Oxford Handbook of Midwifery by Janet Medforth, Sue Battersby, Maggie Evans, Beverley Marsh, Angela Walker
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Kingdom. Dietary reference values for the United Kingdom . London: HMSO.
CHAPTER 5 Health advice in pregnancy
86
Weight gain in pregnancy and body mass index
Weight gain during pregnancy is extremely variable and can be influenced by factors such as maternal age, parity, BMR, diet, smoking, pre-pregnancy weight, size of the fetus, and maternal illness such as diabetes. The weight gain is distributed between the fetus, placenta, membranes, amniotic fluid, and the physiological development of maternal organs, e.g. uterus and breasts (blood and fat deposition in preparation for lactation). Most healthy women in the UK gain between 11 and 16kg, although young mothers and primigravidae usually gain more than older mothers and multigravidae. 1
An optimal weight gain of 12.5kg is the figure used for an average pregnancy. This is associated with the lowest risk of complications during pregnancy and labour and of low birthweight babies. 2 Maternal weight gain tends to be more rapid from 20 weeks onwards, although excessive weight gain during pregnancy is associated with postpartum weight retention, as is increased weight gain in early pregnancy compared with late pregnancy. Weight gains above 12.5kg in women of normal pre-
pregnancy BMI are unlikely to reflect an increase in fetal weight, maternal lean tissue, or water.
Perinatal outcome has a complex relationship with maternal pre- pregnancy BMI, as well as with antenatal weight gain. Calculating the BMI is a method of estimating the amount of body fat, based on weight and height. The index is calculated by dividing the individual’s weight in kilograms by the square of his or her height in metres. Many charts are available for instant grading (Table 5.1).
Table 5.1 Grading of weight by BMI
BMI Interpretation
<20 Underweight
20–24.9 Desirable
25–29.9 Overweight
>30 Obese
Appropriate weight gain for individual women should be based on their pre-pregnancy BMI (Table 5.2), as lower perinatal mortality rates are associated with underweight women who achieve high weight gains and overweight women who achieve low gains. The number of women in the obese category of BMI is escalating and rapidly becoming a major public health problem within maternity care. 3 Maternal and perinatal complica- tions are much more prevalent, such as an increased risk of gestational diabetes, pre-eclampsia, macrosomia, and perinatal mortality. 3,4
WEIGHT GAIN IN PREGNANCY AND BODY MASS INDEX
87
Table 5.2 Weight gain in pregnancy and BMI
Pre-pregnancy body mass index [weight (kg)/height (m 2 )]
Recommended weight gain kg lb
Low (<19.8) 12.5–18.0 28–40
Normal (19.8–26) 11.5–16.0 25–35
High (26.0–29.0) 7–11.5 15–25
Obese (>29) 1 6 (min.) 14 (max.)
Recommended reading
Webster-Gandy J, Madden A, Holdsworth M (2006). Oxford Handbook of Nutrition and Dietetics . Oxford: Oxford University Press.
Hytten FE (1991). Weight gain in pregnancy. In Hytten FE and Chamberlain G (eds) Clinical Pathology in Obstetrics . London, Blackwell Scientific: 173–203.
Goldberg GR (2000). Nutrition in pregnancy. Advisa Medica , London, 1 (2): 1–3.
Veerareddy S, Khalil A, O’Brien P (2009). Obesity implications for labour and the puerperium.
British Journal of Midwifery, 17 (6): 360–362.
Stewart FM, Ramsay JE, Greer IA (2009). Obesity: impact on obstetric practice and outcome.
Obstetrician and Gynaecologist , 11 (1): 25–31.
CHAPTER 5 Health advice in pregnancy
88
Food safety
Listeriosis
Listeria monocytogenes is a Gram-positive bacterium that is normally found in soil and water, on plants, and in sewage. The incidence of listeriosis in adults is 0.5:100 000 and the mortality rate is about 26% in vulnerable groups such as babies, the elderly, immunocompromised individuals (such as those with acquired immune deficiency syndrome (AIDS)), and during pregnancy. Infection is usually asymptomatic in healthy adults.
Currently it is thought to affect approximately 1 in 20 000 pregnancies and, due to the
CHAPTER 5 Health advice in pregnancy
86
Weight gain in pregnancy and body mass index
Weight gain during pregnancy is extremely variable and can be influenced by factors such as maternal age, parity, BMR, diet, smoking, pre-pregnancy weight, size of the fetus, and maternal illness such as diabetes. The weight gain is distributed between the fetus, placenta, membranes, amniotic fluid, and the physiological development of maternal organs, e.g. uterus and breasts (blood and fat deposition in preparation for lactation). Most healthy women in the UK gain between 11 and 16kg, although young mothers and primigravidae usually gain more than older mothers and multigravidae. 1
An optimal weight gain of 12.5kg is the figure used for an average pregnancy. This is associated with the lowest risk of complications during pregnancy and labour and of low birthweight babies. 2 Maternal weight gain tends to be more rapid from 20 weeks onwards, although excessive weight gain during pregnancy is associated with postpartum weight retention, as is increased weight gain in early pregnancy compared with late pregnancy. Weight gains above 12.5kg in women of normal pre-
pregnancy BMI are unlikely to reflect an increase in fetal weight, maternal lean tissue, or water.
Perinatal outcome has a complex relationship with maternal pre- pregnancy BMI, as well as with antenatal weight gain. Calculating the BMI is a method of estimating the amount of body fat, based on weight and height. The index is calculated by dividing the individual’s weight in kilograms by the square of his or her height in metres. Many charts are available for instant grading (Table 5.1).
Table 5.1 Grading of weight by BMI
BMI Interpretation
<20 Underweight
20–24.9 Desirable
25–29.9 Overweight
>30 Obese
Appropriate weight gain for individual women should be based on their pre-pregnancy BMI (Table 5.2), as lower perinatal mortality rates are associated with underweight women who achieve high weight gains and overweight women who achieve low gains. The number of women in the obese category of BMI is escalating and rapidly becoming a major public health problem within maternity care. 3 Maternal and perinatal complica- tions are much more prevalent, such as an increased risk of gestational diabetes, pre-eclampsia, macrosomia, and perinatal mortality. 3,4
WEIGHT GAIN IN PREGNANCY AND BODY MASS INDEX
87
Table 5.2 Weight gain in pregnancy and BMI
Pre-pregnancy body mass index [weight (kg)/height (m 2 )]
Recommended weight gain kg lb
Low (<19.8) 12.5–18.0 28–40
Normal (19.8–26) 11.5–16.0 25–35
High (26.0–29.0) 7–11.5 15–25
Obese (>29) 1 6 (min.) 14 (max.)
Recommended reading
Webster-Gandy J, Madden A, Holdsworth M (2006). Oxford Handbook of Nutrition and Dietetics . Oxford: Oxford University Press.
Hytten FE (1991). Weight gain in pregnancy. In Hytten FE and Chamberlain G (eds) Clinical Pathology in Obstetrics . London, Blackwell Scientific: 173–203.
Goldberg GR (2000). Nutrition in pregnancy. Advisa Medica , London, 1 (2): 1–3.
Veerareddy S, Khalil A, O’Brien P (2009). Obesity implications for labour and the puerperium.
British Journal of Midwifery, 17 (6): 360–362.
Stewart FM, Ramsay JE, Greer IA (2009). Obesity: impact on obstetric practice and outcome.
Obstetrician and Gynaecologist , 11 (1): 25–31.
CHAPTER 5 Health advice in pregnancy
88
Food safety
Listeriosis
Listeria monocytogenes is a Gram-positive bacterium that is normally found in soil and water, on plants, and in sewage. The incidence of listeriosis in adults is 0.5:100 000 and the mortality rate is about 26% in vulnerable groups such as babies, the elderly, immunocompromised individuals (such as those with acquired immune deficiency syndrome (AIDS)), and during pregnancy. Infection is usually asymptomatic in healthy adults.
Currently it is thought to affect approximately 1 in 20 000 pregnancies and, due to the
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