obesity in pregnancy

Question 1

What is the risk of HTN in pregnancy if BMI <18

Over 40

Answer 1

BMI <18 GHTN 1%

BMI >40 risk 10%

Question 2

Risk of
spont vaginal birth
LSCS
instrumental

With normal BMI vs BMI 40

Answer 2

Normal BMI // BMI 40 
spont vaginal birth 
55% // 44%
LSCS 
33%// 52%
instrumental
13% // 5%

Question 3

Risk perinatal death per BMI

Answer 3

<18 0.5%
25-30 1% 
30-35
35-40 1.5% 
40+ 2%

Question 4

macrosomia risk per BMI

Answer 4

BMI 25 11%

BMI over 40 20% risk

Question 5

Antenatal risks of obesity

maternal and fetal

Answer 5

maternal 
maternal death 
GDM
PET 
OSA
UTI
anxiety and depression

fetal 
miscarriage 
Congenital abnormalities eg NTD 
PTB - mostly due to co morbidity 
macrosomia 
stillbirth OR 1.4

Question 6

Preconception risk obesity

Answer 6

infertility - poor quality egg and embryo

Question 7

Intrapartum risk

Answer 7

Maternal
BMI over 35 50% less likely to have gone into spont labour by 42 weeks
IOL OR 1.7
LSCS OR 1.8
(BMI over 40 OR 2.5) 
FTP
Difficulty for FHR monitoring 
PPH 1.4 

Anaesthetic risk
High epidural failure, increase GA, difficulty with airway

fetal 
Shoulder dystocia
Macrosomia 
This increases the risk of low apgars, lower umbilical pH, increased risk fetal injuries, overall morbidity increased by 8% 
Increased NICU admissions,

Question 8

VBAC and obesity

what are the risks and how to counsel

Answer 8

Individualise counselling
Doubles rupture rate from 1% to 2%

Higher failure rate - about 40% EMLSCS - lean controls 15% EMLSCS rate
5 X increased risk of neonatal injury 1.1% compared to lean controls (0.2%)
overall neonatal morbidity 7% - up to 14% if morbid obesity (lean controls 4% )

Question 9

postnatal risks of obesity

Answer 9

PPH OR 1.4
VTE 
wound infection
Reduce breastfeeding, low initiation and maintenance 
Increased hospital stay
Post natal depression 

neonatal
obesity
NICU admission

Question 10

Risks of previous bariatric surgery on pregnancy

Answer 10

Increased risk SGA PTB and maternal anaemia

Reduces risk of macrosomia GDM and HTN

Question 11

what is the risk of inter pregnancy weight gain - how does it alter the risk of the next pregnancy

Answer 11

Increase in 3 or more units of BMI increases risk of LSCS by 32% compared to weight neutral

Increased risk for LGA by 87%

interpregnancy weight loss improves
HTN, GDM, fetal macrosomia, VBAC success, reduces the risk of still birth,

4.5 kg of weight loss between the 1 and 2 pregnancy reduces the risk of developing GDM by 40%

Question 12

How to manage obesity - pre pregnancy

Answer 12

Weight and lifestyle advice
diet modification and exercise
Recommend for all woman with BMI voer 30 they should loose weight before pregnancy

Discuss the risks of obesity and pregnancy

Monitor and document BMI

5 mg folic acid and iodine

Weight loss medications are not recommended periconception

Question 13

What is the advice for pregnancy after bariatric surgery

Answer 13

Long term vitamin supplementation

Refer to dietician for additional supplementation
Avoid pregnancy 12-24 months

Question 14

Fetal anomaly screening in woman with high BMI - how does it change?

Answer 14

USS for NT is more challenging
may require TV

If NT cannot be seen then offer 2nd trimester screen

NIPT is less reliable as lower free cell DNA

amnio is more challenging technically

Question 15

Antenatal care for obese woman

Answer 15

Document BMI
Weight gain targets
MDT approach
Medications and surgery during pregnancy not recommended
Take care to offer psychological support and make referrals if mental health problems

Serial growth scans
T3 (BMI over 35)

Early GTT with repeat at 28 weeks if first normal
PET surveillence
Consider aspirin

Influenza vaccine
Anaesthetic consult

Question 16

What is recommended weight gain for different booking BMI

how much for twins?

Answer 16

<18.5 12.5-18kgs
up to 24.9 11.5-16 kgs
25-30 6.8 - 11 kgs
30+ 5-9kgs

Twins
o Normal weight women should gain 17-25 kg at term,

o Overweight women should gain 14-23 kg at term, and

o Obese women should gain 11-19 kg at term.

Question 17

Intrapartum management

Answer 17

NICE recommends BMI over 35 delivers in a obstetric unit
No consensus of timing on delivery for BMI alone
(IOL 40/40 reduces LSCS risk) - BMI over 35 4X higher SB risk !
Anaesthetic aware (if BMI over 40)
(consider early epidural, long needles, USS guidance for insertion)
If weight over 120 theatre aware (ensure equipment available)
IV access is BMI over 40
confirm presentation - by USS if unsure
Ensure Snr obs aware / attend operative births
Obesity alone not an indication for CEFM
(RCOG)
Can have difficulty with Monitoring
Active management of third stage

LSCS - subcut fat sutures
IVAB
No evidence for negative pressure dressings

Question 18

Post natal management obesity

Answer 18

VTE prophylaxis 
Additional breastfeeding support 
nutritional advice to minimise weight rention
if GDM then 6 week HbA1c 
Contraception - OCP increases VTE risk

Question 19

What are the BMI classes of obesity?

Answer 19

normal 18.5-24.99
overweight 25-29.99
Class 1 30-35
Class 235-40
Class 3 40+