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
- Miscarriage
- Caesarean delivery (risk increases 50% in overweight, and more than doubles in obese)
- Initiation and maintenance of breastfeeding; physiological delay in lactogenesis
- Pre-eclampsia and hypertensive disease in pregnancy
- Gestational diabetes (3-fold)
- Anaesthetic complications
- Postpartum haemorrhage
- Wound infections
- Maternal mortality
- Difficulty in assessment of fetal size, presentation, and external fetal monitoring
- Vitamin D deficiency
- Poor ultrasound visualisation of baby and difficulties in fetal surveillance and screening for anomalies
- Development of pressure sores due to immobility
- Venous thromboembolism
- Mental health problems: Depression, anxiety, eating disorders, serious mental illness
- Prolonged pregnancy
- 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
- Reduces risk of stillbirth
- Reduce risk of hypertensive complications
- Reduces risk of fetal macrosomia
- 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
- Congenital anomalies: Neural tube defects, spina bifida, cardiovascular anomalies, congenital cardiac defects, septal anomalies, cleft lip and palate, anorectal atresia, hydrocephaly, limb reduction
- Stillbirth
- Prematurity
- Macrosomia
- Neonatal death
- Neonatal admission: Up to 1.5 times more likely
- 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
- Risk for anaesthesia-related maternal mortality
- 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:
- Orlistat: Lipase inhibitor that inhibits absorption of dietary fats.
- Phentermine/topiramate: Promotes appetite reduction/suppression, and decreases food consumption (increased satiety). Use is linked to oral clefts, transmitted in breast milk.
- 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:
- BMI =/>35 (increased risk of pre-eclampsia)
- First pregnancy
- Maternal age >40 years
- Family history pre-eclampsia
- Multiple pregnancy
Higher risk of depression in obese women:
- Pregnancy: Obese 33%, overweight 28.6%, normal 22.6%
- 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:
- Elective IOL may reduce the risk of Caesarean delivery without increasing risk of adverse outcomes.
- 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:
- Pregnancy can exacerbate nutritional deficiencies predating pregnancy
- 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.