Chapter one

INTRODUCTION

1.1      Introduction

Obesity has been identified as a major risk factor for poor pregnancy out come. (Galtier et al., 2000; CMACE/RCOG 2010). It is most commonly defined as Body Mass Index (BMI) of greater than 30kilograms per square of height in meters (Galtier et al., 2000; CMACE/RCOG 2010). This definition is the same in both pregnant and non pregnant population (CMACE/RCOG 2010). For the pregnant woman, weight and height of the woman at first booking are obtained and the BMI calculated (CMACE/RCOG 2010). There are three different classes of obesity: BMI 30.0–34.9 (Class I); BMI 35.0–39.9 (Class 2); and BMI 40 and over (Class 3 or morbid obesity),(NICE 2006;WHO 2000). It is recognised that there is a continuous relationship between BMI and maternal morbidity and mortality (WHO2000).

Calculation of the body mass index requires the use of standard weighing scales and stadiometers and mathematical calculations by well trained personnel. These requirements may be lacking especially in developing societies such as ours.

The prevalence of obesity in pregnancy has continued to increase as its prevalence in the general public continues to rise. It has become necessary that adequate and non sophisticated methods of discovering obesity in pregnancy be

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identified in order to institute adequate management that will forestall poor outcome of the pregnancy.

1.2          Rationale for the study

The use of body mass index in identifying obesity in pregnancy may not be a sensitive and specific criterion. This is because in pregnancy, there is an additional weight gain due to the presence of the foetus and placenta (Campbell and Lees 2000; Ganong 2005). There is also an increase in size of maternal organs such as the breast and the uterus (Campbell and Lees 2000). There may also be accumulation of fluid in the extra cellular spaces in pregnancy which would increase the weight of the woman (Campbell and Lees 2000). Moreover the lordosis which occurs in pregnancy is normally associated with a decrease in height of the woman (Scholl et al., 1990; Hirabaya et al., 1997). There may even be an increase in height of adolescent mothers in pregnancy even though this may be very small. (Scholl et al., 1990) Appropriate management of women with maternal obesity can only be possible with consistent identification of those women who are at risk (CMACE/RCOG 2010). The NICE Antenatal Care guideline (2008) recommends that maternal height and weight should be recorded for all women at the initial booking visit (ideally by 10 weeks gestation) to allow the calculation of BMI. It is common knowledge that very few women book at 10 weeks; even in developed countries (Heslehurt et al., 2007).

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The measurement of the Mid Upper Arm , Hip, Waist and Calf Circumferences can be taken at very low cost requiring neither the expensive and sophisticated equipment nor mathematical calculations hence may prove to be invaluable in assessing pregnant women especially in developing societies.

These measurements can be taken while standing, sitting or lying making assessment of the sick woman who is unable to stand easy (Collins 1996). Therefore a study like this which would identify the normal range for these anthropometric indices - Mid Upper arm, Waist, Hip and Calf Circumference, is necessary in order to identity those who are well above the normal hence obese and at risk of obesity related conditions.

1.3 Aim and Objectives

1.3.1 AIM

To identify some anthropometric indices that can be used to identify obesity in pregnancy

1.3.2 Specific Objectives

i.            To measure some Anthropometric indices –Weight, Height, Mid Arm, Calf ,Waist and Hip circumferences in pregnant women at different trimesters.

ii.           To identify the relationship between Body Mass Index and the circumferences of the Mid Arm, Calf, waist and the Hip at different trimester.

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iii.     To identify the normal limit of these indices at different trimesters of