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Can Low Glycemic Diet Increase VBAC Success?
Cohain JS. firstname.lastname@example.org
MIDIRS Midwifery Digest 2009:19:71
Strong association has been documented between failed trial of labor
after cesarean surgery and birth weight over 4000g. There is evidence that
diets containing only low glycemic carbohydrates produce babies with birth
weights in the 25-50 percentile range. Regular exercise is associated
with an increase in placental growth and function and a decrease in birth
weight. It is therefore a feasible that motivated women may choose
to adopt a low glycemic diet and exercise programme in pregnancy in order
to limit the birth weight of their fetus without apparent harm to the baby,
in order to increase likelihood of vaginal birth and successful VBAC.
Introduction and background literature
Given the known risks associated with attempting VBAC,identifying those women for whom VBAC is likely to be successful as well as minimizing possible complications, is of paramount importance. Eight large studies found that trials of labor (TOL) when the birth weight was over 4 kilo was a significant factor for failure to achieve VBACs (1-8).
The research studies conclude that women with birth weight estimations above 4250 g(2), women with BMI >40.0 kg/m2 (6) and women with weight gains over 40 pounds during pregnancy(7) should be carefully counseled as to the risks of unsuccessful VBAC before choosing this as an option This is particularly relevant when the reason for the previous CS was either Cephalo Pelvic Disproportion (CPD) or failure to progress and where there is no history of previous vaginal births.(2) Higher rates of uterine rupture are associated with birth weights > 4000 g. Three studies found higher rates of uterine rupture with larger babies, this ranged from : 1.6% for over 4000 g (1); 3.6% for >= 4000 g in a group with no previous vaginal delivery(2); and 2.4% for over 4250 g.(1). Hibbard (7) studied the relationship of uterine rupture to mother’s BMI rather than birth weight and found morbidly obese women ( BMI>=40) , had higher combined rates of rupture / wound dehiscence as well as an increased risk of neonatal injury. On the other end of the spectrum, two studies found significantly lower uterine rupture rates in VBACS with babies of birth weights below 2500g (9,10).
Bianco (11) noticed that weight gains of more than 25 lb were strongly associated with birth of a large for gestational age (LGA) neonate, however, poor weight gain did not appear to increase the risk of delivery of a low birth weight neonate. This suggested that maternal weight gain per se, in contrast with the type of maternal carbohydrate intake, was not useful as a prediction of birth weight.
Clapp (12) has intensively studied the relationship between the type and frequency of carbohydrate intake during pregnancy and exercise on maternal blood glucose levels and insulin sensitivity. The delivery of oxygen and food to the placenta are major factors in fetal and placental growth or lack thereof. Restrictions in maternal energy intake reduce maternal blood sugar levels having the effect of decreasing fetal growth rate and fetal size at birth. During pregnancy, sustained exercise sessions cause a temporary reduction in oxygen and food to the placenta, sometimes at levels of up to 50%, but this is thought to be compensated by improved oxygen and food delivery at rest. Research findings suggest that regular exercise is associated with an increase in placental growth and function and a decrease in birth weight (13)
As noted above, it has been noted that the type of carbohydrate intake directly influences birth weight and maternal weight gain, by influencing maternal blood glucose levels and insulin sensitivity. Clapp sets this out very clearly and his definition of low-glycemic sources vs. high glycemic sources are reproduced in Table 1. This is not entirely straightforward as the accompany notes suggest
Table 1. Typical low- and high-glycemic-carbohydrate food sources
Low-glycemic sources High-glycemic sources
Whole grains & unprocessed rice Processed grains: flour,bread,cereal
Beans & non-tuberous vegetables Tuberous vegetables:Potato,Carrot,Parsnip
Pasta unless overcooked* Typical desserts, baked goods, confectionery
Most fresh fruits & unsweetened juices** Soft drinks, sweetened juices
Unsweetened chocolate Other snack foods
Dairy products Ripe bananas, tropical fruit
*Since pasta is flour and water, it is curious why pasta is on low-glycemic side
** Presumably in limited quantities, since fruit contains simple sugars
Eating primarily high-glycemic carbohydrate results in feto-placental overgrowth and excessive maternal weight gain, while intake of low-glycemic carbohydrate produces infants with birth weights between the 25th and the 50th percentile and normal maternal weight gain.
Clapp’s study showed that women who reported eating carbohydrates mainly of low-glycemic index gained less weight and had smaller babies than women who ate primarily high glycemic types of carbohydrates. When he randomized women to a high or low glycemic , the women who were randomized to the high glycemic diet had increased 1,2 and 3 hour postprandial glucose levels and insulin levels throughout pregnancy. They experienced larger weight gain and symmetrically larger infants and placentas. Interestingly, total calorie intake was 14% more on the LOW glycemic index diet. The data indicate that a large part of the normal variance in birth weight is related to differences in type of maternal dietary carbohydrate intake. Low-glycemic food sources in the diet decrease growth rate and size at birth while high-glycemic food sources increase it. Thus, extrapolating the findings to current care in pregnancy, in the absence of severe malnutrition, it may be possible to decrease the need for cesarean surgery in both healthy, low-risk women and a variety of high-risk populaces by simply modifying maternal physical activity and the type of carbohydrate eaten during pregnancy.
Despite the above scientific evidence, none of the eight papers associating 4000g babies with failed TOL, proposed low glycemic diets as a possible means to prevent VBAC failure One possible explanation is that both practitioners’ and researchers’ consider pregnant women unable to discipline themselves as far as diet and exercise, or perhaps even more worrying, that such an essential aspect as diet and nutrition, is not actually considered part of medical enquiry into well being and preventive health measures. At the same time as dismissing women as unable to diet, or advising them against it, women are warned that dieting will produce a birth weight <2500g, which will increase the risk of stillbirth. This builds on the myth that bigger is always better /healthier, perhaps also confusing a smaller size as indicating poor growth and less healthy (small for gestational age SGA) without examining the cause. Such approaches do not reflect the current scientific evidence nor does it reflect the potential role for inquiry into the make up of the woman’s prepregnancy nutrition or diet during pregnancy,.
SGA babies are known to have a higher stillbirth rate and higher morbidity and mortality rate after birth.(14) The diverse causes of SGA in babies range from heart malformations, blood disorders, viral infections, smoking, drug abuse, anemia and malnutrition . (15,16). Neither stillbirth nor IUGR have been associated with balanced, low glycemic diets in singleton pregnancies, not complicated by smoking, drug abuse or prepregnancy malnutrition.(17) When prepregnancy malnutrition is present, high energy intake is associated with a reduced risk of preterm birth (18). A seminal study of pregnant women affected by near starvation diets during the third trimester as a result of the German military regime at the latter part of the Second World War found a clear reduction in fetal growth, but no effect on gestational duration (17) Dr GC Smith (18) in a careful summary of the sparse knowledge in the western literature regarding fetal growth impairment identified the following
1. Small CRL measurements on first trimester ultrasounds appear to have some ability to predict low birth weight babies (<2500 g). (No connection made to diet.)
2. A suboptimal environment in the first trimester may permanently affect the fetus to restrict its growth potential. However, it is unknown whether a suboptimal environment is connected to diet and/or genetics of the mother and/or fetus and/or environmental influences and if so which?
The only evidence directly relating diet and poor outcomes is a single study in sheep who were either fed ad lib or undernourished to reduce the sheep’s weight by 15% from 60 days before until 30 days after conception (term= 145 days) comparable to a woman losing 20 pounds during the 2 months before conception (19) Periconceptual under-nutrition in sheep was associated with an increased risk of noninfectious preterm birth possibly related to premature activation of the fetal hypothalamic-pituitary-adrenal axis. In layman’s terms this translates into long term starvation diets causing long-term adrenaline/cortisol release by the fetus causing preterm labor. This can hardly refer to obese women eating brown rice instead of white bread, or eating a peach instead of half a cake with chocolate icing.
To date, after the first trimester, excessive exercise and restricted diets have not been associated with premature births or stillbirths in women with good prepregnancy nutrition. Fear that limiting calorie intake during the second and third trimesters will result in increased risk of stillbirth has no basis for women with excellent prepregnancy nutrition., Infact, stillbirth is associated with the morbidly obese (20).
Support that limiting intake of simple sugars can decrease birth weight without sacrificing safety or increasing stillbirth has been supported in the past two decades in Japan where there are general recommendations for minimal sugar and fruit intake. In 1997, the Japan Society of Obstetrics and Gynecology (JSOG) issued guidelines for optimal weight gain during pregnancy, which are based on prepregnancy BMI (21). Recommended weight gains are
10–12 kg for women of BMI < 18.0,
7–10 kg for women of BMI 18.0 to 24.0, and
5–7 kg for women of BMI > 24.0.
. These guidelines are widely promoted at prenatal visits(22) in a compelling manner. In 1975, 5.5% of all infants born weighed less than 2,500 g, while in 2003, this almost doubled to 10.1%. Term birth weight less than 2,500 g is defined as SGA. The mean birth weights have gradually declined from 3.23 to 3.16 to 3.07 kg for boys and 3.14 to 3.08 to 2.99 kg for girls from 1980 to 1990 to 2000. Macrosomia (defined as 4.0kg or more) has decreased in Japan from 3% to 1% in the past 20 years.(23) In the presence of the weight gain restrictions, the unexplained stillbirth rate is remarkably low. The unexplained stillbirth rate in Japan was about 0.9/1000 for the years 1998-2005.(24) This figure is 300% less than the unexplained stillbirth rate in the UK during the same period.(3.9/1000)(24). If simple sugar and calorie restriction were causes of stillbirth, this would likely be reflected in the Japanese stillbirth rates. Prematurity and growth restriction are the most commonly associated factor of unexplained stillbirths, in Japan, as it is in every country in which stillbirth is carefully studied(24) The experiences in Japan support healthy, low sugar diet as a means to produce smaller, healthier babies for the purpose of successful VBAC, without increased risk of stillbirth or prematurity. Based on their excellent data, it would be difficult, at best, to argue that calorie restriction in the second and third trimester for women with BMI over 25 is responsible for increased stillbirth due to growth restriction. Dietary restriction in Japan may even be associated with or the cause of the relatively low 0.71% rate of diabetic pregnancy in Japan (25) compared to the US rate of 4% of all pregnant women.(26).
It has been argued that the decision to offer VBAC on the basis of fetal
weight estimation is questionable because: “Ultrasonography has a known
margin of error in the third trimester, making counseling for VBAC on the
basis of estimated fetal weight difficult.” (11). Despite the known margin
of error of ultrasound, for the purposes of predicting decreased risk,
it is only necessary to determine whether the baby is closer to 2.5 kilo
or 4 kilo, and therefore it is reasonable to consider that ultrasound is
a useful tool for determining likelihood of VBAC success.
Case Study ( the name has been altered to protect confidentiality)
Heather was a 29 year old Caucasian, Gravida 4, Para 3 with a history of three previous cesarean sections and an otherwise uneventful medical history . I first met her when she was 12 weeks pregnant. She expressed a strong desire for a vaginal birth. At this first visit, with a height of 5’2” and a weight of 152 pounds (69kilos) she had a BMI of 27.8.
Her obstetric history showed two past cesareans for failure to progress and one for a non-reassuring fetal heart tones. . Her first pregnancy resulted in a live boy with a birth weight of 3900 g. at 39 weeks gestation, born by emergency cesarean surgery after pitocin augmentation, AROM and epidural anesthesia, and failure to progress after 20 hours of labor. Her second pregnancy resulted in a live male with a birth weight of 3900 at 40 weeks gestation by emergency cesarean surgery, after prostaglandin augmentation, AROM and epidural anesthesia, and again, failure to progress after 20 hours of labor. Her third pregnancy resulted in a live male with a birth weight of 3500 g. at 40 weeks gestation, by emergency caesarean surgery for non-reassuring heart rate after 15 hours of labor. During the third labor she was 8 cm dilation before surgery. She had no known allergies, a blood type of O+ and a hemoglobin level of 13.3 gm/dl at 18 weeks. She was immune to rubella and varicella and screening tests for hepatitis, syphilis, and HIV were negative. Her fasting blood sugar was 91 and her Hgb A1C was non-diabetic at 18 weeks. Her blood pressure was normotensive.
Therefore, other than her history of cesarean births, her medical and obstetric history were uneventful and as noted above, she had a strong desire to deliver vaginally. The one aspect we felt could be looked into was the large birth weights of her babies in the absence of any signs of gestational diabetes. The aim was for her to have a smaller baby to reduce the risk of uterine rupture around the time of birth and improve her chances of a vaginal birth!
After our initial consultation, starting at 13 weeks gestation, she ate no fruit or sugar trying to keep as close as possible to 1000 to 1200 calories per day and 50 grams of protein. Her choice of intake was the following accompanied by regular exercise:
For breakfast, she ate a cup of Grape-nuts cereal with cup of milk (32 gm protein/500 calories) followed by a walk.
For lunch she ate no food, took her prenatal vitamins with iron and followed by a protocol of leg lifts, weight lifting of arm weights and stomach toning exercises. For dinner, she ate either chicken or sushi. The chicken dinner consisted of 2 chicken legs and rice (21 gm protein/500 calories), occasionally adding fresh or cooked vegetables.
She followed a regimen of twice weekly kick boxing until 6 months into her pregnancy
When labor started spontaneously she had gained 13 pounds (6 kilo) therefore now weighing 165 pounds (75 kilo). At 25 weeks her placenta was found to be posterior and when she went into labor , the position of the placenta was rechecked by US and confirmed to still be posterior.
At 38+0 weeks, Heather presented with SROM, clear fluid and contractions every 20 minutes. Intermittent auscultation every 15-30 minutes found reassuring fetal heart tones, no action was taken to augment the labour and observations were undertaken to ensure all was well. Eight hours after SROM, her contractions increased to every 7-10 minutes, and subsequently progressing to three minute intervals. No vaginal examinations were performed. She maintained a regular fluid intake of water, drinking about a litre every fours hours. She had a 20 minute second stage and gave birth to a baby girl, vaginally, with an intact perineum. A normal placenta was expelled five minutes later accompanied by estimated blood loss of 20 cc. The baby girl had a birth weight of 2500 grams, and Apgars of 10/1,10/5. There was an uneventful postpartum period and the baby was normal on pediatric examination. After the birth she wrote: “Thank you for the patience, knowledge and skill that you shared with me these past 6 months. You quelled a nightmare that has haunted me for seven years.”
Conclusion: This global statement that dietary restriction during pregnancy is dangerous, without a deeper look into prepregnancy nutrition and the makeup of the diet, is not grounded in science, or supported by scientific evidence gained from contemporary clinical care .
For women with free access to high glycemic foods, food choices are
necessary throughout the day to attain optimum birth outcomes. This particularly
applies to women with a history of cesarean surgery with no previous vaginal
births and a history of failure to progress. The case study demonstrates
that for one woman, with excellent prepregnancy nutrition, BMI>25, and
excellent first trimester nutrition, motivation to maintain a low glycemic
diet, quality protein intake and daily exercise in the second and third
trimester, with appropriate support resulted in a reduced birth
weight without affecting the baby’s overall well being . More research
into VBAC outcomes in the presence of low glycemic foods is urgently needed
especially in the context of concern about obesity in the resource rich
countries. That such a relatively simple initiative could have such
positive outcomes should be of interest to the medical and midwifery community.
In the light of no overt untoward effects, it is proposed that this
has the potential to be an effective method to increase the VBAC success
rate. This case proves that there do exist women who are motivated
enough to pursue such an option.
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2. Elkousy MA, Sammel M, Stevens E, Peipert JF, Macones G. The effect of birth weight on vaginal birth after cesarean delivery success rates. Am J Obstet Gynecol. 2003;188(3):824-30.
3.Juhasz G, Gyamfi C, Gyamfi P, Tocce K, Stone JL. Effect of body mass index and excessive weight gain on success of vaginal birth after cesarean delivery. Obstet Gynecol. 2005;106(4):741-6.
4. Gyamfi C, Juhasz G, Gyamfi P, Stone JL. Increased success of trial of labor after previous vaginal birth after cesarean. Obstet Gynecol. 2004;104(4):715-9.
5. Landon MB, Leindecker S, Spong CY, Hauth JC, Bloom S, Varner MW, Moawad AH, Caritis SN, Harper M, Wapner RJ, Sorokin Y, Miodovnik M, Carpenter M, Peaceman AM, O'Sullivan MJ, Sibai BM, Langer O, Thorp JM, Ramin SM, Mercer BM, Gabbe SG; National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. The MFMU Cesarean Registry: factors affecting the success of trial of labor after previous cesarean delivery. Am J Obstet Gynecol. 2005;193(3 Pt 2):1016-23.
6. Goodall PT, Ahn JT, Chapa JB, Hibbard JU. Obesity as a risk factor for failed trial of labor in patients with previous cesarean delivery. Am J Obstet Gynecol. 2005;192(5):1423-6.
7. Hibbard JU, Gilbert S, Landon MB, Hauth JC, Leveno KJ, Spong CY, Varner MW, Caritis SN, Harper M, Wapner RJ, Sorokin Y, Miodovnik M, Carpenter M, Peaceman AM, O'Sullivan MJ, Sibai BM, Langer O, Thorp JM, Ramin SM, Mercer BM, Gabbe SG; National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. Trial of labor or repeat cesarean delivery in women with morbid obesity and previous cesarean delivery. Obstet Gynecol. 2006;108(1):125-33.
8. Gregory KD, Korst LM, Fridman M, Shihady I, Broussard P, Fink A, Burnes Bolton L. Vaginal birth after cesarean: clinical risk factors associated with adverse outcome. Am J Obstet Gynecol. 2008;198(4):452.e1-10
9. GC Smith, personal communication. Unpublished data shows “ 0.1% uterine rupture rate among 1000 VBACS birth weight under 2500 g” from the Scottish Morbidity Record (1980–98) and the Scottish Stillbirth and Infant Death Enquiry (1985–98).
10. Quiñones JN, Stamilio DM, Paré E, Peipert JF, Stevens E, Macones GA. The effect of prematurity on vaginal birth after cesarean delivery: success and maternal morbidity. Obstet Gynecol. 2005;105(3):519-24.
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Low-glycemic low-sugar diet and daily exercise to increase VBAC Success
Cohain JS. Can Low Glycemic Diet Increase VBAC Success? MIDIRS Midwifery Digest 2009.19(1)71-75. Full text with references available from: email@example.com or
One in every 50 women after one CS, who is pregnant with a baby weighing 4200g, who attempts VBAC, will have a uterine rupture.
One in every 1000 women after one CS, who is pregnant with a baby weighing 2500g, who attempts VBAC, will have a uterine rupture.
From this we learn a rather obvious truth: that the larger the baby, the more likely the uterus is to rupture while attempting VBAC. This simple truth has been largely ignored because of the American disbelief in the ability of women to control their dietary intake during pregnancy. [Ed: I'm still waiting to get references from Judy about this statement.] In addition, there is a generalized fear that calorie restriction will cause stillbirth and miscarriage, when this has never been documented to be the case for women with adequate protein and vitamin intake. Although there is some evidence showing severe preconception dietary restriction to be associated with miscarriage and stillbirth, evidence is lacking for bad outcomes of any sort when calorie restriction in the presence of adequate protein and vitamins is used in the 2nd and 3rd trimester to make a smaller baby.
To lower the risk of uterine rupture, starting at 12 weeks of pregnancy a woman can eat a low-glycemic, no-sugar diet, with 50 g of daily complete protein and a prenatal vitamin combined with an hour of daily exercise which will lower her blood sugar on a daily basis, thereby producing a 2500-3000 gm baby, greatly lowering her risk of uterine rupture while attempting a VBAC.
There is no research showing any damaging effect of a low-sugar diet in the 2nd and 3rd trimesters. Experience in Japan supports the usefulness of such a diet. Since 1990, strict guidelines for optimal weight gain during pregnancy, based on prepregnancy BMI have been enforced:
10–12 kg for women of BMI < 18.0,
7–10 kg for women of BMI 18.0 to 24.0, and
5–7 kg for women of BMI > 24.0.
In the past 20 years, birth weights have been decreasing in Japan. There has been no concomitant report of increase in miscarriage or stillbirth. In the presence of the weight gain restrictions, the unexplained stillbirth rate is remarkably low. The unexplained stillbirth rate in Japan was about 0.9/1000 for the years 1998-2005. This figure is 300% less than the unexplained stillbirth rate in the UK during the same period.(3.9/1000). Japan enjoys a lower rate of gestational diabetes: Dietary restriction in Japan may even be associated with or the cause of the relatively low 0.71% rate of diabetic pregnancy in Japan compared to the US rate of 4% of all pregnant women.
This diet is best applied to women with a good preconception nutritional intake, BMI>25 a history of Failure to Progress and a desire to deliver vaginally.
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