Obesity in Pregnancy —(GTG # 72)

This blog post is a summary of GTG guideline # 72 published in November 2018.

Obesity in pregnancy is associated with risks to both mother and fetus. The points in this post are exclusively summarized from latest guideline and some additional points from various sources. GTGs are a must for the exam. It is strongly recommended to go through the original document which is available free on the RCOG website.

GTG # 72 Care of Women with Obesity in Pregnancy

Introduction 

• Obesity is increasing in UK population 9-10% in 1990s : 16-19% in 2000s
• One of the most commonly occurring risk factor in obstetrics 
• Pregnancy:
• Normal BMI 47%
• Obese 21%

Classification of adults according to BMI (Source GTG)
Classification	BMI (kg/m2)
Underweight	< 18.50
Normal range	18.50–24.99
Overweight	≥ 25.00
Preobese	25.00–29.99
Obese class I	30.00–34.99
Obese class II	35.00–39.99
Obese class III	≥ 40.00

Risks of Obesity
Mother	Fetus
Miscarriage Gestational Diabetes (GDM) Hypertensive Disorders (PIH/PET) Venous Thromboembolism (VTE/PE) Induced Labour (IOL) Dysfunctional or Prolonged Labour Cesarean Section Anaeesthetic Complications PPH Fetal monitoring challenging  Difficulty in breastfeeding (both initiation & maintenance)	Congenital anomalies Prematurity Still Birth Macrosomia Neonatal Deaths Increased Obesity/ Metabolic disorders in childhood

• High pre-pregnancy BMI associated with small but statistically significant increase in severe maternal morbidity and mortality
• MBRRACE-UK 2015

• 30% of women who died were obese
• 22% women were overweight

• CEMACH 2003-5 recommended: women with BMI ≥30 kg/m2 should have prepregnancy counseling

Pre-pregnancy care

Primary care settings

• Should ensure to optimize weight before pregnancy in women of childbearing age
• Advice on weight and lifestyle during preconception counseling or contraceptive consultation 
• Measure weight and BMI
• Weight loss in between pregnancies reduces stillbirth, hypertensive disorders / macrosomia and improves chances of VBAC
• BMI ≥30 kg/m2 
• advised to take folic acid (5mg), starting at least one month before conception and continue till 1st trimester because of ↑ risk of NTD
• BMI ≥27 kg/m2 
• less likely to use nutritional supplement/folate in diet 
• folate levels are low even after controlling folate intake
• Vitamin D
• Prepregnancy BMI is inversely associated with serum Vit-D in pregnant women
• BMI ≥30 kg/m2
• ↑d risk of Vit-D deficiency
• cord serum Vit-D levels→ lower
• In UK women at risk of Vit-D deficiency 

• 1/4 aged 19-24 yrs 1/6 aged 25-34 yrs

• Vit-D supplements in single continued dose ↑ serum 25-hydroxyvitamin D at term and may reduce risk of low birthweight, preterm birth & pre-eclampsia
• If calcium and Vit-D combined → risk of preterm birth increased 
• Cholecalciferol 1000 iu/day is sufficient & a safe dose

Antenatal Care

• BMI ≥30: Must have multidisciplinary care, documented antenatal consultation about intrapartum risks
• BMI ≥35 : Deliver in consultant-led unit (CLD)
• At Booking Visit: Weight, height and BMI should be calculated for ALL women & recorded in handheld notes + electronic systems
• Consider re-weighing in 3rd trimester for women with obesity
• Measured weight is preferable but self-reporting is cost-effective/practical
• Optimal gestational weight gain → No consensus. Focus on healthy diet 
• Counseling regarding
• risks should be given wherever possible
• diet and exercise advice by appropriately trained professionals
• Anti-obesity or weight loss drugs are not recommended for use in pregnancy.

• Orlistat: no increase in major malformation risk
• Topiramate: linked to oral clefts (OR 6.26)
• Topriamate and Phentermine: excreted in breast milk and not recommended during lactation
• Lorcaserin: contraindicated in pregnancy

Risk assessment

Anaesthesia Risks 

• BMI ≥40 kg/m2:
• Refer to obstetric anaesthetist for antenatal assessment
• Obesity → significant risk factor for anaesthesia-related maternal mortality
• Difficulties in airway management, bag mask ventilation/ failed intubation, higher risk of desaturation/ postoperative atelactesis; significantly higher gastric volumes in laboring women
• ↑ decision-delivery time in women who need cat 1/ 2 C/S
• Each women to be given labour analgesia advice
• UKOSS data: 1/4 maternal cardiac arrest→ related to anaesthesia. Out of those 75%→ obese
• A cohort study: epidural resite rates in class III obese 17% vs 3% in controls

Pressure Sores

• Risk factors → immobility & BMI ≥40
• Documented risk assessment in 3rd trimester for women with booking BMI of ≥40
• Reassessment → if there is change in clinical status
• If found high risk → should have plans for skin assessment, skin care, repositioning frequency and pressure redistributing devices 

Gestational Diabetes (GDM)

• Booking BMI ≥30 → should have screening for GDM
• Obesity + GDM → 3-fold ↑ risk of congenital anomalies
• GDM → ↑ risk of developing type II DM (RR 7.43) later in life
• maximum risk within first 5 years following GDM pregnancy
• After 5 years → plateau

Hypertension

• Use appropriate sized cuff & document (size) in records. More chance of error if too small cuff used
• ≥Class II obesity have↑ risk of PET than women with normal BMI
• Risk ratio compared with normal BMI

• Overweight 1.70
• Obese 2.93
• Severely obese 4.14

• With >1 moderate risk factor (BMI ≥35, primiparity, maternal age > 40yrs, family h/o of PET and multiple pregnancy)— women may benefit from aspirin 150 mg daily from 12 wks till delivery of baby (NEW)
• Enhanced benefit if aspirin taken at night 
• Risk of recurrence PET in next pregnancy increases linearly with increasing BMI

VTE

• BMI ≥30 associated with ↑ risk of VTE
• Individualized risk assessment at first antenatal visit, during pregnancy (if admitted or intercurrent problems), intrapartum and postpartum (GTG 37a and 37b)
• With obesity risk of PE greater than DVT
• In women ≥90 kg on therapeutic doses of LMWH measure routinely peak anti-Xa activity
• Weight-based dosing of LMWH→ superior to fixed dosing in reversing increased tendency of VTE in class III obesity

Mental Health

• BMI ≥30: ↑ risk of mental health problems & should be screened
• Higher risk of depression 
• During pregnancy

• Obese 33% overweight 28% normal weight 22%

• Postpartum 

• Obese 13% overweight 12% normal weigh 10%

• Obese women → higher odds of antenatal anxiety (OR 1.41)
• Lifestyle intervention (diet/ physical activity advice) → effective in reduction of gestational weight gain, but conflicting results on depression and anxiety levels

Antenatal Screening

• BMI ≥30 →  ↑ risk of structural anomalies. Highest OR of spina bifida (OR 2.24)
• Even in absence of GDM obese pregnant are at ↑ risk of congenital cardiac defects (OR 1.18)
• ALL women to be screened for Down’s Syndrome (as per national guidance)
• In obese: TVS can be considered to measure nuchal translucency (NT) if difficult on abdominal USG
• Maternal BMI has significant impact on success of obtaining accurate NT measurements. Additional time needed; still there is ↓ chance of success and need for repeat visit
• Proportion of pregnant women who complete first trimester screening is inversely proportional to their BMI
• If first trimester screening not successful → offer second trimester screening with serum markers
• Non-invasive prenatal testing (NIPT) has its limitations & less effective in obese due to ↓ of free fetal DNA in maternal serum with increasing weight 
• May offer diagnostic tests due to limitations of screening test, after full counseling
• CVS or amniocentesis risk of fetal loss

• BMI 30-40 : No increase
• BMI ≥40:  ↑ loss rates (aOR 2.2)

• Screening and diagnostic tests for structural anomalies in obese
• should be offered despite their limitations
• ↑ risk of missed antenatal diagnosis for fetal anomalies (aOR 0.7)
• lower sensitivity and higher false-negative rate of detection for multiple aneuploidy markers 
• extra time needed for anomaly scans, repeat scans. 
• repeat scans at a later gestation can improve identification of cardiac structural anomalies

Fetal Surveillance

• To improve prediction of SGA serial measurement of SFH from 24 wks is recommended
• Women with BMI ≥35 should be referred for serial assessment using USG
• Obese women are at ↑ risk of prolonged pregnancy, IOL and stillbirth
• Successful vaginal birth after IOL in obese

• primigravida 60%
• multiparous 90%

Labour & Birth

• Multidisciplinary/ individualized approach considering woman and her partner’s views
• Informed discussion with her obstetrician, midwife/ anesthetist and documented in notes
• Multiparous + low-risk may be offered choice for planning birth in (midwifery-led units ) MLUs with clear referral pathways for early recourse to CLUs if complications 
• Obesity associated with increased

• IOL OR 1.70
• Augmentation of labour aOR 1.26
• Intrapartum C/S aOR 1.52
• Shoulder dystocia OR 2.9
• PPH OR 1.39
• Additional analgesia in labour request aOR 1.20 for epidural

• Booking BMI ≥35: planned labour/ birth in an obstetric unit (CLU)
• Booking BMI 30-35: individualized assessment for place of birth
• Discussion of labour and birth → before 36 wks of gestation (including labor plan, management of pain/prolonged pregnancy)
• Healthy nulliparous obese women → increased risk of interventions like early hospitalization, ARM, epidural analgesia, IOL and augmentation of labour
• Active management for 3rd stage → recommended

Induction of Labour (IOL)

• Elective IOL at term in obese

• may decrease chance of C/S, macrosomia, mean birthweight, fracture cases & shoulder dystocia
• no difference in odds of operative vaginal birth, lacerations, brachial plexus injury or respiratory distress syndrome

• IOL may be considered if macrosomia identified confidently
• Non diabetics + macrosomia → IOL is not associated with reduced shoulder dystocia, but does reduce risk of fetal fractures 
• Fetuses in IOL group are at ↑ risk of (as compared to expectant mx group)
• raised bilirubin >250 mmol/l  (9% vs 3% — OR 3.03)
• phototherapy (11% versus 7%— OR 1.68)

Casearean Section (C/S)

• Decision of planned C/S for obese women → by MDT taking into consideration co-morbidities, antenatal complications & her wishes
• Risk of C/S → increased by 50% in overweight; more than doubled in obese
• Nulliparous + Unfavorable Cervix → more likely failed IOL
• Class III obesity: planned C/S → not associated with reduced morbidity as compared to IOL
• No change in risk of C/S with IOL

Vaginal Birth after C/S (VBAC)

• Booking BMI ≥30 women → individualized decision for VBAC. 
• Obesity→ risk factor for unsuccessful VBAC

• Successful VBAC : 54% obese vs 70% with normal BMI

• Booking BMI normal but later obese BMI at birth → reduced chances of successful VBAC
• Class III obesity → increased rates of uterine rupture during labor trial and neonatal injury. Emergency C/S → increased risk of serious maternal morbidity due to anaesthetic &  difficult operative deliveries 

Place of birth 

• Obese women → significantly higher risk of shoulder dystocia, emergency C/S & atonic PPH after vaginal but NOT C/S birth
• Babies of obese mothers → up to 1.5 times more likely to be admitted in NICU than babies of normal weight mothers 
• Class III Obese  admitted in labour ward
• Inform On-duty anaesthetist 
• Early epidural 
• Continuous midwifery care with additional measures to prevent pressure sores & fetal monitoring
• Early Venous access established. Consider siting second cannula

Delivery

• BMI ≥30: Active management of 3rd stage of labour (very important) as it decreases

• risk of PPH, postpartum anemia and need for blood transfusion
• reduced incidence of prolonged 3rd stage 
• reduced use of therapeutic oxytocic drugs 

• During C/S

• Vital to have additional experienced assistant
• ≥Class I obesity → prophylactic antibiotics at the time of surgery (aOR of 2.24 for wound infection in obese vs healthy weight women)
• >2cm subcutaneous fat → suture subcutaneous tissue space to ↓ risk of wound infection/separation
• No clear evidence to support one surgical approach over another
• Insufficient evidence for use of negative pressure dressing in obese

Postnatal care and follow-up after pregnancy

• BMI ≥30 → appropriate specialist advice/ support for breastfeeding benefits, initiation and maintenance
• Maternal obesity associated with
• delay in lactogenesis, lower breast-feeding initiation rates, earlier cessation of lactation and earlier introduction of solids
• Multifactorial like women’s perception of breastfeeding, difficulty with correct position and possibility of impaired prolactin response to suckling
• Breastfeeding support + education → associated with higher breastfeeding initiation rates  and sometimes longer durations of breastfeeding as well
• Contraception advice should be according to FSRH. Obesity should be considered in making the choice
• ≥Class I obesity at booking → continue advice after delivery regarding nutrition, exercise and lifestyle
• Support women to lose weight postpartum and offer referral to weight management services if available 

Management of pregnancy after bariatic surgery

• Wait for minimum 12-18 moths after bariatic surgery to get pregnant
• Women with bariatic surgery have 

• ↓ odds of GDM, hypertensive disorders & macrosomia
• increase odds of SGA (OR 2.16), preterm birth, admission to NICU; maternal anemia/ nutritional deficiencies

• Overall obstetrics outcome → better after bariatic surgery in class III obesity women
• Women with previous bariatric surgery should have

• Consultant-led care
• Nutritional surveillance & screening for deficiencies
• Referred to dietician for advice

Additional Points 

• Weight loss of at least 4.5 kg before next pregnancy reduces risk of developing GDM by up to 40%
• Higher dose of folic acid reduces the subsequent NTD-affected pregnancy by 72%
• Pre-pregnancy BMI → inversely associated with serum Vit-D concentrations
• Epidural re-site rates → high with increasing BMI (Up to 42%)
• Booking BMI ≥ 40 → documented assessment in 3rd trimester to determine manual handling requirements for child birth and consider tissues viability issues
• BMI ≥30 → encourage mobilization as early as practical after birth
• Both obesity & immobility → independent risk factors for VTE. Combination → greater risk
• Raised booking BMI → associated with 50% increase in risk of pre-eclampsia (PET)
• Booking BMI ≥35 → doubled pre-eclampsia risk
• Obesity alone not an indication for IOL
• Operating theatre staff alerted → women >120kg for operative intervention in theatre/ appropriate operating table
• Obstetrician & anesthetist at speciality training year 6 and above or with equivalent experience in non-training post → informed and available for BMI ≥40 during labor and delivery
• If trainee obstetrician not competent signed-off  for C/S→ Consultant on-call for labour ward should be available
• Diet-treated GDM → 41% type 2 DM median of 10 yrs
• Pre-pregnancy overweight & obesity → significant risk factors for type 2 DM 
• BMI ≥30 with GDM → annual screening for cardio-metabolic risk factors, offer lifestyle & weight management advice
• Prolonged pregnancy incidence
• Normal weight → 22%
• BMI 30-34 → 30%
• BMI 35-39 → 32%
• BMI ≥40 → 34%