Obesity in Pregnancy

Overview

Obesity in pregnancy is defined as a pre-pregnancy body mass index (BMI) of ≥30 kg/m², though in South Asian contexts like Sri Lanka, lower thresholds (e.g., Asian cutoffs: obesity ≥25 kg/m²) are sometimes used in research due to higher risks at lower BMIs. It is a growing concern globally and in Sri Lanka, where the prevalence of overweight and obesity among pregnant women in the first trimester has risen from 15.2% in 2011 to 31.3% in 2020, according to national health data. A 2019 study in Anuradhapura district reported 15.3% overweight (BMI 23-24.9 kg/m²), 31.4% obesity grade I (25-29.9 kg/m²), 1.5% grade II (30-34.9 kg/m²), and 2% grade III (≥35 kg/m²) using Asian cutoffs, with underweight at 15.9%. Obesity increases risks for maternal complications like gestational diabetes mellitus (GDM), hypertensive disorders, thromboembolism, and cesarean delivery, as well as fetal issues such as macrosomia, congenital anomalies, and low birth weight (LBW). In Sri Lanka, national guidelines emphasize screening, monitoring, and lifestyle interventions, aligning with the Institute of Medicine (IOM) 2009 gestational weight gain (GWG) recommendations and WHO BMI classifications. Key resources include the Maternal Care Package: A Guide to Field Healthcare Workers (Family Health Bureau, Ministry of Health, Sri Lanka) available here and the Basic Maternal Care Manual (2023) from Family Health Bureau. General obesity management guidelines exclude pregnant women but note contraindications during pregnancy.

Classification

Sri Lankan national maternal care guidelines use WHO international BMI cutoffs for pregnancy:

• Underweight: <18.5 kg/m²
• Normal: 18.5-24.9 kg/m²
• Overweight: 25-29.9 kg/m²
• Obese: ≥30 kg/m²

However, studies often apply Asian-specific cutoffs (overweight ≥23 kg/m², obesity ≥25 kg/m²) to account for ethnic predispositions to metabolic complications. BMI calculation is mandatory at the first antenatal visit.

Signs and Symptoms

Many obese pregnant women are asymptomatic, but common issues include fatigue, shortness of breath, back pain, and sleep apnea. Complications may present as hypertension (elevated blood pressure), hyperglycemia, or excessive fetal growth detected via ultrasound or symphysio-fundal height (SFH) measurements. In Sri Lanka, routine screening identifies risks early.

Causes and Pathophysiology

Obesity stems from genetic, lifestyle, and environmental factors, exacerbated by high-calorie diets and sedentary behavior. In pregnancy, it leads to insulin resistance, inflammation, and placental dysfunction, increasing risks of GDM and preeclampsia. In Sri Lanka, socioeconomic factors like urban living and higher income correlate with central obesity (waist circumference >80 cm in 35% of pregnant women).

Risk Factors

• Pre-pregnancy BMI ≥25 kg/m², advanced maternal age, multiparity, family history of diabetes or obesity.
• In Sri Lanka: Ethnic groups like Moors, urban/rural disparities, low education, and diets high in refined carbs.
• Previous macrosomic baby (>3.5 kg) or GDM.

Diagnosis

• Calculate BMI at first antenatal visit using weight and height.
• Screen for complications: If BMI ≥25 kg/m², perform postprandial blood sugar (PPBS); if >120 mg/dL, refer for oral glucose tolerance test (OGTT).
• Monitor blood pressure, urine protein, and fetal growth via SFH.

Treatment

Management is supportive, focusing on lifestyle rather than weight loss:

• Antenatal: Counsel on healthy eating (balanced diet, portion control) and physical activity (e.g., walking). For BMI ≥25 kg/m², monitor for hypertension, GDM, and macrosomia. Refer to specialist if BMI ≥30 kg/m².
• GWG Recommendations (IOM 2009): Underweight 12.5-18 kg; Normal 11.5-16 kg; Overweight 7-11.5 kg; Obese 5-9 kg. Monitor weight gain and SFH.
• Intrapartum: Higher risk of cesarean; prepare for complications like shoulder dystocia.
• Postpartum: Encourage breastfeeding, contraception advice (avoid injectables if BMI >30 kg/m²), and lifestyle changes to prevent future obesity.
• No pharmacotherapy or bariatric surgery during pregnancy; all anti-obesity meds contraindicated.

Prevention

Pre-conception: Achieve healthy BMI through diet and exercise. In pregnancy: Adhere to GWG guidelines, promote nutrient-dense foods amid economic challenges. Sri Lanka's antenatal clinics provide free counseling and monitoring.

Prognosis

With management, outcomes improve, but obesity raises odds of GDM (higher in obese women), preeclampsia, and LBW if GWG is inadequate in underweight but not always in obese. Long-term: Increased maternal risk of type 2 diabetes and cardiovascular disease; offspring risk of obesity.

Epidemiology

In Sri Lanka, obesity in pregnancy varies regionally (23-46%), higher in urban areas and among certain ethnic groups. It contributes to the double burden of malnutrition (underweight and obesity coexistence). National efforts focus on universal antenatal care to address this.

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