There is a growing body of research examining just how much of an impact uterine environment has on risk of disease later in life. While the association between malnutrition and fetal outcomes is well understood, undernutrition isn’t the predominant problem for most in the developed world any more!
Just like with underweight mothers, we now understand that higher pre-pregnancy body weight and excessive gestational weight gain significantly increases risk of disease later in life. With over 60% of our population overweight or obese, the impact of prenatal environment presents new and profound challenges in obesity management – if we are “pre-programmed” in the uterus to become obese, what chance do we have of halting the obesity epidemic?
Interest in prenatal nutrition was sparked in 1976 when the Dutch Hunger Winter Study was first published (1). The study followed a small population in the Netherlands that was cut-off from food supplies in the winter and spring of 1944-45. For those women who became pregnant in this time period, their children showed higher rates of obesity and heart disease, as well as a host of other issues, later in life. This first glimpse at the long-term impact of uterine environment led to a new frontier in research – the developmental origins of disease – or what we affectionately refer to as “when in doubt, blame your mother!”
Women who are obese prior to conception are at significantly higher risk for a variety of medical and obstetric issues including miscarriage, gestational diabetes and hypertension, as well as delivery complications at caesarean delivery (2). While these risks are well-documented in prenatal guidelines, a growing body of research shows time and time again that the impact of maternal obesity lasts long after birth and, in fact, persists into adulthood. Maternal obesity has been linked to an increased offspring risk of the most common chronic diseases: obesity, diabetes, heart disease and possibly even cancer (2).
In a birth cohort in Israel, both higher pre-pregnancy BMI and greater gestational weight gain were significantly associated with a host of cardiometabolic risk factors at the follow-up age of 32 years (3). In addition to higher body weight, offspring also had more abdominal fat, higher blood pressure, more circulating insulin and triglycerides, and lower HDL cholesterol when mom’s prepregnancy BMI was > 26 and weight gain was > 14 kg (30 lbs) vs. those with a BMI < 21 and weight gain < 9 kg (20 lbs).
Currently, the Canadian Prenatal Nutrition Guidelines recommend the following for gestational weight gain based on pre-pregnancy BMI (for singleton pregnancy):
- BMI < 18.5: 12.5 – 18 kg (28 – 40 lbs)
- BMI 18.6 – 24.9: 11.5 – 16 kg (25 – 35 lbs)
- BMI 25 – 29.9: 7 – 11.5 kg (15 – 25 lbs)
- BMI > 30: 5 – 9 kg (11 – 20 lbs)
Over half of Canadian adults are overweight or obese, with nearly 30% having a BMI of over 30 – gone are the days of “eating for two”! While dieting for weight loss during pregnancy was previously a no-no, new findings suggest “judicious” diets may do more good than harm. In fact, a new meta-analysis shows that encouraging calorie control and lower-than-recommended weight gain dramatically reduces risk of complications during pregnancy and a healthy diet seems to be the best method to control weight (4). Among studies where calorie control was emphasized to reduce gestational weight gain, in those who were overweight/obese at conception, pooled results showed a 33% lower risk of pre-eclampsia, 60% lower risk of gestational diabetes and 70% reduced risk of gestational hypertension – all of which are known to adversely affect the health of their children.
Many experts now believe that the above guidelines, with respect to weight gain during pregnancy, may be too generous for those in the upper weight ranges. Rather than blanket target weight gain ranges, weight gain recommendations should be individualized in discussion with physicians given the high risk of short- and long-term complications with excessive body weight during pregnancy (5). Unfortunately, a recent Canadian study showed that only 12% of 310 women surveyed reported being counselled on how much weight to gain during their pregnancy (6).
We have really just scratched the surface with respect to what fetal programming research may tell us about the development of chronic diseases. Furthermore, the impact of uterine environment has been implicated in a multitude of other conditions, as demonstrated by animal models. Links have been found between maternal stress and increased risk of anxiety and depression; nausea/vomiting early in pregnancy and “salt craving”; maternal junk food diet and preference for junk food later; and the list just keeps on growing!
No Baloney’s advice? An ounce of prevention is worth a pound of cure! If you are thinking about becoming pregnant, achieving and maintaining a healthy body weight *before* you become pregnant is important not just for your own health, but for that of your future child… into their adult years too! But life tends to just happen sometimes – if you find out you are pregnant and are concerned about your weight, talk to your doctor about what a healthy amount of weight gain would be for you.
Setting goals early in pregnancy, with respect to modest weight gain, will play an increasingly important role in prenatal care. Weight gain at 24 weeks is a strong predictor for the development of gestational diabetes – women should really gain no more than 2 kg of weight during the first trimester. Think of it this way – when your fetus is literally the size of a “.”, increases in energy requirements are pretty small!
We know that many women gain more weight than they need to during pregnancy – more than 30% gain excessively, particularly if they are overweight or obese at conception (7) – yet intake of protein, carbohydrates, calcium, iron, folate and fibre may remain inadequate despite these excess calories (8,9). Obviously education needs to be about more than just calories – nutrient density if key. The Canadian Prenatal Guidelines from 2009 are getting a facelift this year – stay tuned for the release.
The Alberta Pregnancy Outcomes and Nutrition (APrON) study is currently running. For more information:
- APrON: the largest prenatal nutrition study in Canada, the focus of this longitudinal study is on nutrition and infant/child mental and neurodevelopmental outcomes
- Fetal Programming Study: a sub-study of APrON, this study is investigating the impact of maternal stress on infant stress response and coping
- Schulz LC. The Dutch Hunger Winter and the developmental origins of health and disease. Proc Natl Acad Sci USA 2010; 107:16757-8.
- Aviram A, Hod M, Yogev Y. Maternal obesity: implications for pregnancy outcome and long-term risks-a link to maternal nutrition. Int J Gynaecol Obstet 2011;115 Suppl 1:S6-10.
- Hochner H, et al. Associations of maternal prepregnancy body mass index and gestational weight gain with adult offspring cardiometabolic risk factors: the Jerusalem Perinatal Family Follow-up Study. Circulation 2012;125:1381-9.
- Thangaratinam A, Rogozinska E, Jolly K, et al. Effects of interventions in pregnancy on maternal weight and obstetric outcomes: meta-analysis of randomised evidence. BMJ 2012; 344 [epub ahead of print].
- Artal R, Lockwood CJ, Brown HL. Weight gain recommendations in pregnancy and the obesity epidemic. Obstet Gynecol. 2010; 115:152-5.
- McDonald SD, et al. Despite 2009 guidelines, few women report being counseled correctly about weight gain during pregnancy. Am J Obstet Gynecol. 2011; 205:333.e1-6.
- Herring SJ, Rose MZ, Skouteris H, Oken E. Optimizing weight gain in pregnancy to prevent obesity in women and children. Diabetes Obes Metab 2012; 14:195-203.
- Byrne NM,Groves AM, McIntyre HD, Callaway LK; BAMBINO group. Changes in resting and walking energy expenditure and walking speed during pregnancy in obese women. Am J Clin Nutr 2011; 94:819-30.
- Brooten D, et al. Perceived weight gain, risk, and nutrition in pregnancy in five racial groups. J Am Acad Nurse Pract 2012; 24:32-42.