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Diet and lifestyle

Pregnant women becoming increasingly overweight

New Danish research shows that the body mass index (BMI) of pregnant women is increasing over the years. Their newborn babies are also becoming larger, which increases the child’s risk of becoming overweight. A researcher is concerned.

Pregnant women in Denmark are becoming increasingly overweight over the years. The percentage of pregnant women in Denmark with a prepregnancy BMI (weight in kg/(height in metres)2) exceeding 25, which is the threshold for overweight, rose to 34% in 2012. The percentage of pregnant women who were obese (BMI > 30) before pregnancy reached 13% in 2012.

Women who are overweight during pregnancy often give birth to overweight babies. These children have an increased risk of becoming obese throughout their lives, in a vicious circle that currently seems endless.

Overweight women also have a greater risk of experiencing all kinds of problems in pregnancy, including pre-eclampsia, and they frequently have problems during childbirth requiring caesarean section, vacuum extraction or forceps.

“Since we know that being overweight during pregnancy is associated with so many problems, it is alarming to see that pregnant women in Denmark are becoming increasingly overweight as the years go by. Unfortunately, this does not just apply to pregnant women but permeates society as a whole,” explains Per Ovesen, Consultant Obstetrician, Aarhus University Hospital and Professor, Department of Clinical Medicine and Department of Obstetrics and Gynaecology, Aarhus University.

The new study was published in Acta Obstetrica Gynecologica Scandinavica.

Overweight pregnant mothers have overweight babies

The study examined a cohort from the Danish Medical Birth Registry including all women in Denmark who gave birth in 2004–2012. During this period, the Registry recorded data from 572,321 births, corresponding to 99.8% of all births in Denmark. The percentage of pregnant women who were overweight increased from 31.9% in 2004 to 34.2% in 2012, and the percentage who were obese increased from 11.0% to 12.8%.

“These are tremendous increases, but they reflect the general trend in society, which unfortunately is that more and more of us are becoming overweight,” explains Per Ovesen.

The problem with pregnant women being overweight is that there are no benefits. When a mother is overweight and overeats during pregnancy, the baby also gets bigger, but the birth canal through which the child has to pass during delivery does not get bigger. Some newborns simply end up being too big to be born naturally.

“Unfortunately, we have created a trend in which heavier mothers give birth to heavier children, who then become heavier mothers, who in turn give birth to even heavier children. This is not good,” says Per Ovesen.

Gaining more weight for each pregnancy

Per Ovesen’s research also shows that giving birth to more children exacerbates the problems.

Women naturally gain weight during pregnancy, but unfortunately few revert to their original weight. The more children they have, the more overweight they become.

“In extreme cases, women gain 20 kg per pregnancy but lose only 10 kg afterwards. This is not good. Women need to revert to their previous weight after giving birth. If women give birth to three children, over the three pregnancies they could end up gaining 30 kg, and that is unhealthy,” says Per Ovesen.

Multiple births increase the risk of type 2 diabetes

Connecting these new research results with other research from Per Ovesen’s group makes the problems even more obvious.

Another study from the research group has shown that giving birth more times increases the risk of developing type 2 diabetes. It simply happens because women gain weight during each pregnancy without losing it afterwards, and obesity is inextricably linked to the risk of developing various metabolic disorders.

The same risk applies to the next generation.

Women usually become insulin resistant during pregnancy. This corresponds to a mild form of diabetes.

The placenta ensures that pregnant women become insulin resistant, so that they do not absorb sugar from the food they eat, diverting it to the fetus instead.

This evolutionary mechanism made very good sense 10,000 years ago when food was often scarce and infant mortality was high. Today, the mechanism just produces heavier babies because many pregnant women eat more than they and their unborn baby actually need.

“It is pure evolution theory, and it worked very well then, but now it is really bad,” says Per Ovesen.

Breastfeeding to lose the weight

The worldwide trend is that people are becoming increasingly overweight, and although Denmark has a major problem, many other countries have even greater problems. The United States and Mexico are perhaps the most obvious examples of countries that are really struggling with runaway obesity epidemics.

According to Per Ovesen, reversing the epidemic requires measures that can break the vicious circle of overweight mothers giving birth to overweight children.

Women need to be informed that they should revert to their original weight after giving birth and should not accept being 5 or 8 kg heavier. The next time they get pregnant, they might gain even more weight, and eventually their children will pay the price by passing on the mother’s legacy to their children in the form of overweight.

“The best way for women to tackle this is to breastfeed. Breastfeeding women burn large amounts of energy, and they produce milk that also depletes energy and diverts it into their newborn baby. In addition, women should not just sit on the couch and eat unhealthy food but instead get out and take long walks so that they can get their bodies back in shape and ready to get pregnant again,” explains Per Ovesen.

Fortunately, Per Ovesen's research has shown that pregnant women who get the right information are rapidly motivated to ensure the health of their unborn child, making it easier for them to be healthy during pregnancy.

Unfortunately, this house of cards may collapse when women have to take care of themselves and shed the excess weight after giving birth. Many still struggle with that.

Associations between parity and maternal BMI in a population-based cohort study” has been published in Acta Obstetrica Gynecologica Scandinavica. The Novo Nordisk Foundation awarded Per Glud Ovesen, Professor, Department of Clinical Medicine and Department of Obstetrics and Gynaecology, Aarhus University, a grant in 2015 for the project Overweight, Diabetes and Pregnancy: the Effects on Birth and Pregnancy and on the Risk of the Mother and Child of Developing Obesity and Type 2 Diabetes Later in Life.

Per Glud Ovesen
Professor, Dr. med.
There are no private clinics in this community. All pregnant women (5000 per year) are therefore controlled at this this department: normal pregnant women by the midwifes, and pathological pregnancies by midwifes and doctors in collaboration. Less than 1% deliver at home and the absolute majority of these assisted by a midwife from this clinic. Perinatal Research Unit: The Aarhus Birth Cohort includes almost 100.000 pregnancies from this department. This comprehensive dataset is continually validated by research midwifes. Maternal fetal medicine More than 95% of the population accepts double test and nuchal translucency scan at week 12 in addition to anomalyscan in week 19. These scans and indicated scans are registered in the Astraia database. Research laboratory: One full time technician ensure the quality. Biochemical analyses of collagen and other connective tissue components. qPCR. Myographs for assessment of smooth muscle contractility. Biobank in which two technicians obtain blood from a large fraction of the pregnant women, their partners and the umbilical cord of the newborn baby. Clinical studies RCT have high priority The collaboration with the MRI department is well established All diabetic mothers are registered in a database