Case 56: Obesity in pregnancy

 

Case 56: Obesity in pregnancy

CASE 56: OBESITY IN PREGNANCY

History

A woman has been referred for a hospital antenatal appointment at 16 weeks’ gestation. This

is her first pregnancy. She is 38 years old.

She booked for antenatal care with the midwife at 7 weeks and the only significant risk factor

identified was that her body mass index was 36 kg/m2. She has always been overweight and

considers her weight as normal for her. There is no significant past medical or gynaecological history.

Examination

Weight is 95 kg. Blood pressure is 145/88 mmHg. The uterus is not palpable on abdominal

palpation but hand-held Doppler ultrasound reveals a fetal heartbeat of 155/min.

INVESTIGATIONS

Urinalysis: negative

Booking bloods:

Syphilis: negative

HIV: negative

Hepatitis B: negative

Rubella: immune

Random blood glucose: 4.7 mmol/L

Blood group A: positive

Haemoglobin 13.1 g/dL

Questions

• How will you advise this woman about the possible effects of obesity on her pregnancy?

• What specific management plans should be put in place for her in view of her body

mass index?100 Cases in Obstetrics and Gynaecology

152

ANSWER 56

Obesity in pregnancy is defined as body mass index (BMI) of greater than 30 kg/m2 at first

antenatal appointment and occurs in up to 20 per cent of women. Twenty-seven per cent of

maternal deaths occur in obese women, and most adverse maternal and fetal outcomes are

overrepresented in obese women.

Advice on effects of obesity on pregnancy

Obese women should be sensitively advised of the increased risk of the following disorders

in pregnancy: gestational diabetes (two- to threefold), hypertensive disorders (two- to threefold), venous thromboembolism (ninefold), slow labour and caesarean section (twofold),

postpartum haemorrhage (twofold) and wound infection (twofold).

Fetal risks of maternal obesity include increased congenital abnormality (60 per cent

increased risk), prematurity (20 per cent increased risk), macrosomia (two- to threefold),

shoulder dystocia (threefold), stillbirth (twofold) and neonatal death (twofold).

Specific pregnancy management for this woman

Preconception advice

Ideally this woman should have had preconceptual information and advice regarding the

pregnancy risks, with weight loss support offered prior to conception. She should have been

prescribed folic acid at the higher dose of 5 mg daily due to the higher incidence of neural

tube defects in babies of obese mothers. Similarly as an obese woman she is more likely to

be vitamin D deficient and should have vitamin D supplementation during pregnancy and

breast-feeding.

Management in pregnancy

• Anaesthetic consultation should be arranged to discuss the possible increased difficulty with venous access, regional anaesthesia or general anaesthetic.

• Antenatal thromboprophylaxis should be considered if there are two or more other

risk factors such as smoking, immobility or parity greater than 3. The dose of lowmolecular-weight heparin is calculated according to the woman’s weight.

• Increased frequency of antenatal blood pressure measurements should be arranged

and a large cuff is necessary for accurate assessment.

• Gestational diabetes screen (glucose tolerance test) should be performed by 28 weeks.

• With regard to planning for delivery, this woman should be advised to have a hospital birth (not home birth) due to increased maternal and fetal risks.

• Although a caesarean is more likely than in a non-obese woman, in view of the increased

risks associated with operative delivery, a vaginal birth should be encouraged.

• Early intravenous access should be established in labour and there should be active

management of the third stage, due to postpartum haemorrhage risk.

• Throughout the pregnancy and postnatally she should be encouraged to lose weight

through moderate exercise and dietary control