Abstract

 

Obesity in pregnancy is currently a major health problem worldwide according the WHO. Prevalence of obesity during pregnancy has doubled in the past 20 years, and obesity is strongly associated with poor gestational and perinatal outcomes. Pregnancy is characterized as a brief observation period in which the anthropometric index undergoes rapid changes. The measurements of weight and height and their associations, to produce pre-gestational Body mass index (BMI) and (less commonly) the calculation of arm circumferences and cutaneous folds have been recommended in the anthropometric nutritional assessment of the pregnant woman. This study determined other anthropometric parameters such as mid upper arm circumference, calf circumference, waist circumference and waist to hip ratio that can be  used to identify obesity in pregnancy. Data obtained by self- administered questionnaire, medical examination and anthropometric measurement of 578 pregnant women at different ages and trimesters was analysed using SPSS version 15. The result showed that 143 (25%) of the women were in the first trimester of pregnancy, 206(36%) were in second trimester while 229 (39%) were in the third trimester. The  women were between the ages of 15-40 years while the mean ages of the women in years were 28.86+5.26, 28.11+4.29 and 28.39+4.20 respectively in the first , second and third trimesters. There was no significant difference in the ages of the three groups (f= 1.44,p=0.32). The mean mid upper arm circumference (MUAC) and calf circumference(CC) in centimetre the first, second and third trimesters were 30.47±3.88, 30.23±4.02, 30.15±4.81and 36.81±3.50, 36.83±3.43 and 37.06±3.85  respectively with no significance difference (p=0.74,0.75). The mean waist circumferences were 92.31±10.78, 97.58±10.78 and 106.46±12.00 for the first, second and third trimesters respectively with a significant difference (p=0.001) The mean waist to hip ratios were 0.88±0.06,0.92±0.06 and 0.98±0.08  for the first, second and third trimesters respectively with significant 0.92±0.06 (p=0.001 ). All the parameters had positive correlation with BMI. Using the 75^th percentile of MUAC and CC (33cm and 39cm) in all trimesters , MUAC and CC were shown to have a sensitivity and specificity more than 70% when using the estimated pre-pregnancy weight as gold standards . Waist and waist to hip ratio increased as pregnancy increased hence there may be need for various cut off point as gestational age increased. These indices may be invaluable tools for identification of obesity in pregnancy.

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 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).

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

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

trimesters.

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

trimester.

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