Very Low Weight Gain or Weight Loss Not Recommended for Most Obese Pregnant Women-CME

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April 30, 2010 — Very low weight gain or weight loss is not recommended for

most obese pregnant women, according to the results of a cohort study

reported online March 31 in the *American Journal of Clinical Nutrition*.

" Some clinicians have been pushing weight restriction for all classes of

obese women, " lead author M. Bodnar, PhD, MPH, RD, an assistant

professor of epidemiology, obstetrics, and gynecology at the University of

Pittsburgh in Pittsburgh, Pennsylvania, said in a news release. " Our study

indicates that a single standard for optimal weight gain for obese women may

not fit the bill. Instead, we need to consider level of obesity and advise

women accordingly. "

Because of the lack of data to inform weight gain guidelines by obesity

severity, the 2009 Institute of Medicine (IOM) Committee to Reevaluate

Gestational Weight Gain Guidelines recommended that all obese pregnant women

gain 5 to 9 kg at term. The goal of the present study in obese women who

were stratified by severity of obesity was to evaluate associations between

gestational weight gain and small-for-gestational-age (SGA) births,

large-for-gestational-age (LGA) births, spontaneous preterm births, and

medically indicated preterm births.

The study cohort consisted of singleton, live-born infants without

congenital abnormalities born to mothers in obesity class I (prepregnancy

body mass index [bMI], 30 - 34.9 kg/m2; n = 3254), class II (BMI, 35 - 39.9

kg/m2; n = 1451), and class III (BMI, ≥40 kg/m2; n = 845). Adequacy of

gestational weight gain was defined as the ratio of observed weight gain to

gestational weight gain recommended by the IOM.

With increasing severity of obesity, the prevalence of excessive gestational

weight gain decreased, and weight loss increased. Weight loss tended to

predict SGA, medically indicated preterm births, and spontaneous preterm

births, whereas high weight gain was linked to a higher risk for LGA and

medically indicated preterm births. Probabilities of SGA and LGA were 10% or

less, and the risk for medically indicated preterm births and spontaneous

preterm births were minimal with weight gains of 9.1 to 13.5 kg for obesity

class I, 2.2 to 9 kg for obesity class II, 2.2 to less than 5.0 kg for

obesity class III white women, and less than 2.2 kg for obesity class III

black women.

" These data suggest that the range of gestational weight gain to balance

risks of SGA, LGA, sPTB [spontaneous preterm birth], and iPTB [medically

indicated preterm birth] may vary by severity of obesity, " the study authors

write.

Limitations of this study include observational design, incomplete data on

outcomes related to weight gain and on longer-term infant outcomes, lack of

data on the pattern of weight gain, and lack of data on gestational diabetes

or preeclampsia.

" Obese women may face increased complications of pregnancy, " said senior

author Barbara Abrams, DrPH, RD, professor of epidemiology, maternal and

child health and public health nutrition at the University of California,

Berkeley. " Appropriate weight gain may lessen these risks for the baby, so

we strongly encourage all obese women to receive nutrition and lifestyle

counseling throughout their pregnancies. "

*The National Institutes of Health supported this study. The study authors

have disclosed no relevant financial relationships.*

*Am J Clin Nutr*. Published online March 31, 2010.

Abstract<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve & db=PubMed & li\

st_uids=20357043 & dopt=Abstract>

More information on weight gain during pregnancy is available in the 2009

Institute of Medicine

report<http://www.iom.edu/Reports/2009/Weight-Gain-During-Pregnancy-Reexamining-\

the-Guidelines.aspx>

..

Clinical Context

The rate of class I obesity (BMI, 30 - 34.9 kg/m2) and class II obesity

(BMI, 35 - 39.9 kg/m2) has doubled in the past 30 years. Also, the rate of

class III obesity (BMI, ≥ 40 kg/m2) has tripled, and severe obesity now

affects 65% of reproductive-age women. In 2009, the IOM revised its

guidelines for optimal weight gain in obese women to a general

recommendation of 5 to 9 kg at the end of pregnancy for women with a

pregravid BMI of 30 kg/m2 or higher, but the committee lacked sufficient

data to inform guidelines specific to each class of obesity.

This is a retrospective study of deliveries among women from 1 hospital to

examine the association between obesity and weight gain during pregnancy in

obese women with different classes of obesity and the risk for preterm

delivery and SGA and LGA deliveries.

Study Highlights

- Included were women who delivered singleton live-born infants without

congenital abnormalities at 20 to 42 weeks of gestation between 2003 and

2008.

- Excluded were deliveries with implausible weight changes and missing

data.

- The researchers abstracted prepregnancy weight from prenatal records

using self-report at the first prenatal visit and recalled height from the

mothers' worksheets.

- Of 33,271 women eligible for the study, 4.3% were underweight, 57.0%

were normal weight, 22.0% were overweight, and 16.7% were obese.

- Among obese women (n = 5550), 9.8% had class I obesity, 4.4% had class

II obesity, and 2.5% had class III obesity.

- The 18,950 normal-weight women were used as a comparison group.

- The adequacy of pregnancy weight gain was defined according to the 2009

IOM recommendations for pregnancy weight gain, as a ratio of observed weight

gain to expected weight gain multiplied by 100.

- Expected weight gain was defined as 100% of the 2009 IOM

recommendations (eg, for an obese women delivering at 40 weeks' gestation,

the expected weight gain would be 6.4 kg).

- Birth outcomes were primary outcomes.

- They included SGA, LGA, spontaneous preterm birth, and medically

indicated preterm birth.

- Preterm birth was defined as delivery at completed 20 to less than 37

weeks of gestation.

- SGA and LGA were defined as less than 10th percentile and more than

90th percentile, respectively.

- 78% of women had an ultrasound examination at 20 weeks, which was used

for dating.

- Averaging among the 3 obesity groups, 70.2% of mothers were white, and

28.3% were black.

- 75% were between 20 and 34 years old, half were married, and almost

half were receiving Medicaid insurance.

- Overall, less than 20% of women met 100% of the recommended IOM weight

gain range.

- 25% in obesity class I, 22.4% in class II, and 20.8% in class III

gained 141% to less than 211% of the IOM recommended weight gain.

- As obesity became more severe, weight gain declined and weight loss

increased.

- The adjusted risk for SGA declined as weight gain increased among

mothers in class I, but not class II, and very high weight gain was not

protective.

- Among white women, there was a negative correlation between weight gain

adequacy and SGA risk, but this was not seen in black women.

- Other associations were not affected by race or parity.

- In all classes of obesity, the risk for LGA increased with increasing

weight gain.

- High weight gain was also associated with an increased risk for

medically indicated preterm births.

- High weight gain was associated with a lower risk for SGA but a higher

prevalence of LGA.

- At very high weight gains (≥ 352% of IOM recommendations), the risk for

medically indicated preterm births increased for women with class I obesity

and spontaneous preterm births for class II obesity, but not class III

obesity.

- For women in obesity class III, risks for LGA and medically indicated

preterm births were lowest with weight loss and low weight gain.

- In women with obesity class I, weight gain of 9.1 to 13.5 kg was

associated with probabilities of SGA and LGA of 10% or less and a minimal

risk for medically indicated preterm births and spontaneous preterm births.

For women with class II obesity, the weight gain associated with similar

outcomes was 2.2 to 9 kg.

- For women with class III obesity, the equivalent weight gains for best

outcome were 2.2 to less than 5 kg.

- The authors concluded that the effect of weight gain on pregnancy

outcomes was different in women with different classes of obesity.

Clinical Implications

- Obesity in pregnancy is associated with adverse outcomes of SGA, LGA,

and preterm birth depending on weight gain during pregnancy and severity of

obesity.

- Optimal weight gain for the lowest risk for preterm birth differs among

women with class I, class II, or class III obesity.

--

Ortiz, MS, RD

" I plan on living forever - so far so good "

" Cause of obesity, heart disease and cancer: Look at the end of your fork "