LMP PLAGIE Yes Clinical assesment at delivery, LMP & US Slide 24 Gestational age at delivery CohortMeanSDRange Aarhus Birth Cohort 39.51.7623-45 DNBC 39.61.8022-45 Generation R 39.41.8424-43 HHf2 39.81.4727-45 INMA 39.11.6423-44 MoBa 39.51.8222-47 NINFEA 39.81.7223-45 PLAGIE 39.41.5525-42 Slide 25 Birth weight CohortMeanSDRange Aarhus Birth Cohort 3541.2553.2520-6050 DNBC 3585.1565.4510-8700 Generation R 3409.1563.3635-5610 HHf2 3469.5505.5700-5750 INMA 3253.9476.6565-4880 MoBa 3601.1558.8500-6300 NINFEA 3291.4544.1560-5400 PLAGIE 3391.8492.9510-5580 Slide 26 Gestational age & birth weight Slide 27 Slide 28 SHOULD WE DO ANYTHING ABOUT IMPLAUSIBLE BW-GA COMBINATIONS? Your opinions on: Slide 29 We have considered Alexander GR. Obstet & Gynecol 1996 Slide 30 Low birth weight Cohort