Download Garretto, D., Stevens, E. Validating a Term BMI using Mode of

Body Mass Index and Pregnancy:
Establishing a “Term BMI”
Diana Garretto, MD & Erin Stevens, MD
State University of New York at Stony Brook University Medical Center
Department of Obstetrics, Gynecology, & Reproductive Medicine
To use the 2009 recommendations by
the Institute of Medicine (IOM) on
weight
gain
during
pregnancy to calculate what the
appropriate BMI at term would be.
PrePregnancy
BMI
BMI (kg/m2)
(WHO criteria)
Underweight
Study Design
The IOM recommends a 28-40 lb
weight gain for underweight pregnant
patients, a 25-35 lb gain for normal
weight, 15-25 lb gain for overweight
and a 11-20 gain for obese. In nonpregnant populations, underweight is
a BMI <18.5, normal weight is a BMI
18.5-24.9, overweight is a BMI 2529.9 and obese is a BMI >30. The BMI
at term was calculated based on the
weight gain recommendations for
underweight,
normal
weight,
overweight and obese patients. BMI
is calculated using the formula BMI =
kg/m2. The BMI calculator at the NIH
website was used to perform the
calculations. Heights of 5’0’, 5’5’,
and 5 ’ 10 ’
were used as
representative heights. Individuals at
5’ were assigned the lower limit of
the weight gain and 5’10’ the upper
limit.
Results
Tables
Objective
Normal Weight
Overweight
Obese (includes
all classes)
Pre-Pregnancy BMI
5’ 0”
103 lbs
BMI = 20
5’ 5”
120 lbs
BMI = 20
5’ 10”
140 lbs
BMI = 20
Total Weight
Gain Range
(lbs)
Rates of weight
gain 2nd and 3rd
trimester (mean
range in lbs/wk)
<18.5
28-40
1 (1-1.3)
18.5-24.9
25-35
1 (0.8-1)
25-29.9
15-25
0.6 (0.5-0.7)
>=30
11-20
0.5 (0.4-0.6)
Weight Gain
Term BMI
25 lbs
5’ 0”
128 lbs
BMI = 25
30 lbs
5’ 5”
150 lbs
BMI = 25
34 lbs
5’ 10”
174 lbs
BMI = 25
A patient would be considered
underweight if the BMI at term was
<23.5, normal weight if the BMI at
term was 23.5-29.9, overweight if
the BMI at term was 30-33.5 and
obese if the BMI at term was >33.5.
Conclusions
A standard BMI at term can be
easily calculated and applied to
obstetric practice. Using the “Term
BMI” at the time of delivery may be
an easier way to objectively assess
risks of obesity at term than weight
alone.
Future Research
Validation of the “ term BMI ” in
regards to mode of delivery,
diabetes, estimated blood loss,
preeclampsia via a retrospective
chart review is currently underway.