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Management of Pregnant Women with Obesity

Dr. Florrie Nga Yui Yu
MBChB, MRCOG, FHKAM (O&G)
Dr. Kwok Yin Leung
MBBS, MD, FRCOG, FHKAM (O&G), Cert HKCOG (MFM)
19 Dec 2020
ABSTRACT
Maternal obesity is a growing health problem that is associated with obstetric and perinatal risks as well as development of obesity and metabolic disorders in offspring. All pregnant women with obesity should be counselled regarding these risks. Reducing obesity before pregnancy is the most effective way to diminish these risks as weight management during pregnancy is a challenge. Proper antepartum, intrapartum, intraoperative, postoperative, and postpartum management are required to reduce adverse maternal-foetal outcomes. Current recommendations on gestational weight gain (GWG) goals, nutrient and vitamin supplements, screening for medical disorders and foetal abnormalities, and management of labour are highlighted in this article. Practice advice on overcoming technical difficulties associated with obesity are discussed.

INTRODUCTION
Over the past 40 years, there has been an increase in the worldwide prevalence of obesity by nearly three times.1 Maternal obesity is associated with adverse obstetric and perinatal outcomes (Tables 1 and 2),2-12 and the likelihood of childhood obesity and metabolic syndrome.13 Excessive amounts of adipose tissue can impair vascular, metabolic, and inflammatory pathways in multiple organs. Maternal hormone levels, altered gene expression, and foetal epigenetic modification may also be altered.14 Perinatal risks are further enhanced by obesity-associated comorbidities. In this article, we will discuss the current recommendations on the pre-pregnancy, antepartum, intrapartum, and postpartum management with a view to improve maternal and perinatal outcomes.

Pre-pregnancy counselling
Obesity can affect reproductive function by affecting oocyte development and endometrial gene expression.15 In early pregnancy, the high concentrations of insulin in women with obesity can cause an alteration of maternal and placental gene expression in relation to mitochondrial steroid hormone production and energy metabolism.16 Reducing obesity before pregnancy is the currently recommended and most effective way to reduce obstetric risks.

Weight loss by even 5% before pregnancy can be beneficial.14 Interventions include diet and exercise. Weight-reducing agents (eg, orlistat and liraglutide) should stop taking these before getting pregnant as these are not approved during pregnancy.17 Women who underwent bariatric surgery should be advised to avoid pregnancy for 12–18 months after surgery to reduce postoperative complications and foetal exposure to the rapid weight loss period.18

It is helpful to screen for comorbidities including chronic hypertension, type 2 diabetes, dyslipidaemia, cardiovascular disease, arrhythmias, osteoarthritis, nonalcoholic fatty liver disease, chronic kidney disease, depression, and obstructive sleep apnoea (OSA).

Diagnosis
Maternal obesity is usually defined as a body mass index (BMI) of ≥30 kg/m2 at the antenatal booking visit.1,14 Weight and height should be measured, as self-reported data may be inaccurate. While BMI correlates well with body fat mass in non-pregnant women, the correlation is not the same in pregnant women because of the significant increase in total body water.19

Pregnant women with obesity should be counselled about the medical and foetal risks (Tables 1 and 2),2-12 and the adverse effects of excessive weight gain. Insulin resistance increases with gestation, and triggers subclinical metabolic dysfunction that progresses to gestational diabetes mellitus (GDM), pre-eclampsia, and macrosomia.14

MPW_Tab-01
MPW_Tab-02

Weight management during pregnancy
The impact of weight reduction may be limited during vs prior to pregnancy. Previous randomized trials showed that the use of metformin during pregnancy can reduce GWG,20-21 but not GDM, large-for-gestational-age foetuses, or adverse neonatal outcomes. Besides, inadequate weight gain is associated with the risk of small-for-gestational-age infants.14

It is difficult to define optimal GWG such that the foetus can develop and grow optimally. Furthermore, optimal GWG may differ with ethnicities and population.25 According to the Institute of Medicine (IOM), pregnant women with BMI ≥30 kg/m2 are advised to gain 4.96–9.0 kg.22 An additional 100 kilocalories (kcal)/day and 300 kcal/day are required before and after 20 weeks of gestation, respectively.23 Women with BMI ≥40 kg/m2 can gain less weight without increasing the risk of adverse pregnancy outcomes, while close foetal monitoring is required.24 Hence, repeated weight measurements during pregnancy is required for women with obesity.

Healthy diet options include low-glycaemic load or low-calorie diet. Advice can be sought from a dietician or a behaviour health counsellor, if necessary. Regular physical activity can protect against excessive GWG, hypertension, GDM, and macrosomia without increasing the risk of preterm birth.26 Regular daily exercise with a gradual increase in moderate-intensity physical activity up to a goal of 30 minutes should be encouraged depending on their medical status, heart rate, comfort, and ability.17 Walking, which can improve aerobic capacity, is preferred by most women; women with back or joint pain may need specific support.

Obesity is associated with vitamin D and iron deficiency, which require adequate supplementation.17 Daily supplementation of elemental calcium 1.5–2.0 g can reduce the risk of gestational hypertension.17 Daily periconceptual supplementation with folic acid 5 mg/day is recommended to reduce the risk of neural tube defects in the foetus.27 Despite the altered microbiome in women with obesity, there is insufficient evidence to recommend probiotic or omega-3 supplementation.17

Maternal assessment and prevention
Screening for OSA in pregnant women with obesity has been suggested. OSA can lead to reduced airflow and hypoxaemia, which can be exacerbated during pregnancy. OSA is also associated with increased risk of pre-eclampsia, eclampsia, cardiomyopathy, GDM, and death.28

The risk of gestational hypertension can be reduced by giving low-dose aspirin (75–162 mg/day) prior to 16 weeks of gestation, if additional risk factors are present.29 A recent multicentre trial has shown that a dose of 150 mg/day of aspirin can reduce preterm pre-eclampsia by >60% in women at high risk.30

Evidence has shown that the insulin precursor myo-inositol reduced the risk of GDM.32 As such, early screening for GDM and retest at 24–28 weeks have been recommended. However, early screening reportedly did not reduce the composite perinatal outcome,31 hence the need for further studies.

Down syndrome screening
Increased maternal BMI is associated with a lower likelihood of prenatal diagnosis of Down syndrome,33 and a higher failure rate for measuring the nuchal translucency. Transvaginal scan may reduce the failure rate.

Obesity is associated with a higher failure rate for noninvasive prenatal testing (NIPT) with cell-free DNA, up to around 25%, because of a higher proportion of low foetal fraction (FF) <4% in maternal plasma.34 This low FF is probably due to an increase in maternal cell-free DNA contribution resulting from adipocyte inflammation and necrosis.34 Options include redrawing maternal blood at a later gestational age, scheduling initial NIPT at a later gestational age, or using serum integrated screening.

Morphology scan
Obesity reduces the odds of detecting congenital anomalies because it reduces the quality of ultrasound images and the likelihood of completing an adequate morphology scan.35 In particular, visualization of the foetal heart, spine, face, extremities, and genitalia is impaired.

Useful tips are listed in Table 3.35 Performing a morphology scan at 22–24 weeks instead of 18–20 weeks may help in assessing foetal structures; however, this may not allow enough time for further investigations like karyotyping before 24 weeks’ gestation if a foetal anomaly is detected. An incomplete scan would warrant timely referral to a specialist. Foetal structures can be assessed by a vaginal scan at 13–16 weeks, albeit with limitations. Foetal magnetic resonance imaging is not used routinely because of its limited availability and cost.

MPW_Tab-03

Foetal monitoring
Accurate dating is important because maternal obesity is associated with a postponement of expected date of delivery by an ultrasound examination at 11–14 weeks’ gestation.36

Maternal obesity is associated with foetal macrosomia. Occasionally, foetal growth restriction (FGR) can result from nutritional deficiencies after bariatric surgery.37 Screening for abnormal foetal growth using serial ultrasound examinations is preferred because symphysial fundal height may overestimate macrosomia and underestimate FGR.28

Serial ultrasound examinations at 28, 32, and 36 weeks for foetal growth and pulsatile index (PI) of the maternal uterine artery are found to be useful to predict adverse pregnancy outcomes.38 When umbilical artery-PI, middle cerebral artery (MCA)-PI, and cerebroplacental ratio (CPR) are used in screening for adverse pregnancy outcomes, appropriate adjustments should be made for BMI because BMI >90th percentile (>36.5 kg/m2) is associated with high MCA-PI and CPR.39 Customized growth curves, and using extrapolation of foetal growth parameters measured between 34+0 and 36+6 weeks to predict birth weight at term, have been proposed.

Given the potential effect of a thick abdominal wall on cardiotocography tracings,40 women with obesity are more likely to present with decreased foetal movement, which is associated with stillbirth and FGR.

Induction of labour
Increased risk of stillbirth associated with maternal obesity is probably related to several risk factors including placental disease, hypertension, infections, foetal or umbilical cord abnormalities, vena caval compression due to maternal supine sleep position, and OSA.2-10,41 Recent evidence suggests induction of labour (IOL) at 39–40 weeks rather than at 41 weeks because the former can reduce macrosomia, neonatal morbidity, neonatal intensive care unit admission, and severe maternal morbidity, and it is cost effective compared with the latter.28,42 For women with a BMI of ≥40 kg/m2, delivery before 38 weeks can reduce perinatal mortality.39 However, the results of failed IOL and reduction of shoulder dystocia are conflicting.42-43

Cervical ripening may require repeated doses rather than a single dose of prostaglandin E2.44 Mechanical ripening with a balloon catheter is an alternative.

Intrapartum monitoring
To avoid aortocaval compression, left lateral labouring position is preferred. Continuous electronic foetal monitoring is recommended for women with a BMI of >35 kg/m2. It may be difficult to monitor uterine contractions or foetal heart rate by manual palpation or with external cardiotocography because of a thick abdominal wall.40 Using intrauterine pressure catheter or foetal scalp electrode is an alternative but is invasive. Electrohysterography and abdominal foetal electrocardiography are new and noninvasive alternatives.

Labour dystocia
Obesity is associated with prolongation of the first stage of labour, higher incidence of labour dystocia, increased risk for Caesarean section.45 Progress of labour should be monitored, and early use of oxytocin has been proposed for slow progress. A higher dose of oxytocin is required to achieve the desired response.43

Despite conflicting evidence regarding the correlation between increasing BMI and increased risk of shoulder dystocia (relative risk, 1.29–2.7),46-47 the use of vaginal operative delivery should be done with caution.

Caesarean section
The increased risk of Caesarean section associated with maternal obesity may be attributable to antenatal complications (hypertensive disorders and macrosomia) and intrapartum complications (foetal heart rate or uterine contractility abnormalities and cephalopelvic disproportion).48 Compared with elective repeat Caesarean delivery, increasing BMI was associated with failed trial of labour after previous Caesarean delivery, greater composite morbidity, and neonatal injury; however, absolute morbidities were small.49

Increasing maternal BMI extends anaesthetic time, failure rate of regional anaesthesia, difficulties in epidural insertion, and endotracheal intubation.52 Antenatal consultation with an anaesthesiologist and early epidural insertion are recommended.53 Epidural top-up can reduce delay to skin incision.52 Combined spinal-epidural anaesthesia can provide a more dense block and allow the flexibility of additional surgical time with a continuous epidural infusion. To avoid hypotension and foetal heart rate decelerations after epidural anaesthesia, adequate volume preloading should be given. To reduce the risk of aspiration, useful interventions include prophylactic epidural, histamine H2 antagonist, sodium citrate with citric acid, metoclopramide, and nothing by mouth during labour.53

For emergency Caesarean sections, increasing BMI prolongs patient-transportation time, anaesthetic preparation time, and skin incision to delivery interval, and thus the decision to delivery interval.50 To reduce difficulty with patient transfer, bariatric lifts, inflatable mattresses, and additional personnel are useful.

Because increasing BMI is associated with decreased maternal plasma and adipose cefazolin concentrations, cefazolin ≥2 g (without allergy) is usually given to reduce postoperative surgical site infection and other wound complications.

In general, the suprapubic transverse incision is the preferred incision to midline subumbilical incision for surgery of the lower abdomen because of decreased postoperative pain and wound dehiscence.51 In extreme obesity, a transverse infraumbilical or supraumbilical incision can offer straightforward access to the lower uterine segment. To facilitate surgical access or exposure, the panniculus can be tapped in a cephalad direction, using self-retaining retractors and long instruments.51 Moist area underneath the panniculus should be avoided because of the risk of wound infection and breakdown.51

Subcuticular closure of adipose layer can reduce wound complications.28 Ligation of large subcutaneous vessels and meticulous surgical technique are useful, but there is insufficient evidence to support the use of subcutaneous drains, negative pressure wound therapy, or a particular wound dressing.28 Keeping the area under the panniculus clean and dry is important.

The wound should be monitored closely for signs of complications including infection, hematomas, and disruption during and after hospitalization. To prevent venous thromboembolism (VTE), early mobilization and adequate hydration are recommended. Physical therapy to assist with ambulation and the use of appropriately fitted pneumatic compression devices are helpful. Thromboprophylaxis with low-molecular weight heparin can be used selectively in high-risk women including BMI ≥40 kg/m2 or two or more persisting risk factors.54

Postpartum
Breastfeeding can protect against childhood obesity. Women with obesity had higher risk of failure to initiate breastfeeding and delayed onset of lactogenesis because of limitations by larger breasts, flattened nipple due to postpartum oedema, associated medical complications, and an early separation of mother and child.55 Additional inpatient and ongoing outpatient support are required.

Women with obesity are less likely to use contraception.56 If there are no comorbidities, progestin-only contraceptives and intrauterine devices can be used, although the former is associated with weight gain and menstrual irregularities.57 Oestrogen-containing contraceptives should be avoided before 6 weeks postpartum in view of the additional risk factors for VTE.

Weight loss before a future pregnancy is the most effective intervention to improve medical comorbidities in women with obesity, and can decrease maternal and foetal risks.28 Behavioural approaches, physical activity, and diet are useful interventions.

Pre-pregnancy obesity, GWG, and postpartum weight retention increases the risk of maternal depression and anxiety.57 Health-related quality of life decreased initially, but returned to baseline within 3 months postpartum.58

CONCLUSION
Weight loss before pregnancy, rather than during pregnancy, is the most effective way to reduce obstetric risks associated with maternal obesity. All pregnant women with obesity should be counselled regarding these risks, optimal GWG, and nutrient and vitamin supplements. Screening for maternal disorders including GDM, pre-eclampsia, OSA, and foetal abnormalities (foetal aneuploidies, anomalies, and macrosomia) are required. A planned peripartum care is needed.

About the authors
Dr Florrie Nga Yui Yu is an Associate Consultant in the Department of Obstetrics & Gynaecology at Queen Elizabeth Hospital, Hong Kong, SAR, China. Conflict of interest: None.

Dr Kwok Yin Leung is an Honorary Consultant in the Department of Obstetrics & Gynaecology at Gleneagles Hong Kong, Hong Kong, SAR, China. Conflict of interest: None.
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