Gestational weight gain may not be a modifiable cause of adverse maternal and infant outcomes. Dr. Jennie Louise, Adelaide University

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SSA SOUTH AUSTRALIAN BRANCH – 22 NOVEMBER MEETING

The South Australian Branch of the Statistical Society would like to invite you to the November meeting of the 2017 program.

Venue: Engineering & Maths EMG06 – Maths seminar room 1, North Terrace, Adelaide University. Campus map is available at http://www.adelaide.edu.au/campuses/northtce/.

***Please note that most entrance doors to Adelaide University buildings close at 6pm so make sure you arrive in time for the talk.

Time:

5.30pm – Refreshments in the Lecture Theatre.

6.05pm – General Meeting Talk.

7.30 pm – A dinner will be held after the meeting at Cafe Michael 2, 204 Rundle Street, Adelaide.

Please rsvp for dinner to [email protected] by 20th November.

 

Speaker: Dr. Jennie Louise, School of Public Health, University of Adelaide

Abstract: In 2009, the US Institute of Medicine issued an updated set of guidelines for Gestational Weight Gain (GWG), recommending that women’s weight gain during pregnancy fall within a prescribed range – differing by pre-pregnancy BMI category- in order to reduce the risk of adverse infant and maternal outcomes. In particular, the focus was on limiting the GWG of women in the overweight and obese BMI ranges.  The IOM guidelines have been widely adopted in clinical practice, and have formed the basis for numerous randomised controlled trials of lifestyle interventions aimed at limiting GWG in overweight or obese women. The results of these trials, however, have been disappointing, with little apparent effect on GWG, and no evidence of improvement in maternal or infant outcomes.

We argue that the focus on GWG may have been misplaced, and that more work must be done to uncover the true causal mechanisms underlying observed associations between increased GWG and adverse outcomes.  Three crucial assumptions underlie the IOM recommendations, namely

  1. GWG is modifiable;
  2. The relationship between GWG and maternal/infant outcomes is causal in nature; and
  3. The causal link between GWG and adverse outcomes is modified by pre-pregnancy BMI category.

Using the published results of studies investigating GWG, and data from the LIMIT trial (the largest of these studies), we demonstrate that there is reason to doubt all three assumptions.  In particular, we consider the nature of the relationship between pre-pregnancy BMI and GWG, and show that the relationship is not adequately captured by BMI categories, and that it is not best characterised as one of effect modification.  Rather, if GWG is causal at all, it should be considered a mediator of the relationship between prepregnancy BMI and adverse outcomes.  However, as we show, the relationships involved are complex, and standard causal mediation models will not be valid for most outcomes of interest.   Nevertheless, in order to identify an appropriate target for intervention in the overweight and obese pregnant population, the correct causal mechanisms must be teased out.

Biography: Jennie Louise was once a philosopher (ethical theory /logic), but she has recovered now.  Having retrained in biostatistics, she now works in the DDASS/AHTA, School of Public Health at the University of Adelaide.  Most of her work involves providing statistical support for large clinical trials and longitudinal studies of pregnancy and early childhood.

Gestational weight gain may not be a modifiable cause of adverse maternal and infant outcomes. Dr. Jennie Louise, Adelaide University
When: 22/11/2017
Time: 5:30 pm - 7:00 pm
Cost: Free
Location: Engineering & Maths EMG06 – Maths seminar room 1,
North Terrace, Adelaide University,
Adelaide,
South Australia 5001
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