Fetal growth restriction may be underestimated in obese patients

Only 25% of babies who are born small for their gestational age are diagnosed prenatally, and this under-identification may be even higher in obese patients, according to researchers from The Penn State University College of Medicine. Because fetal growth restriction (FGR) is associated with poor perinatal outcomes, these researchers set out to retrospectively compare the accuracy of a customized growth curve with the standard growth curve (Hadlock), to identify FGR in obese and normal-weight patients.

A total of 300 nulliparous women were included in the single-institution, retrospective study (150 obese women with a body mass index [BMI] >30 mg/k², and 150 women of normal weight with a BMI ≤25 mg/k²). These women were aged 18 to 50 years and gave birth between July 2008 and December 2012.

Obese women were twice as likely to have a fetus classified by third-trimester ultrasound as growth-restricted using the customized curve versus the Hadlock’s curve (odds ratio [OR], 2.1; 95% confidence interval [CI], 1.4−3.2; P = .001). There was no difference in classification of growth restriction found in the women of normal weight (OR, 0.9; CI, 0.7−1.2; P = .41).

“Customized growth curves take into account certain maternal factors such as age, parity, BMI, and ethnicity,” said researcher Megha Gupta, MD. “The standard growth curves still used today were developed in the 1960s to 1980s in Colorado with primarily Caucasian women who did not have their BMI recorded. Those curves are outdated for today’s ethnically diverse population. With 30% of the US population obese, we need to move toward individualized medicine for the fetus.”

“Study limitations include our study’s retrospective nature and the fact that we could not exclude pathology, such as hypertension or smoking, which could have affected these results,” said Dr. Gupta. “We plan to follow this study up with a comparison between Lushenko and Fenton curves, which also are standardized curves for neonatal birth weight, and create customized growth charts. The ultimate goal is a prospective study to see if there are altered outcomes for babies that are detected to be growth-restricted, based on the customized growth chart.”

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