Obesity in Pregnancy
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Direct answer
Obesity in pregnancy is defined by a body mass index of 30 kg/m2 or more at booking (overweight is 25-29.9), and it converts an otherwise low-risk pregnancy into a high-risk one: gestational diabetes, hypertensive disorders including pre-eclampsia, miscarriage, thromboembolism, obstructive sleep apnoea, failed induction, caesarean section, wound infection and postpartum haemorrhage all rise with the body mass index, while the fetus faces macrosomia, congenital anomaly (neural tube defects partly linked to lower folate bioavailability), stillbirth and childhood obesity. Management is anticipatory: weight-gain targets (5-9 kg for body mass index 30 or more), glucose screening with an oral glucose tolerance test, aspirin 150 mg nightly from 12 weeks in women with additional risk factors, thromboprophylaxis during admission, and anaesthetic review well before labour.
What you must remember
- Class definitions: overweight 25-29.9, obesity class I 30-34.9, class II 35-39.9, class III 40 and above; Asian Indians develop metabolic complications at lower body mass index, and the Government of India uses overweight cut-offs of 23 kg/m2 for public-health action.
- First trimester: tall and accurate weight at booking, oral glucose tolerance test earlier than 24-28 weeks if body mass index is 30 or more with additional risk factors; folic acid 400-500 micrograms daily (5 mg if diabetes or previous neural tube defect).
- Pre-eclampsia prophylaxis: aspirin 150 mg at night from 12 weeks until 36 weeks when one high-risk factor (including obesity with another qualifier) or multiple moderate factors is present; calcium 1-2 g daily where intake is low.
- Gestational weight gain: institute of Medicine targets — total 5-9 kg for body mass index 30 or more; "eating for two" is replaced by a dietician-structured plan and 30 minutes of daily moderate activity.
- Thromboprophylaxis: obesity multiplies venous thromboembolism risk; prophylactic enoxaparin 40 mg daily during any hospital admission and for 7-10 days postpartum in high body mass index after caesarean, dosed upward (0.6 mg/kg in very high weights per protocol).
- Anaesthetic planning: early cannulation, assessment for difficult airway and difficult neuraxial block in class II-III obesity; an epidural attempt in early labour is advised before anatomy distorts.
- Intrapartum realities: higher failed induction and post-dates rates, shoulder dystocia risk with macrosomia, limited monitoring reliability, and a higher caesarean threshold for fetal distress signals — plus a theatre table weight limit and correctly sized cuffs and instruments.
Walking a booking visit
A 27-year-old primigravida weighs 96 kg at 158 cm — body mass index 38, class II. Booking: blood pressure with a large cuff, oral glucose tolerance test moved earlier (16-20 weeks) because obesity plus a strong family history of diabetes justifies it, aspirin 150 mg nightly and calcium from 12 weeks for pre-eclampsia prophylaxis, folic acid already started, baseline liver function. Weight-gain target discussed frankly — 5-9 kg total, not the 11-16 kg her relatives will prescribe culturally. The 20-week anomaly scan is harder through adipose tissue, so a focused cardiac view is arranged where available.
Third trimester: growth scans every 4 weeks because palpation underestimates fetal weight; sleep apnoea screening if she snores with daytime sleepiness; anaesthesia clinic at 34 weeks; a labour plan — continuous monitoring, epidural offered early, shoulder dystocia drill rehearsed. She delivers vaginally at 39 weeks, the third stage actively managed with oxytocin 10 units because uterine overdistension and obesity both predispose to atonic haemorrhage. Postpartum: enoxaparin 40 mg daily for ten days, breastfeeding support (obesity delays lactogenesis), and an inter-pregnancy weight-loss plan.
How the exam frames it
Screening questions mine the associations and numbers: the neural tube defect link (folic acid 5 mg in high-risk obesity), aspirin 150 mg nightly from 12 weeks, the Institute of Medicine gain of 5-9 kg, and the miscarriage, pre-eclampsia, gestational diabetes, stillbirth and postpartum haemorrhage list. A favourite distractor asks the single best intrapartum preparation for class III obesity - early epidural or anaesthetic review, not elective caesarean. The Asian cut-off (23 kg/m2 for overweight in Indian guidelines) separates a generic answer from a nationally anchored one.
Frequently asked questions
What body mass index defines obesity in pregnancy?
A booking body mass index of 30 kg/m2 or more, with classes I to III grading severity; Indian public-health guidance flags 23 kg/m2 as overweight for Asian populations.
How much weight should a woman with obesity gain in pregnancy?
About 5-9 kg in total for a booking body mass index of 30 or more, achieved through a structured diet and daily moderate activity rather than unrestricted intake.
Which prophylactic medications suit obese pregnant women?
Aspirin 150 mg nightly from 12 to 36 weeks for pre-eclampsia risk, calcium 1-2 g daily where intake is low, folic acid 5 mg if additional neural tube defect risk exists, and enoxaparin 40 mg daily during admission.
Why does obesity raise caesarean and failed induction rates?
Mechanical and myometrial factors — taller uterine overdistension, higher rates of post-dates,macrosomia, and dysfunctional labour patterns — combine with monitoring difficulty to increase both primary caesarean and failed induction.
What fetal risks accompany maternal obesity?
Neural tube and other congenital anomalies, macrosomia with shoulder dystocia and neonatal hypoglycaemia, preterm birth, stillbirth, and increased childhood obesity and metabolic risk.