Body Mass Index (BMI) and Pregnancy
Unhealthy Weight and Pregnancy (For patients)
Reviewed By Medical Advisory Board
Unhealthy Weight and
Unhealthy weight increases the risk of many
health conditions including hypertension and diabetes, and avoiding the subject
of unhealthy weight gain misses an opportunity to possibly prevent or treat many
weight related illnesses [1-4]. The continued rise in obesity and related
diseases is of global concern .
In 2010, 1 in 4 U.S. women of reproductive age (aged 18-44 years)
The American Congress of
Obstetricians and Gynecologists (ACOG) recommends
that the body mass index (BMI) be recorded for all women at their first prenatal
visit, and that Information concerning the maternal and fetal risks of a very
high BMI in pregnancy should be provided .
The Body Mass Index
The body mass index (BMI) is a measure of someone's weight in relation to their height. The BMI is equal to a person's weight divided by their height
It is calculated
in pounds / Height in inches 2 ) x 703
BMI = (Weight in kilograms /
Height in meters 2)
Body Mass Index Calculator
To calculate you BMI
Enter your weight and height
Select "Calculate BMI" .
The BMI is used to screen persons for weight categories that may lead to
health problems .
Obese- Class I
35 - 39.9
Obese- Class II
40 and above
Obese- Class III
U.S. Obesity Trends 1985–2010
As shown by the maps below the number of persons with an unhealthy BMI has
increased greatly over the last 25 years . The
heaviest BMI groups have increased at the fastest rates.
There are many factors that may be related to the increased prevalence of
obesity over the last 20 years. Among these factors are changes in behavior
known to increase the risk for weight gain such as increased energy intake, reduced rates
of smoking, decreased numbers of hours slept , and
environments that encourage physical inactivity. Some other factors that may be involved include increased pollutants in the
environment that may affect hormones controlling body weight, increased use of
medications that cause weight gain, and an aging population].
Obstetric Complications and BMI
There is good evidence that women with a high body mass index (BMI >
30 ) before or during pregnancy are at greater risk for complications in pregnancy
- Birth defects such as heart defects, neural tube defects, and other
- Difficulty seeing all of the baby's
organs and estimating the baby's weight with ultrasound.
- Difficulty monitoring the baby's
heart rate tracing with the fetal heart monitor
- Gestational diabetes
- Problems having epidural and other anesthesia.
- Delivery by emergency caesarian section.
- Heavy bleeding after delivery.
- Increased risk of forming abnormal blood clots.
- Bladder and kidney infections.
- Wound infection
- Large babies with birthweight above the 90th percentile
- Less likely to have successful vaginal birth after cesarean section
- Increased risk of stillbirth.
The level of these
risks increases as the mother's BMI increases [15-17, 31].
In view of the above risks the American Congress of Obstetricians and Gynecologists
(ACOG) has recommended :
- Preconception counseling for obese women who are planning a pregnancy.
- BMI should be recorded for all women at the initial prenatal visit.
- Information concerning the maternal and fetal
risks of obesity in pregnancy should be provided
- Overweight women (BMI 25-29.9) should be advised to gain no more than 15
to 25 pounds during pregnancy, and obese women (BMI = 30) no more than 15
pounds during pregnancy.
- Obese women should be offered nutrition consultation, and they should be
encouraged to follow an exercise program. This should be continued after
- Screening for gestational diabetes at the initial prenatal visit with
repeated screening later in pregnancy if the results are negative.
- Women with a BMI of 35 or greater who have preexisting medical conditions,
such as hypertension or diabetes, may benefit from a cardiac evaluation.
- Consultation with Anesthesiology prior to delivery.
- Use of compression stockings, hydration, and early
mobilization during and after cesarean delivery should be encouraged.
- Consultation with weight loss specialists before attempting another
The Infectious Diseases Society of America
recommends giving higher doses of prophylactic antibiotics to obese
patients during surgery. Overall, the type of skin incision does not
appear to be associated with wound complications in the obese pregnant woman.
However, vertical abdominal incisions have been associated with increased
operative time, blood loss, and vertical hysterotomy. Wound
complications in obese women undergoing cesarean delivery may be decreased by
closing the subcutaneous tissue in women with at least 2 centimeters of
subcutaneous adipose tissue.
Prophylactic use of subcutaneous drainage has not been
shown to prevent significant wound complications after cesarean delivery.
Promoting A Healthy Lifestyle
The Institute of Medicine (IOM) Guidelines
for healthy weight gain in pregnancy may help women avoid pregnancy
complications such as gestational diabetes, preeclampsia, and cesarean delivery.
Our Pregnancy Weight
Gain Calculator and Prenatal Weight Gain Charts are based on the IOM
guidelines , and may be useful in managing weight gain during pregnancy.
After delivery women at an unhealthy weight should be offered both nutrition consultation
and an exercise program. Although physical activity alone produces only a modest
reduction in weight compared with dieting alone [24-26] regular physical
activity helps maintain weight loss  and results in many health related
benefits in patients even if they lose no weight  .
According to the American College of Sports Medicine patients who have known
coronary, metabolic, pulmonary disease, or signs or symptoms suggestive of
coronary heart disease
may benefit from diagnostic exercise testing before beginning an exercise
program. Most other patients who are obese or overweight can begin with activities such as walking starting with a 5 minute work out and
gradually working up to their goal over many weeks [29,30].
Lastly, breast feeding can help patients to lose the weight
gained during pregnancy, and may also have a small protective effect
against childhood obesity
Unhealthy Weight and Pregnancy (Information
sheet for patients)
Rasmussen KM ed et al. Weight Gain During Pregnancy: Reexamining the
Guidelines Institute of Medicine; National Research Council 2009. p 252, 254
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