Maternal obesity: pregnancy complications, gestational weight gain and nutrition

Authors


I Guelinckx, Kapucijnenvoer 35, bus 7001
3000 Leuven.
E-mail: isabelle.guelinckx@uz.kuleuven.ac.be

Summary

The obesity epidemic affects all, including women of reproductive age. One in five women attending prenatal care in the UK is obese. Prepregnancy obesity is associated with serious short- and long-term complications for mother and child. Furthermore, gestational weight gain (GWG) of obese pregnant women generally exceeds the Institute of Medicine recommended ranges. This observation can partially be explained by an unbalanced diet and lack of daily physical activity. Despite this, few lifestyle intervention trials in obese pregnant women are available. Two out of seven intervention trials focusing on GWG, nutrition and physical activity, reached a significant decrease in GWG. Developing guidelines to promote appropriated weight gain and healthy lifestyle in overweight and obese pregnant women remains a challenge.

This review aims to summarize the complications associated with maternal prepregnancy overweight and obesity and to discuss possible strategies to improve the lifestyle habits of pregnant women.

Introduction

The increasing prevalence of obesity worldwide has prompted the World Health Organization (WHO) to designate obesity as one of the most important global health threats (1). The epidemic is especially pronounced in young people, including women of reproductive age. Prepregnancy obesity is an independent risk factor for maternal and neonatal morbidity and mortality. The first aim of this review is to summarize the available knowledge on the complications related to excess prepregnancy body weight.

The origin of this epidemic is unhealthy lifestyle – high-energy and high-fat diet, physical inactivity and smoking. During periconceptual period and pregnancy, the composition of a woman's diet is of particular importance, as it may considerably influence the pregnancy, the delivery and the health of the mother and the infant later on. Next to the quality of the diet, a balanced energy intake is of interest as an excessive gestational weight gain (GWG) is not recommended. The Institute of Medicine (IOM) guidelines, published in 1990 and currently under review, suggest a GWG of 6.8–11.2 kg (15–25 lb) for overweight women and more than 6.8 kg (15 lb) for obese women (2,3). No upper limit is defined for obese women because of lack of data. The second aim of this review is to discuss the dietary habits of pregnant women and the impact of nutritional intervention studies on GWG, focusing on overweight and obese pregnant women.

Prevalence

It is common knowledge that overweight and obesity are increasing worldwide, in all populations and in all age categories. In the last years, obstetricians were more frequently confronted with overweight and obese pregnant women. Obesity among American pregnant women ranges from 18.5% to 38.3%, depending on the study-cohort and cut-off point used (4). This increasing trend is not only present in the USA. Figure 1 summarizes studies reporting the prevalence of prepregnancy overweight and obesity among pregnant women from different countries (5–29). The prevalence of obesity in pregnant women ranges from 1.8% to 25.3%, using WHO criteria [body mass index (BMI) > 30 kg m−2].

Figure 1.

Prevalence (%) of overweight and obesity in pregnant women. IOM, Institute of Medicine; WHO, World Health Organization.

Consequences of maternal prepregnancy obesity for the mother

The disadvantages of maternal obesity start even before conception. There is a higher prevalence of polycystic ovary syndrome (PCOS) among obese women. PCOS is an endocrine misbalance interfering with normal ovulation and menstruation, causing amenorrhea and endocrine infertility. In total, 30% up to 75% of women with PCOS are obese (30). Miscarriage takes place more often in overweight and obese women, both after natural conception and infertility treatment (7). The risk of miscarriage in obese women is 25–37% higher compared with lean women (31).

Most consistently described maternal complications during pregnancy and delivery of obese women are gestational diabetes, pregnancy-induced hypertension and pre-eclampsia, venous thrombo-embolism, labour induction and caesarean delivery. Tables 1 and 2 summarize the relative risk for these complications in respectively overweight women and obese women, compared with normal weight women (BMI 20–25 kg m−2).

Table 1.  Odds ratios (OR), adjusted odds ratios (AOR) or adjusted relevant risk (ARR) and 95% confidence interval of maternal complications, comparing overweight pregnant women and pregnant women with a BMI of 20–25 kg m−2
 HypertensionPre-eclampsiaGDMTEDLabour inductionCS
  • *

    Adjusted for age, race/ethnicity, education.

  • Adjusted for age, parity, educational status, smoking and ethnicity.

  • Adjusted for all statistically significant confounders such as maternal age and parity.

  • §

    Confounding variables not mentioned.

  • Adjusted for smoking, patients risk factors, multiple pregnancies and family risk factors.

  • **

    Adjusted for confounding variables identified from background data, obstetric risk factors and health behaviour.

  • ††

    Adjusted for age, skin colour, education, site, parity, weight gain, length of gestation.

  • §§

    Adjusted for maternal height, maternal education, weight gain, labour induction.

  • ¶¶

    Adjusted for several confounding factors, dependent on the complications.

  • BMI, body mass index; CS, caesarean section; GDM, gestational diabetes mellitus; TED, thrombo-embolic disease.

Rudra et al. (11)*  ARR 0.72   
  (0.23–2.40)   
Callaway et al. (25)  AOR 1.78  AOR 1.50
  (1.25–2.52)  (1.36–1.66)
Doherty et al. (23)AOR 2.60AOR 1.45AOR 2.71 AOR 1.36AOR 1.36
(1.49–4.55)(0.72–2.90)(1.32–5.55) (1.05–1.77)(1.04–1.86)
Graves et al. (20)    OR 1.6No separated data
    (1.1–2.4) 
Leeners et al. (78)AOR 1.9AOR 2    
(1.034–3.665)(1.36–2.983)    
Raatikainen et al. (13)**     AOR 1.22
     (1.10–1.35)
Rode et al. (12)OR 1.9OR 1.7OR 3.4   
(0.97–3.7)(1.2–2.4)(1.7–6.8)   
Seligman et al. (9)††     ARR 1.3
     (1.1–1.4)
Vahrantian et al. (79)§§     AOR 1.2
     (0.8–1.8)
Bo et al. (27)No data     
Jensen et al. (37) OR 1.4  OR 1.2OR 1.2
 (0.9–2.2)  (0.9–1.5)(0.9–1.6)
Nucci et al. (80)OR 2.46OR 1.26OR 1.98   
(1.99–3.04)(0.79–2.00)(1.56–2.53)   
Sebire et al. (10)¶¶ AOR 1.44AOR 1.68AOR 1.41  
 (1.28–1.62)(1.53–1.84)(0.91–2.19)  
Table 2.  Odds ratios (OR), adjusted odds ratios (AOR) or adjusted relevant risk (ARR) and 95% confidence interval of maternal complications, comparing obese pregnant women and pregnant women with a BMI of 20–25 kg m−2
 HypertensionPre-eclampsiaGDMTEDLabour inductionCS
  • *

    Adjusted for age, race/ethnicity, education.

  • Adjusted for age, parity, educational status, smoking and ethnicity.

  • Adjusted for all statistically significant confounders such as maternal age and parity.

  • §

    Confounding variables not mentioned.

  • Adjusted for smoking, patients risk factors, multiple pregnancies and family risk factors.

  • **

    Adjusted for confounding variables identified from background data, obstetric risk factors and health behaviour.

  • ††

    Adjusted for age, skin colour, education, site, parity, weight gain, length of gestation.

  • ‡‡

    Adjusted for maternal height, maternal education, weight gain, labour induction.

  • §§

    Adjusted for several confounding factors, dependent on the complications.

  • BMI, body mass index; CS, caesarean section; GDM, gestational diabetes mellitus; TED, thrombo-embolic disease.

Rudra et al. (11)*  ARR 3.25   
  (1.85–5.71)   
Callaway et al. (25)  AOR 2.95  AOR 2.02
  (2.05–4.25)  (1.79–2.28)
Doherty et al. (23)AOR 7.93AOR 3.74AOR 6.50 AOR 2.44AOR 2.2
(4.74–13.27)(1.95–7.17)(3.32–12.74) (1.72–3.45)(1.58–3.12)
Graves et al. (20)    OR 2.6OR 2.5
    (1.7–3.9)(1.6–3.9)
Leeners et al. (78)AOR 3.8AOR 3.2    
(1.668–9.099)(1.7–5.909)    
Raatikainen et al. (13)**     AOR 1.68
     (1.48–1.91)
Rode et al. (12)OR 4.8OR 2.7OR 15.3   
(2.3–9.9)(1.7–4.4)(8.2–28.6)   
Seligman et al. (9)††     ARR 1.8
     (1.5–2.0)
Vahrantian et al. (79)‡‡     AOR 1.5
     (1.05–2.0)
Bo et al. (27)OR 10.6     
(5.00–22.54)     
Jensen et al. (37) OR 3.8  OR 2.2OR 1.6
 (2.5–5.6)  (1.7–2.81)(1.3–2.1)
Nucci et al. (80)OR 6.60OR 3.92OR 2.36   
(5.06–8.60)(2.40–6.38)(1.65–3.39)   
Sebire et al. (10)§§ AOR 2.14AOR 3.6AOR 1.48  
 (1.85–2.47)(3.25–3.98)(0.82–2.69)  

Gestational diabetes increases the risk of fetal macrosomia (birth weight >4.5 kg at any gestational age) and the development of diabetes later on in life. Seventy per cent of the obese women with gestational diabetes develop type 2 diabetes within 15 years of delivery, compared with 30% of lean women (32).

Obesity is known to increase the risk of pregnancy-related hypertension and pre-eclampsia. Frederick et al. found that every unit increase in prepregnancy BMI resulted in an 8% increased risk of pre-eclampsia (33). Inversely, a significant decrease in risk is also noticed when BMI decreases (34).

Deep venous thrombosis and pulmonary embolism are the leading causes of maternal mortality in the UK (35). Both antepartum and post-partum, overweight and obese women are at higher risk of venous thromboembolism compared with normal weight women: adjusted OR 1.4 (95% CI 0.7, 2.8) for overweight women and 5.3 (95% CI 2.1, 13.5) for obese women (36).

In literature, there is disagreement about the risk for preterm delivery in obese women. Some studies suggest a decreased risk (10,24), others an increased risk (29) or even no difference compared with pregnant women with a normal BMI (4,37).

There is a linear trend between maternal prepregnancy BMI and risk for both elective and unplanned caesarean section (20,28). The risk is even higher when maternal obesity is combined with excessive GWG (9). Performing a caesarean delivery on obese women is technically more difficult as it results in an increased risk for anaesthetical complications (38) and operative complications such as excessive bleeding and post-partum infections (10). As a result of these complications, overweight and obese women are more frequently hospitalized, increasing the total cost of obstetrical care, the risk for hospital infections and the risk for deep venous thrombosis because of prolonged immobilization (4,10,25). Compared with planned caesarean delivery, vaginal birth after caesarean trials in obese women is three times likely to be complicated by infection and does not result in reduced costs (39).

After delivery, overweight and obese women more frequently suffer from haemorrhage, anaemia, genital and urinary tract infections, endometritis, stress incontinence and even depression (4,10,16,26). Maternal obesity also adversely affects breastfeeding initiation and duration (14).

For many pregnant women, post-partum weight retention is a concern. GWG is the strongest predictor for weight retention (40). Overweight and obese women tend to retain more weight because most of them gain weight above the IOM recommendations (3,40). However, no significant relation between prepregnancy weight and post-partum weight retention could be found (40,41).

Consequences of maternal prepregnancy obesity for the foetus

Maternal obesity is associated with a more than doubled risk of stillbirth and perinatal death (17).

A clear association exists between maternal obesity and fetal macrosomia (22,28). Macrosomia, together with maternal height and weight, gestational age and parity is suggested to be a good predictor for the risk of birth traumas such as shoulder dystocia and subsequently brachial plexus injury (42). On the long-term, children who are large-for-gestational-age (birth weight above 90th percentile) and exposed to an intrauterine environment of either maternal obesity or diabetes are at an increased risk of developing the metabolic syndrome and childhood obesity (43,44). These results are alarming as they show the presence of a viscous cycle over generations, as suggested by Catalano (45).

Recent studies have shown an association between maternal obesity and foetal birth defects like neural tube defects, abdominal wall defects, heart defects and multiple congenital anomaly syndromes (6). Obesity in combination with gestational diabetes acts synergistically on the pathogenesis of congenital anomalies (46). The risk of missing these congenital malformations is higher among obese pregnant women: because of the interposing fat layer, visualization of the foetus during the ultrasound examination is more complicated (47). For the same reason, foetal monitoring during labour is more difficult.

Because of previously mentioned infant complications (Tables 3 and 4), the percentage of babies admitted at the intensive care department is 3.5 times higher in case of maternal obesity (4).

Table 3.  Odds ratios (OR) or adjusted odds ratios (AOR) and 95% confidence interval of foetal complications, comparing infants of overweight women and infants of pregnant women with a BMI of 20–25 kg m−2
 Preterm deliveryStillbirthPerinatal deathMacrosomiaIntensive careHypo-glycaemiaJaundice
  • *

    Adjusted for age, parity, educational status, smoking and ethnicity.

  • Adjusted for confounding variables identified from background data, obstetric risk factors and health behaviour.

  • Adjusted for age, height, parity, smoking, years of schooling, working status, alcohol and caffeine intake, cohabitation with partner, gender of child.

  • §

    Adjusted for significant confouding variables including parity, race, and newborn gender.

  • Adjusted for several confounding factors, dependent on the complications.

  • BMI, body mass index.

Callaway et al. (25)*AOR 1.07AOR 1.16  AOR 0.92AOR 0.78AOR 1.02
(0.89–1.28)(0.62–0.17)  (0.73–1.16)(0.36–1.66)(0.92–1.12)
Oddy et al. (14)No data      
Raatikainen et al. (13)AOR 1.02AOR 1.54AOR 1.54 AOR 1.20  
(0.87–1.20)(0.88–2.68)(0.98–2.42) (1.06–1.37)  
Kristensen et al. (17) AOR 1.2AOR 1.0    
 (0.6–2.2)(0.4–2.2)    
Ehrenberg et al. (22)§   AOR 1.2   
   (1.1–1.4)   
Bo et al. (27)   No data   
Jensen et al. (37)OR 1.0 OR 1.8OR 1.2 OR 1.2OR 1.0
(0.6–1.9) (0.6–6.0)(1.0–1.6) (0.6–2.1)(0.6–1.8)
Nucci et al. (80)   OR 1.61   
   (1.30–2.00)   
Sebire et al. (10)AOR 0.82      
(0.78–0.86)      
Table 4.  Odds ratios (OR) or adjusted odds ratios (AOR) and 95% confidence interval of foetal complications, comparing infants of obese women and infants of pregnant women with a BMI of 20–25 kg m−2
 Preterm deliveryStillbirthPerinatal deathMacrosomiaIntensive careHypo-glycaemiaJaundice
  • *

    Adjusted for age, parity, educational status, smoking and ethnicity.

  • Adjusted for confounding variables identified from background data, obstetric risk factors and health behaviour.

  • Adjusted for age, height, parity, smoking, years of schooling, working status, alcohol and caffeine intake, cohabitation with partner, gender of child.

  • §

    Adjusted for significant confouding variables including parity, race, and newborn gender.

  • Adjusted for several confounding factors, dependent on the complications.

  • BMI, body mass index.

Callaway et al. (25)*AOR 0.95AOR 1.19  AOR 1.25AOR 2.57AOR 0.98
(0.76–1.19)(0.56–2.55)  (0.97–1.62)(1.39–4.78)(0.88–1.13)
Oddy et al. (14)AOR 2.08      
(1.39–3.12)      
Raatikainen et al. (13)AOR 1.12AOR 2.35AOR 2.19 AOR 1.38  
(0.92–1.36)(1.28–4.32)(1.33–3.62) (1.17–1.61)  
Kristensen et al. (17) AOR 3.1AOR 2.7    
 (1.6–5.9)(1.2–6.1)    
Ehrenberg et al. (22)§   AOR 1.6   
   (1.4–1.9)   
Bo et al. (27)   OR 4.48   
   (2.30–8.71)   
Jensen et al. (37)OR 1.6 OR 1.0OR 1.6 OR 0.9OR 1.0
(0.9–2.9) (0.2–1.3)(1.3–2.0) (0.5–1.8)(0.6–1.7)
Nucci et al. (80)   OR 1.53   
   (1.08–2.17)   
Sebire et al. (10)AOR 0.93      
(0.87–1.00)      

Nutrition and gestational weight gain

All previously mentioned complications are associated with prepregnancy overweight and obesity. If this prepregnancy obesity is combined with excessive GWG, there is an even higher risk for negative pregnancy outcome. The risk for a caesarean section more than doubled when obese women gain excessive weight compared with obese women with a normal GWG [Relative Risk (RR) 4th vs. 2nd weight gain quartile 2.2; 95% CI: 1.4–3.2] (9). It is crucial that overweight and obese women gain weight within the IOM recommendations (2).

Only a few studies interfered in GWG through lifestyle interventions, and even less studies focused on overweight or obese mothers. The first randomized controlled trial (RCT) by Borberg et al. advised a small group of obese women to restrict energy intake between 1800 and 2000 kcal with an intake of carbohydrates between 150 and 180 g day−1 (48). This group was compared with three control groups: underweight, normal and obese women. The results were striking: the GWG of the obese intervention group was halved (6.2 kg ± 2.1) compared with the other groups (underweight 12.9 kg ± 4.6; normal 11.9 kg ± 1.5; obese 13.6 ± 5.6) with a net weight loss after delivery. In the third trimester, the fasting insulin concentrations in the intervention group increased only 38% compared with the 140% of the obese women in the control group. Recently, Wolff et al. confirmed these results. The obese women in the intervention group restricted the GWG to 6.6 ± 5.5 kg vs. a gain of 13.3 ± 7.5 kg in the control group (P = 0.002; 95% CI 2.6–10.8 kg) (49).

Other intervention studies were less successful. Gray-Donald et al. compared dietary, weight and glycemic indicators among pregnant Cree women with a mean BMI of 29.6–30.8 kg m−2 (2,50). This randomized controlled intervention showed no change in dietary intake except for a higher folate and reduced caffeine intake in the intervention group. Also GWG [13.2 ± 8.3 kg for control subjects and 12.0 ± 6.4 kg (P = 0.29) for intervention subjects] and plasma glucose concentrations remained comparable. Self-reported physical activity levels remained very low in both groups.

Another prospective cohort study with a historical control group found a significant reduced risk of excessive GWG (OR = 0.41, 95% CI = 0.20–0.81) in women who were enrolled in an by US-mail education programme about a healthy diet and exercise during pregnancy (51). This intervention was only successful in the normal and overweight group with low income, but not in the high-income group. Polley et al. performed a clinical study with low-income women (52). In this RCT, 110 subjects were stratified by race and BMI category into intervention or control group. Within the intervention group, the frequency of excessive GWG was significantly reduced among normal-weight women compared with the control group (33% versus 58%, P < 0.05); however, this result could not be confirmed in the obese subgroup. Among overweight women, two-thirds exceeded the recommended GWG at some point in their pregnancy grouping both groups. The intervention had no effect on the average GWG, pregnancy complications and behaviour (dietary fat consumption and physical activity). Kinnunen et al. studied 132 non-obese primiparous women, divided in an intervention group and a control group (53). The lifestyle counselling helped pregnant women to increase vegetable, fruit and fibre intake, but was unable to prevent excessive GWG. Widga et al. found the same results in low-income women in a randomized design (nutritional counselling vs. control) (54). Although dietary behaviour significantly changed in the intervention group (total energy, folate, vit B6, iron, zinc and calcium), this did not result in decreased GWG. Additionally, some women were still not consuming 75% of the Recommended daily allowance (RDA) for the key nutrients. Table 5 summarizes the setting and results of the seven intervention studies.

Table 5.  Overview of intervention studies, aiming at decreasing gestational weight
AuthorIntervention populationInterventionControlsPositive effectNo effect
  1. BMI, body mass index; CHO, carbohydrate; EI, energy intake; GWG, gestational weight gain; IBW, ideal body weigh; PA, physical activity; pp, post-partum; RCT, randomized controlled trial.

Borberg et al. (48):
RCT
10 obese pregnant ♀Prescription of a diet containing 1800–2000 calories and 150–180 g of CHO by a dietician9 thin (<80% IBW), 10 normal and 10 obese pregnant (>120% IBW) ♀• ↓ GWG
• Net pp weight loss
• No ↑ skinfold thickness
• Smaller ↑ insulin concentration
• Fasting plasma glucose
• Neonatal outcome
Widga et al. (54):
Randomized trial
40 low-income pregnant ♀, mean
prepregnancy weight 60 kg ± 11.9
In-home nutritional education and counselling26 low-income pregnant ♀, mean prepregnancy weight 63 kg ± 18.9 kg• ↑ Energy, folate, vit B6, iron, zinc and calcium
• ↑ Vegetables and breads/grains
• GWG
• Infant birth weight
Gray-Donald et al. 2000 Prospective controlled trial112 pregnant ♀
mean BMI 29.6 kg m–2
• Dietary advice
• Info through local radio + pamphlets
• Supermarket tours,
• Cooking classes
• Exercise groups
Historical group of 107 pregnant ♀ mean BMI 30.8 kg m–2• ↑ Folate intake
• ↓ Caffeine intake
• GWG
• Plasma glucose
• Dietary intake
• pp weight retention
• Birth weight
• PA
Olson et al. (51): Prospective cohort design131 and 48 pregnant ♀ with, respectively, normal weight and overweight categorized according to income• Monitoring GWG using obstetric chart
• Brochure and Newsletter about GWG and diet self-monitoring tools, PA and diet
Historical group of pregnant ♀↓ Proportion of low-income overweight ♀ with:
• Excessive GWG
• Retaining > 2.27 kg
• GWG
• pp weight retention
in the low-income normal weight group and high-
income groups
Polley et al. (52):
RCT
30 normal-weight (19.8–26.0kg m–2) and 27 overweight (>26 kg m–2) pregnant ♀• Dietary advice
• Monitoring GWG by individual graphs
• PA education
31 normal-weight (19.8–26.0 kg m–2) and 22 overweight (>26 kg m–2) pregnant ♀• ↓ Proportion of normal weight ♀ with excessive GWG
• ↓ pp weight retention for normal weight ♀
• Total GWG
• Fat intake
• PA
• Pregnancy and fetal outcomes
• pp weight loss
• pp weight retention overweight ♀
Kinnunen et al. (53):
Controlled trial
49 pregnant ♀, mean BMI 23.7 ± 3.9 kg m–2Individual counselling on diet and PA56 pregnant ♀, mean BMI 22.3 ± 2.1 kg m–2• ↑ Intake vegetables, fruit and berries
• Smaller ↓ high-fibre bread
• No infants with high birth weight versus 15% in control
• Total GWG
• High-sugar snacks
Wolff et al. (49): RCT23 pregnant ♀, mean BMI 35 ± 4 kg m–210 individual 1-h dietary consultations27 pregnant ♀, mean BMI 35 ± 3 kg m–2• GWG
• ↓ EI with ↓ fat intake, ↑ CHO intake
• Smaller ↑ insulin and leptin concentration
• ↓ Fasting Glucose at 36 weeks
• Neonatal outcome

The positive effects of the intervention studies on nutritional habits should be evaluated critically as pregnant women probably automatically change their behaviour (higher consumption of vegetables and fruit, beef and dairy products) (55–59). Most efforts are generally made to avoid specific, potentially harmful food groups like raw meat and vegetables, reduce alcohol and caffeinated beverages, rather than to improve their diet towards healthy nutrition and controlling GWG (55–59). Obese women still consume a high-fat diet with a low dietary fibre and calcium intake in their first trimester of pregnancy (60). There is particularly an inadequate intake of vitamin D, iron, zinc, calcium and folate and an excessive intake of fat, vitamin A and sodium (57,61–64). The promotion of healthy nutrition therefore remains necessary.

Physical activity

The American College of Obstetricians and Gynecologists recommends that, in the absence of either medical or obstetric complications, pregnant women should perform 30 min or more of moderate exercise everyday. Activities with a high risk of falling or abdominal trauma should be avoided during pregnancy, as well as physical activities at high altitude (65). Because of the benefits, overweight or obese women should be motivated to exercise, starting with light activities such as walking and slowly building up the duration. Three times 10 min a day is suggested to be as effective as 30 min at once (66). Regular exercise, vigorous as well as light-to-moderate physical activity may reduce the risk for pre-eclampsia, abnormal glucose tolerance and gestational diabetes (67–70). However, to confirm the data of a recent paper on the effects of physical activity and pregnancy, more research is needed. The results of Madsen et al. suggest that leisure time exercise during pregnancy, and especially high-impact exercise, increases the risk of miscarriage in the early stage of pregnancy (71).

Post-partum physical activity is also advisable. Next to improving total well-being, a structured diet combined with a physical activity programme helps overweight women to lose the extra weight retained after pregnancy (72,73). However, support from professionals and family is crucial for women to exercise during the post-partum period (72,73).

Unfortunately, up to 60% of the pregnant women are inactive (74). The level of physical activity during the year prior to pregnancy is the strongest predictor of physical activity during pregnancy (75). More than 75% of the women who were active before pregnancy continued to exercise (67). Only 6% of the women who were inactive before pregnancy started physical activity during the first 20 weeks of pregnancy (67). In general, the intensity and duration of both leisure time and work-related physical activity are decreased during pregnancy (74). Data on physical activity among obese pregnant women are scarce. As previous studies have shown that obese women in general have a sedentary lifestyle, one can presume that obese pregnant women are inactive as well (76).

Discussion and conclusion

The prevalence of obesity among pregnant women is rising, exposing the mother and her child to short- and long-term health problems. A causal relationship between the prepregnancy BMI and obstetric complications is proven. If a woman becomes overweight in between two pregnancies (shift from 23 kg m−2 to 25 kg m−2), the risk of developing gestational diabetes during her second pregnancy is doubled compared with the risk during her first pregnancy (34). Inversely, a small decrease in weight (1 BMI unit) results in a decreased risk for macrosomia (34). Weight management is important for every women of reproductive age: women with a normal BMI should strive for maintenance of a healthy weight, whereas overweight and obese women should aim at weight reduction prior to pregnancy. However, majority of the obstetricians (52.8%) consider their training on weight management as ‘inadequate’ or ‘non-existent’ (77). Obese and overweight pregnant women might therefore benefit from regular visits to a dietician who is familiar with the dietary and physical activity recommendations for obese pregnant women. As solid evidence on the safety of weight loss during pregnancy for the infant or mother on the longer term is lacking, the counselling should strive for a healthy lifestyle during pregnancy and a controlled GWG.

Unfortunately, available intervention studies that tried to interfere with GWG through dietary recommendations and closely monitoring GWG do not provide concordant results and show limitations. The prospective controlled trial of Gray-Donald was limited to a specific community and not randomized (50). The Cree population also has specific cultural beliefs concerning diet and physical activity during pregnancy, limiting the validity of their findings in the general population. This is also the case for the study of Polley and Widga, who included only low-income women (52,54). Other limitations of the study of Polley are the relative small sample size and the fact that they had only one dietary outcome, being fat intake (52). The randomized trial of Widga lacked crucial dietary data of the control group and included patients up to 24 weeks (54). The most important limitation of the study by Kinnunen is the randomization in six different clinics, especially since the control clinics and intervention clinics used different GWG recommendations (53).

Further evidence is needed on the optimal GWG in obese and overweight pregnant women and on easy, widely applicable strategies to optimize GWG, healthy eating behaviour and physical activity during pregnancy in this growing group of patients. We will then have made a first but crucial step in stopping the vicious cycle of maternal and childhood obesity.

Acknowledgements

This study was funded by a doctoral scholarship from the Danone Institute Belgium.

Conflict of Interest Statement

No conflict of interest was declared.

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