Obesity and Pregnancy Treatment & Management

Updated: Dec 27, 2017
  • Author: Dawn M Palaszewski, MD; Chief Editor: Edward H Springel, MD, FACOG  more...
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Treatment

Antepartum Care

Obese women are at an increased risk of spontaneous abortion (odds ratio [OR} 1.2; 95% confidence interval [CI], 1.01-1.46) and recurrent miscarriage (OR, 3.5; 95% CI, 1.03-12.01) compared with age-matched controls. [8]   Obese women are also at increased risk of most congenital anomalies including neural tube defects (OR, 1.87; 95% CI, 1.62-2.15), hydrocephaly (OR 1.68; 95% CI, 1.19-2.36), cardiovascular (OR, 1.30; 95% CI, 1.12-1.51), orofacial such as cleft lip and palate (OR, 1.20; 95% CI, 1.03-1.40), and limb reduction anomalies (OR, 1.34; 95% CI, 1.03-1.73). The risk of gastroschisis in the neonates among obese gravida, however, is significantly reduced (OR, 0.17; 95% CI, 0.10-0.30). [9]   Obese pregnant women are 40% more likely to experience stillbirth compared with nonobese pregnant women (adjusted hazard ratio, 1.4; 95% CI, 1.3-1.5). [10]

Unfortunately, detection of congenital anomalies by ultrasonography is significantly reduced with increasing maternal BMI. Detection of anomalous fetuses decreases with increasing maternal BMI by at least 20% in obese women compared with normal-weight women. [11]   Obese women are not at risk for fetal aneuploidy, however, obesity can affect screening test performance. First and second trimester serum-based screening tests are adjusted for maternal weight; thus, obesity does not affect test performance. However, accurate nuchal translucency measurement may be more difficult to obtain in obese women. [12]   Cell-free fetal DNA screening is more likely to result in test failure or an inaccurate result in obese women because they may have a lower fetal fraction of the cell-free DNA. [13]  

An increased incidence of dizygotic but not monozygotic twin gestation has been observed among obese gravidas. This association has been attributed to elevated follicle-stimulating hormone levels in obese women. [14]

Early ultrasound should be performed to establish gestational age and determine whether there is a multifetal gestation. As mentioned above, obese women have an increased risk of fetal structural congenital anomalies. Obese women should be counseled about the limitations of ultrasound in identifying structural anomalies. The increased risk for fetal cardiac malformations and the lower detection rates for congenital cardiac malformations with maternal obesity may support the use of fetal echocardiography in these pregnancies unless the detailed ultrasound assessment of the heart is optimal and normal. [15]  Though the approach to fetal aneuploidy screening in the obese gravida is the same as the general population, patients should be counseled on the limitations.  Diagnostic procedures such as amniocentesis and chorionic villus sampling are more technically challenging.

Women should receive counseling regarding potential pregnancy risks associated with obesity including those described above. The primary weight management strategies during pregnancy are dietary control, exercise, and behavior modification.  The goal is to avoid excessive gestational weight gain which is common in obese women. Working with a nutritionist can help patients plan meals for optimum healthy gestational weight gain. Pregnant women with healthy, uncomplicated pregnancies can initiate an exercise program or continue most pre-pregnancy exercise programs. [16]  Almost all drugs prescribed for weight reduction have adverse fetal effects and should not be used during pregnancy. Diet, physical activity, weight gain/loss should all be reviewed frequently throughout pregnancy and the postpartum period.

Compared with normal-weight women, obese women are at increased risk of cardiac dysfunction, proteinuria, obstructive sleep apnea, nonalcoholic fatty liver disease, gestational diabetes mellitus, and preeclampsia.  Many of these are more severe as obesity increases during pregnancy, especially once in the categories of the morbidly obese (40-49 BMI) and more so with the super morbidly obese (BMI 50+). These co-morbidities can be present individually or may be part of an insulin resistance complex. The increased insulin resistance, that is normal during pregnancy, may cause preexisting but subclinical cardiometabolic dysfunction to emerge as preeclampsia, gestational diabetes, and obstructive sleep apnea (OSA). [17]

An association between obesity and hypertensive disorders during pregnancy has been consistently reported. Obese women are more likely to have chronic hypertensive disorders prior to pregnancy. Although these may improve during the early portion of the pregnancy, the underlying pathology will commonly manifest itself in the third trimester.  In a systematic review of 13 cohort studies comprising nearly 1.4 million women, the risk of preeclampsia doubled with each 5 to 7 kg/m2 increase in pre-pregnancy BMI.  This relationship persisted even after adjustment for other confounders such as chronic hypertension, diabetes mellitus, or multiple gestations. [18]  The Medscape article on pregnancy related hypertension can be consulted for further details.

Patients may have occult type 2 diabetes mellitus if screening has not been done within a year or so prior to pregnancy. The prevalence of gestational diabetes mellitus is significantly higher in obese women than in the general obstetrical population and the risk increases with increasing maternal weight and BMI (OR 2.8, 95% CI 2.54-3.08). [19] Routine screening for gestational diabetes is performed at 24-28 weeks of gestation. Early pregnancy screening for glucose intolerance (gestational diabetes or overt diabetes) should be based on risk factors including maternal BMI of 30 or greater, known impaired glucose metabolism, previous gestational diabetes, family history, or PCOS. The best test for early screening is not clear. The testing used to diagnose type 2 diabetes in nonpregnant individuals could be used for early pregnancy screening. Many obstetric care providers start with a 50-gram glucose challenge test. Measurement of hemoglobin A1c also can be used but may not be suitable to use alone because of decreased sensitivity compared with oral glucose tolerance tests. [20]  Some will screen with A1c at new obstetrics visit and if the value is 5.8% or greater consider a GTT or other appropriate additional testing for diagnosis. If the initial early diabetes screening result is negative, a repeat diabetes screening is performed at 24-28 weeks of gestation. The Medscape article on diabetes management in pregnancy can be consulted for further details.

Obstructive sleep apnea may be precipitated or exacerbated during pregnancy and may increase the risk for preeclampsia and gestational diabetes mellitus. [21] Pregnant women with OSA are also at increased risk for eclampsia, cardiomyopathy, pulmonary embolism, and in-hospital mortality. [22] Additional possible adverse pregnancy outcomes include cesarean section as well as having low birth weight, preterm, and small for gestational age infants. [23, 24] Therefore screening for OSA by history should be done and sleep studies ordered as indicated. Obese women should be screened for OSA at the first prenatal visit. Women with suspected obstructive sleep apnea due to reported snoring, excessive daytime sleepiness, witnessed apneas, or unexplained hypoxia should be referred to a sleep medicine specialist for evaluation and possible treatment. Refer to the Medscape article on sleep apnea for screening tools and further information.

In the severely obese patient (BMI>40), there is greater risk for cardiopulmonary dysfunction. Some experts recommend potentially obtaining a baseline echocardiogram and pulmonary lung functions early in pregnancy. However, these are not yet considered a standard of care.

As mentioned previously, if pregnancy occurs before the recommended time frame for women who have had bariatric surgery, closer surveillance of maternal weight and nutritional status as well as serial monitoring of fetal growth will likely be beneficial. It is important to determine the type of bariatric surgery: restrictive (banding) or bypass (Roux-en-Y) since they may present different challenges during the pregnancy and at delivery. Several groups have recommended a broad evaluation for micronutrient deficiencies at the beginning of pregnancy for women who have had bariatric surgery. If there is a deficit then treatment and monitoring should ensue. However there is only “expert” opinion to guide what tests to run, how to supplement and what, if any, clinical complication might occur due to a deficiency in these micronutrients. [25]  If there are not any deficiencies then monitoring every trimester should be considered. [3]  Providers should be aware of bariatric-related operative complications during pregnancy such as anastomotic leaks or bowel obstructions. Medication dosages may also need to be altered such as avoidance of extended release preparations. Alternatives to screen for gestational diabetes should be considered for patients who have had malabsorptive procedures such as a Roux-en-Y gastric bypass due to the dumping syndrome that can occur. For example, these patients could check fasting and postprandial blood sugars for one week. Another option is to check A1c and if 6.5% or greater assume overt diabetes. If A1c is normal, then screen with home blood sugars.

Obese women should be monitored for development of hypertensive disorders during pregnancy or exacerbation of pre-existing hypertensive disease.  Consider baseline quantitative urine protein, creatinine concentration, platelet count, and liver function tests, which can be useful for comparison with laboratory values later in pregnancy if the patient undergoes evaluation for preeclampsia. These baseline labs could be done at the initial obstetrics visit or mid-second trimester (20-24 wks). Obese women with additional risk factors for development of preeclampsia (such as chronic hypertension, multiple gestation, nulliparity, maternal age greater than or equal to 35, family history of preeclampsia, etc.) may benefit from treatment with 81 mg low dose aspirin for prevention. [26]  The Medscape article on hypertensive management in pregnancy can be consulted for further details.

Fetal weight gain is also problematic during pregnancy for an obese patient.  Her co-morbidities may make her more likely to have placental dysfunction with resulting intrauterine fetal growth restriction (IUGR).  However, her insulin resistance and the tendency for obese women to gain excessive weight place the fetus at risk of macrosomia. Because clinical assessment of fetal size by abdominal palpation and fundal height measurement is more challenging, ultrasound assessment of fetal growth every 4-6 weeks is reasonable for most obese pregnant women.  In the setting of severe obesity (BMI 40+), growth scans should be done at least every 4 weeks to identify abnormalities in growth pattern. In the setting of concerning growth they can be done every 3 weeks with interventions for IUGR as indicated.  

 

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Delivery

Timing of delivery

Obesity increases the risk of medically indicated preterm delivery, primarily due to obesity-related maternal disorders such as diabetes or preeclampsia. In a 2010 systematic review, overweight and obese women were at increased risk of induced preterm birth compared with women of normal BMI (relative risk [RR] 1.30, 95% CI 1.23-1.37, five studies) and the risk increased with increasing weight. [27] Whether obesity increases the risk for spontaneous preterm birth is less clear. There is an association between obesity and post-term pregnancy. [28, 29]  The mechanism has not been determined. One hypothesis is that hormonal changes associated with obesity may interfere with the hormonal changes that initiate the onset of parturition.  Another hypothesis is that gestational age calculated from the last menstrual period overestimates true fetal age because obese women tend to be oligo-ovulatory.

Even though stillbirth rates are higher in obese gravidas, there is no evidence showing a clear improvement in pregnancy outcomes with antepartum surveillance, and a recommendation cannot be made for or against routine antenatal fetal surveillance in obese pregnant women.  However, in the morbidly obese woman there is more expert support for routine surveillance starting at 34-36 weeks.

A controversial area is timing of delivery. Induction of the obese patient by the estimated date of delivery is reasonable and does not appear to increase cesarean delivery rate. [30]   Obese women are at increased risk for labor induction anyway due to their increased risk for pregnancy complications. They are also at increased risk for induction failure. A study looking at the effect of maternal obesity on the rate of failed induction of labor found that increasing obesity class is associated with an increased risk of failed induction of labor, from 13% in normal weight women to 29% in class III obese women. Fetal weight and parity also play an important role in the prediction of induction outcome. Limitations of the data in this study prevented further analysis of the exact reasons for the dramatically increased rates of failed induction in obese women compared with normal weight women. [31]

Another area of controversy is the best mode of delivery, especially in the setting of Class III obesity or greater. One retrospective cohort study looked at 661 women with BMI>40 who delivered between 37-41 weeks via planned cesarean section or induction of labor (regardless of eventual delivery route) and were not experiencing spontaneous labor. Composite of maternal morbidity was the primary outcome and a composite of neonatal morbidity was the secondary outcome. Findings showed that in the setting of women with class III obesity a planned cesarean does not appear to reduce overall maternal and neonatal morbidity compared with induction. [32]

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Intrapartum care

External cephalic version is not contraindicated in obese women for fetal malpresentation. However, it becomes increasing difficult with increasing maternal weight – especially in a case of more central distribution. Some studies have found that obesity was associated with a higher failure rate.  It may be easier to attempt a version with the aid of a spinal to allow deeper palpation. [33]  Timing of versions is also challenging since the co-morbidity of diabetes mellitus with polyhydramnios may contribute to a fetus having an unstable lie and result in the fetus converting back to breech if done too soon. 

Intrapartum treatment will be altered for the obese gravida especially the morbidly obese (BMI >40). The labor and delivery unit will need special gowns, beds, doorways and stretchers. Given the increased probability of operative interventions in obese patients, operating tables, lifting equipment, disposable pannus retractors, and surgical instruments that are appropriate for care of obese women need to be readily available. Most of the issues covered in ACOG Committee Opinion of Gynecologic surgery in the obese woman are pertinent to the obese obstetric patient. [34] Fetal monitoring with an external Doppler ultrasound can be difficult and placement of an internal fetal scalp electrode and intrauterine pressure catheter may be useful. To assist in being sure that the entire unit is aware of patients who have class III obesity or worse so that they can be prepared to modify management or address the challenges in an emergency with these patients, the “labor board” could include a column with information regarding obesity.  In this way, the anesthesia service and others on the unit can be made aware of the possible need for assistance with a complicated case.  

Anesthesia consultation early in labor is encouraged, especially with BMIs of 40+, as there are many challenges posed by maternal obesity. Even if a patient does not plan on having a laboring epidural, anesthesia involvement in patients with higher BMI is common so early brief consultation can help everyone be prepared for emergent needs.  Epidural or spinal anesthesia may be technically difficult to place due to body habitus and loss of landmarks. Early placement of epidural catheter increases the success of being able to utilize regional anesthesia in the setting of an urgent cesarean. General anesthesia could be problematic because of difficulties with endotracheal intubation due to excessive tissue and edema, patient positioning, or a heavy pannus compromising ventilation. The necessary equipment will need to be available (blood pressure cuffs, venous access, fiberoptics for intubation). Patients with obstructive sleep apnea are at risk of additional challenges for both regional and general anesthesia. [34]

Increasing BMI is associated with increased incision-to-delivery time, which may increase neonatal morbidity, particularly in emergency situations. [35]  It is important not to wait until the last moment to transport patient to OR, place epidural catheter etc., especially in the setting of morbid obesity and super morbid obesity.  

The median duration of labor from 4 to 10 cm is significantly longer for both overweight and obese women compared with normal weight women (7.5, 7.9, and 6.2 hours, respectively). [36]  This must be considered prior to diagnosing a failed induction or arrest of stage 1. Duration of the second stage of labor does not appear to be affected by increasing BMI. [37]

Studies have shown that a trial of labor after cesarean section is less likely to be successful in increasingly obese women.  Operative vaginal delivery is also more likely if a woman is obese, control 10.5%, obese 8.5%, and morbidly obese 11.1%. [38]

Macrosomia or birth weight >4000g is more common in the infants of obese women and a risk factor for shoulder dystocia. For moderate obesity, the shoulder dystocia OR is 1.51 (95% CI 1.32-1.74) compared to non-obese women. [19]  

For moderate obesity, the risk of postpartum hemorrhage is higher, OR 1.12 (95% CI 1.02-1.22) compared to non-obese women. [19]  Given the increased risk of hemorrhage and the increased difficulty in acquiring IV access as BMI increases, a provider should evaluate an obese patient on labor and delivery for a large bore IV (16 gauge) or placement of 2 IVs that are secured.  In the super morbidly obese patient a longer than typical angiocatheter or central line placement may be necessary to ensure adequate IV access in the setting of a massive hemorrhage.  Hemoglobin/hematocrit should be noted on admission to the Labor & Delivery unit and all labor stages should be managed to minimize hemorrhage risks.

Numerous studies report an increased risk of cesarean delivery among overweight and obese women compared with normal-weight women. [39] The optimal skin incision for primary cesarean delivery in patients with a BMI greater than 35 has not been determined. [17]  Much of this depends on the distribution of the weight and the height of the patient.  On admission to the Labor and Delivery unit consideration should be given to location of a surgical incision should a cesarean section be necessary in all patients who are morbidly obese.  An appropriate dose of prophylactic antibiotics should be administered based on maternal weight. Some recommendations based on general surgical procedures would suggest a 2g prophylactic cefazolin dose for women who weigh more than 80kg (175 lbs.), with an increase to 3g for those who weight more than 120kg (265 lbs.). [40]  Few studies have specifically addressed the question of weight-based dosing for antibiotic prophylaxis at the time of cesarean delivery.  These have had mixed results.  An additional suggested strategy is a second dose of antibiotics 4 hours after the first.  The obese gravida is at higher risk for postpartum infection regardless of mode of delivery, including wound, episiotomy, or endometritis.  Various strategies have been tried to minimize these.  Good glucose control, strict aseptic technique, and appropriate antibiotic use have helped to decrease the infection rate. [41] Routine use of subcutaneous drains, delayed skin closure at cesarean section, or use of incisional wound vacuum-assisted closure (VAC) have not demonstrated a decreased infection rate. In the setting of a BMI of 50+ over 30% of women had a wound infection typically being diagnosed at 6-12 days post-surgery. [42, 43]

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Postpartum concerns

In one review, the risk for postpartum venous thromboembolism in women with class I, II, and III obesity was OR 2.5, 2.9, and 4.6, respectively, compared with women whose BMI was normal. [44]  Pharmacologic thromboprophylaxis should be considered in addition to pneumatic compression devices.  Use of pharmacologic thromboprophylaxis and duration of postpartum prophylaxis depend on several patient-specific factors.  For instance, patients with preeclampsia, fetal growth restriction, infection, and emergency cesarean delivery are at increased risk of venous thromboembolism. [45]   Any of these risks in the setting of BMI of 40+ should prompt a consideration for thromboprophylaxis postpartum. [46]  

Obese women are prone to difficulty with lactation. Consultation with a lactation specialist while in the hospital and access after discharge is helpful. [47]

Close follow up postpartum for the first 6 weeks is often indicated especially in the setting of operative delivery or intrapartum co-morbidities.  Attention needs to be given to the maternal co-morbidities that were present at the onset of the pregnancy or developed during the pregnancy to see if they persist or resolve.  Ongoing primary care to help with management of persistent morbidities such as diabetes, hypertension, fatty liver as well as weight loss is important.

 Importantly, children of obese women have a predisposition to obesity later in their life. Postpartum women should be supported in their efforts to lose gestational weight gain, avoid postpartum weight gain, and achieve a healthy/healthier body mass index. A woman with a BMI of 35 + may not feel it is possible to achieve a BMI < 30.  Telling a patient that the loss of 10% of her body weight has significant health benefits can be helpful as it may be seen as an achievable goal by the patient.   Interpregnancy weight gain or interpregnancy weight loss can affect risks in a subsequent pregnancy. 

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Approach Considerations

A series of considerations for the management of the obese patient (Open Table in a new window)

Antepartum Care

Initial OB visit

   

< 40 BMI

BMI 40+

 

H&P screening for maternal co-morbidities

 

Consider maternal echocardiogram, pulmonary function testing,

sleep study

 

Laboratory testing

+/- Thyroid function tests 

Thyroid function tests

   

A1c if not diabetic [20]

A1c if not diabetic with GTT as indicated [20]

 

U/S

First trimester dating/rule out multiples

First trimester dating/rule out multiples

 

Counsel on weight gain

11-20 lbs. total

< 15 lbs. and none is acceptable in the setting of excellent nutrition

 

Exercise

Aerobic activity minimizing high impact

Walking and swimming (likely best tolerated)

 

Genetic Counseling/Screening

   
 

           Aneuploidy – no different

Serum analytes OK

Serum analytes OK

 

         

NT can be difficult [12]

NT very challenging [12]

   

NIPS – may have test failure more commonly

NIPS may not perform well especially early

 

           Patient counseling regarding              screening

Test performance similar to non-obese patients

Testing performance is compromised by obesity and this is “dose” based

Prenatal Care through 24 weeks gestation

 

Ultrasound

Detailed anatomy scan at 20 wks

Detailed anatomy scan at 20 wks

     

Possible fetal echo at 24 wks [15]

 

Weight

Closely monitor and counsel patient

Closely monitor and counsel patient

Prenatal Care 24 – 36 weeks gestation

 

Labs

1 hr 50 gm glucola

challenge / Hct

1 hr 50 gm glucola challenge/Hct

 

Ultrasounds

Serially for growth q 4-8 wks until delivery

Serially for growth q 3-4 wks until delivery

 

Frequency of visits for screening – (development of complications will require more frequent visits)

Q 4 wks until 28-32 wks then q 2 wks until 36 wks then q 1-2 wks until delivery

Q 4 wks until 28 wks then q 1-2 wks until 36 wks then weekly

 

Weight gain

Closely monitor and counsel patient

Closely monitor and counsel patient

 

Antenatal surveillance (NST / AFI)

Only as done for non-obese patients

Potentially start at 32 wks in super morbid obesity (BMI 50+)

 

Anesthesiology

 

Consider anesthesia consult, Evaluate L&D unit to see if they have the equipment to handle patient’s size

 

TOLAC counseling

Per routine for non-obese patients

Factor in lower success rate with elevated BMI

Prenatal Care 36+ weeks

 

Antenatal surveillance

FKC and other only as indicated for non-obese patients

Potentially consider NSTs/AFI starting at 34-36 wks  if not started sooner due to complications

Delivery /Intrapartum Care

 

Timing of delivery

By 41.0 wks but 40 wks reasonable and even 39 wks if excellent Bishop score [30]

Some experts recommend delivery at 39 wks if not already delivered for co-morbidities [30]

 

Anesthesiology

Consult as indicated for non-obese patients

Alert them for anesthesia assessment when patient admitted even if not anticipating need for anesthesia services

Can assess if regional anesthesia is an option or not

 

Unscheduled cesarean section for indications

Routine management [35]

Consider in labor management given the inability to do a truly emergent cesarean section [35]

 

Incision type for cesarean section

Routine management [17]

Consider patient body habitus

 

Antibiotic coverage for cesarean section

Routine management [40]

Consider increased dose based on weight and consider repeat dose 4 hours post initial dose [40]

Postpartum Care

 

DVT prevention

Similar to non-obese patients [45]

Consider use of anticoagulation meds especially if other risk factors for DVT such as cesarean section, preeclampsia, infection, etc. [45]

 

Difficulty with lactation

Lactation consultation in hospital and after discharge [47]

Lactation consultation in hospital and after discharge [47]

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