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Maternal–Foetal Medicine
Obesity, Diabetes and the Risk of Macrosomia
Nir Melamed
1
and Moshe Hod
2
1. Physician; 2. Professor and Director, Division of Maternal–Foetal Medicine, Helen Schneider Hospital for Women, Rabin Medical Centre, Tel Aviv University
Abstract
Maternal obesity, diabetes and pregnancy weight gain are independent risk factors for foetal overgrowth. Data regarding the relative
contribution of each of these factors are controversial. Nevertheless, owing to its increasing prevalence, maternal obesity probably exerts
a greater impact on the prevalence of macrosomia, especially when diabetes is well controlled. Reducing the rate of macrosomia may be
an ideal form of primary prevention of the development of obesity and diabetes later in adult life. Weight reduction prior to pregnancy and
strict glycaemic control may reduce the risk of macrosomia and interrupt this vicious cycle. Further studies are needed to determine the
optimal weight gain during pregnancy for obese women, as current recommendations may contribute not only to the development of
macrosomia, but also to the global epidemic of obesity.
Keywords
Obesity, weight gain, diabetes, macrosomia, large for gestational age (LGA)
Disclosure: The authors have no conflicts of interest to declare.
Received: 15 December 2008 Accepted: 9 February 2009
Correspondence: Moshe Hod, Director, Division of Maternal–Foetal Medicine, Helen Schneider Hospital for Women, Rabin Medical Center, Sackler Faculty of Medicine,
Tel Aviv University, Petah-Tiqva, 49100, Israel. E:
mhod@clalit.org.il
Foetal macrosomia has long been associated with an increased risk of of 30 or greater. Obesity is further classified by BMI into class I (30–34.9),
Caesarean section, shoulder dystocia and birth trauma.
1,2
More recently, class II (35–39.9) and class III (greater than 40).
17,23
Some studies use
evidence has accumulated linking foetal macrosomia to an increased other measures to define obesity, including pre-pregnancy weight,
24
risk of obesity and diabetes in early adult life.
3–9
This finding is similar to weight at delivery
16,25,26
and waist-to-hip ratio (WHR).
27
the observations of Barker in growth-restricted foetuses,
10
and thus
implies a U-shaped curve relationship between birthweight and the risk Obesity and the Risk of Macrosomia
of adult disease.
6
Among the many factors that have been associated Maternal obesity has been shown to be associated with an increased
with exaggerated foetal growth,
11–13
maternal obesity, excessive maternal risk of macrosomia and large-for-gestational-age (LGA) infants
24,28–35
weight gain during pregnancy and diabetes have been shown to play independent of other factors that affect foetal growth, including pre-
important roles.
14–16
However, the effect of each of these factors, as well gestational
14,15,36
and gestational
12,14,29,34,37
diabetes (PGDM and GDM,
as their relative contribution to the risk of foetal overgrowth and respectively). The magnitude of effect of obesity on the risk of
macrosomia, remains controversial. The purpose of this article is to macrosomia in normal (non-diabetic) pregnancies varies considerably
review current information regarding the relative contribution of between different studies and has been reported to range from 1.4- to
maternal obesity and diabetes to the risk of foetal macrosomia. 18-fold.
14,22,30,38–41
Several studies have shown a continuous relationship
between maternal obesity and the risk of foetal macrosomia/LGA
Maternal Obesity infants, so the higher the BMI, the higher the risk.
14,15,35,42–44
In a large
Epidemiology multicentre study of more than 16,000 patients, class I and class II
Obesity has become a worldwide epidemic.
17
The World Health obesity patients were at increased risk of foetal macrosomia (odds ratio
Organization’s (WHO’s) latest reports indicate that in 2005 approximately [OR] 1.7 and 1.9, respectively).
35
In another population-based study, the
1.6 billion adults were overweight and at least 400 million adults were risk of delivering a macrosomic infant increased with each level of
obese. As the prevalence of obesity is increasing, so is the number of increasing BMI, using BMI <20 as the reference group (normal weight OR
women of reproductive age who are overweight and obese. In the US, 1.2, overweight OR 1.5, obesity OR 2.1).
42
the incidence of obesity among pregnant women ranges from 18.5 to
38.3%, according to different reports.
18–22
Whether overweight (rather than obese) women are also at an increased
risk is unclear. In a retrospective cohort study of 12,950 pregnancies,
Definitions being overweight was an independent risk factor for LGA infants (OR
The WHO defines being underweight as having a body mass index (BMI) 1.2), although the risk associated with obesity was higher (OR 1.6).
15
In
≤18.5, being of a normal weight as having a BMI of 18.5–24.9, being contrast, in a prospective study of women with PDGM (n=196) and GDM
overweight as having a BMI of 25–29.9 and being obese as having a BMI (n=428), being overweight was not associated with an increased risk of
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