Obesity in Pregnancy
(GTG 72 - Nov 2018)

Classification of BMI
Underweight: <18.5 Normal: 18.5-24.99 Overweight: =/> 25
Pre-obese: 25-29.99
Class I obesity: 30-34.99
Class II obesity: 35-39.99
Class III obesity: =/>40

Epidemiology

21.3% of antenatal population obese

47.3% of pregnant women have normal BMI

Pre-Conception Counselling

Rise in prevalence: 9-10% to 16-19%

Risks of Obesity

Antenatal Screening for Anomalies

Measure weight and BMI: At booking and in the 3rd trimester

Women with BMI =/> 30 should receive information and advice about risks of obesity during pregnancy and childbirth, and be supported to lose weight

Maternal

  1. Miscarriage
  2. Caesarean delivery (risk increases 50% in overweight, and more than doubles in obese)
  3. Initiation and maintenance of breastfeeding; physiological delay in lactogenesis
  4. Pre-eclampsia and hypertensive disease in pregnancy
  5. Gestational diabetes (3-fold)
  6. Anaesthetic complications
  7. Postpartum haemorrhage
  8. Wound infections
  9. Maternal mortality
  10. Difficulty in assessment of fetal size, presentation, and external fetal monitoring
  11. Vitamin D deficiency
  12. Poor ultrasound visualisation of baby and difficulties in fetal surveillance and screening for anomalies
  13. Development of pressure sores due to immobility
  14. Venous thromboembolism
  15. Mental health problems: Depression, anxiety, eating disorders, serious mental illness
  16. Prolonged pregnancy
  17. Increased interventions and intrapartum complications: Induction and augmentation of labour, ARM, slow progress, emergency Caesarean section, shoulder dystocia, epidural analgesia, unsuccessful VBAC

Benefits of weight loss

  1. Reduces risk of stillbirth
  2. Reduce risk of hypertensive complications
  3. Reduces risk of fetal macrosomia
  4. Increases chance of successful VBAC

Increase in severe maternal morbidity and mortality - Adjusted rate difference per 10,000 women compared with normal BMI: 24.9 (Class I), 35.8 (Class II), 61.1 (Class III)

Fetal

  1. Congenital anomalies: Neural tube defects, spina bifida, cardiovascular anomalies, congenital cardiac defects, septal anomalies, cleft lip and palate, anorectal atresia, hydrocephaly, limb reduction
  2. Stillbirth
  3. Prematurity
  4. Macrosomia
  5. Neonatal death
  6. Neonatal admission: Up to 1.5 times more likely
  7. Increased risk of developing obesity and metabolic disorders in childhood

Advise 5mg folic acid supplementation, starting 1 month pre-conception and continuing during the first trimester

Advise 10mcg of vitamin D daily: May reduce risk of low birthweight, preterm birth, and pre-eclampsia (note risk of preterm birth increased when calcium and vitamin D are combined)

Information during Pregnancy

No optimal gestational weight gain, focus on healthy diet

Anaesthetic assessment for BMI =/> 40

  1. Risk for anaesthesia-related maternal mortality
  2. Higher risk of epidural resiting, difficulties with airway management, difficult bag mask ventilation and failed intubation, desaturation, post-operative atelactesis, higher gastric volume, and increased decision-delivery time in category I and II Caesarean sections.

Anti-obesity or weight loss drugs not recommended:

  1. Orlistat: Lipase inhibitor that inhibits absorption of dietary fats.
  2. Phentermine/topiramate: Promotes appetite reduction/suppression, and decreases food consumption (increased satiety). Use is linked to oral clefts, transmitted in breast milk.
  3. Lorcaserin hydrochloride: Serotonin receptor agonist selective for the receptor involved in regulation of appetite. Promotes satiety promotes weight loss through decreased food consumption. Use is linked to low birthweight.

Dietetic advice regarding pregnancy diet and weight gain

25% maternal cardiac arrests related to anaesthesia; 75% of these obese

Tissue viability and pressure ulcer risk assessment using a validated scale for BMI =/> 40

Screen BMI =/> 30 for gestational diabetes: 3 fold increased risk of GDM, obese women with GDM 3 fold increased risk congenital anomalies

Advise 150mg aspirin from 12 weeks to delivery in women with >1 moderate risk factor:

  1. BMI =/>35 (increased risk of pre-eclampsia)
  2. First pregnancy
  3. Maternal age >40 years
  4. Family history pre-eclampsia
  5. Multiple pregnancy

Higher risk of depression in obese women:

  1. Pregnancy: Obese 33%, overweight 28.6%, normal 22.6%
  2. Postpartum: Obese 13%, overweight 11.8%, normal 9.9%

Screen BMI =/> 30 for mental health problems

Transvaginal ultrasound: Consider in women where nuchal translucency measurements are difficult to measure transabdominally

Non-invasive prenatal sceening: May be less effective as free fetal DNA fractions decrease with increasing maternal weight

Offer 2nd trimester screening if unsuccessful 1st trimester

Diagnostic testing: Higher rates of miscarriage in women with class III obesity following amniocentesis

Screening for structural anomalies: Increased echogenicity of adipose tissue and increased absorption of ultrasonic sound beam by abdominal fat results in reduced image clarity and poor image quality. This leads to increased risk of missed antenatal diagnoses of fetal anomalies.

Low sensivitiy and higher false negative rate of detection of structural anomalies:
BMI <25: Sensitivity 32%, false-negative rate 68% BMI >30: Sensitivity 22%, false-negative rate 78%

Fetal Surveillance

BMI >35: More likely to have inaccurate SFH measurements and should be referred for serial growth scans

Serial measurements of SFH recommended at each antenatal appointment from 24 weeks

Induction of labour: 60% of obese primiparous women and 90% of obese multiparous women achieved vaginal birth

Labour and Delivery

Active management of 3rd stage in BMI >30: Reduces risk of PPH, postpartum anaemia, blood transfusion, prolonged 3rd stage, and use of therapeutic oxytocic drugs.

Booking BMI >35: Advise planned labour and delivery in obstetric unit
Booking BMI 30-35: Individualised assessment of place of birth

Discuss labour and delivery before 36 weeks: Include labour plan, pain management, management of prolonged pregnancy

Induction of labour:

  1. Elective IOL may reduce the risk of Caesarean delivery without increasing risk of adverse outcomes.
  2. Consider where macrosomia is suspected as IOL results in lower birth weight, reduced risk of fetal fractures and shoulder dystocia, and no change in risk of Caesarean section irrespective of maternal BMI.

Women with booking BMI =/>30 should have individualised decision for VBAC. Class III obesity is associated with increased risk of uterine rupture and neonatal injury.

Advise venous access early in labour for BMI =/>40

Surgical Techniques

Surgical access challenging due to presence of panniculus

Vertical suprapannus vs transverse infrapannus skin incisions: Increased operative morbidity including bleeding, classical hysterotomy, prolonged post-operative hypoxaemia, and respiratory compromise.

Prophylactic antibiotics for BMI =/>30: Reduces incidence of wound infection, endometritis, serious infectious complications

Women with >2cm subcutaneous fat should have suturing of the subcutaneous tissue space to reduce the risk of wound infection and separation

Postpartum Care

Breastfeeding: Women with booking BMI =/> 30 should receive appropriate specialist advice and support. Onset of breastfeeding is likely more complicated. Extra help is needed to ensure frequent and effective milk removal to stimulate lactogenesis and assistance with physical difficulties attaching the neonate to large breasts.

Women diagnosed with GDM have increased risk of developing T2DM, especially within the first 5 years

Contraception: According to FSRH guidelines. Note increased risk of VTE with hormonal contraceptive pill.

Pregnancy Following Bariatric Surgery

Minimum waiting period of 12-18 months recommended to allow stabilisation of body weight and allow correct identification and treatment of any nutritional deficiencies

Support women to lose weight and offer referral to weight management services

Decreased risk: Gestational diabetes, hypertensive disorders in pregnancy, macrosomia, and congenital defects

Increased risk: Small for gestational age babies, preterm delivery, NICU admission, maternal anaemia, and maternal nutritional deficiencies

Overall better obstetric outcome after bariatric surgery compared with women with class III obesity managed conservatively

High-risk pregnancies that should have consultant led care

Advise nutritional surveillance and screening for deficiencies during pregnancy:

  1. Pregnancy can exacerbate nutritional deficiencies predating pregnancy
  2. Women with malabsorptive procedures involving anatomical changes to the GI tract are at high risk of anaemia, micronutritional deficiencies (Vitamin B12, iron, folate, Vitamin ADEK) and macronutritional deficiencies (fat and protein).

Refer to a dietician for advice regarding nutritional needs (vitamin and mineral supplementation)

Women with gastric band insertion: Consider deflation for duration of pregnancy depending on circumstances. Hyperemesis may be pathological and related to gastric band slip or internal hernia.
Women with gastric band or sleeve gastrectomy: Increased risk of reflux and aspiration.