Is There a Link Between The Degree of Maternal Obesity and Congenital Malformations?

Derek Ebot-Akoachere, Mercer University College of Pharmacy


According to the United States Surgeon General, the Centers for Disease Control and Prevention, and the National Institutes of Health, obesity is a health issue of nationwide epidemic proportions, [1] Almost one-third of women of childbearing age are considered obese [2], and obesity is associated with many pregnancy complications including congenital malformations (CMF). [3] The relationship between obesity in pregnancy and CMF has been investigated, but there is little data associating increasing severity of obesity and CMF.

Risk of major congenital malformations in relation to maternal overweight and obesity severity [4]
Design Population based cohort; N= 1,243,957
Objective To estimate the risks of major congenital malformations in the offspring of mothers who are underweight, overweight, or obese in classes I, II or III compared with normal weight mothers in early pregnancy
Study Groups Underweight (n= 29,864); normal weight (n= 756,432); overweight (n= 311,339); obese I (n= 103,085); obese II (n= 31,883); obese III (n= 11,354)
Methods Singleton births in Sweden from 2001 to 2014 were included.

The following were excluded: multiple births, stillbirths, lack of valid personal identification from the mother and infant, infants with chromosomal aberrations, genetic and malformation syndromes with known causes. Weight categories were classified as follows: underweight (BMI <18.5), normal weight (BMI 18.5 to <25), overweight (BMI 25 to <30), obese I (BMI 30 to <35), obese II (BMI 35 to <40), and obese III (BMI ≥40).

Duration 14 years (2001-2014)
Primary Outcome Measure Presence of any major congenital malformations in liveborn infants
Baseline Characteristics
Maternal age, years n
13-24 178,388
25-29 374,411
30-34 433,659
≥35 257,499
Infant sex
Girl 604,463
Boy 639,494
Maternal country of birth
Nordic (Sweden, Norway, Denmark, Finland, and Iceland) 985,200
Non-nordic 258,757
Smoking status
Non-smoker 1,152,475
1-9 cigarettes/day 69,323
≥10 cigarettes/day 22,159
underweight normal weight overweight obese I obese II obese III
Events, n (%) 1,020 (3.4) 25,713 (3.4) 11,050 (3.5) 3,903 (3.8) 1,335 (4.2) 529 (4.7)
Adjusted risk ratio (95% CI) 1.01 (0.95-1.08) 1.00 (reference) 1.05 (1.02-1.07) 1.12 (1.08-1.15) 1.23 (1.17-1.30) 1.37 (1.26-1.49)
Adverse Events Common Adverse Events: N/A
Serious Adverse Events: N/A
Percentage that Discontinued due to Adverse Events: N/A
Study Author Conclusions The risks of major congenital malformations in offspring progressively increase with maternal overweight and severity of obesity.

Organogenesis occurs within the first eight weeks of gestation. Since preventive effects of weight reduction in early pregnancy cannot be expected past this time, efforts should be made to encourage women of reproductive age to adopt a healthy lifestyle and obtain a normal body weight before conception. The study was restricted to live births, which excludes malformations ending in miscarriage or stillbirth. Maternal height used to calculate BMI was self-reported, which may introduce some degree of recall bias. In the midst of a nationwide obesity epidemic, inspiring patients to improve diet and physical activity before conception may decrease the risk of pregnancy complications, benefiting both mother and child.  


[1] Office of the Surgeon General (US); Office of Disease Prevention and Health Promotion (US); Centers for Disease Control and Prevention (US); National Institutes of Health (US). The Surgeon General’s Call To Action To Prevent and Decrease Overweight and Obesity. Rockville (MD): Office of the Surgeon General (US); 2001. Available at: Accessed: July 6, 2017

[2] Ogden CL, Carroll MD, Mcdowell MA, Flegal KM. Obesity among adults in the United States–no statistically significant change since 2003-2004. NCHS Data Brief. 2007;(1):1-8.

[3] Scialli AR. Teratology Public Affairs Committee position paper: maternal obesity and pregnancy. Birth Defects Res Part A Clin Mol Teratol. 2006;76(2):73-7.

[4] Persson M, Cnattingius S, Villamor E, et al. Risk of major congenital malformations in relation to maternal overweight and obesity severity: cohort study of 1.2 million singletons. BMJ. 2017;357:j2563.


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