A long cord could lead to impaired umbilical cord blood flow and an increased risk of fetal entanglement [ 19 ] and is also associated with increased risk of both umbilical thrombosis and umbilical knot.
Why maternal obesity is associated with a longer umbilical cord is unclear. Data from animal studies suggest that cord length is at least partly determined by tensile forces, and fetuses with less amniotic fluid usually have shorter umbilical cords [ 37 ]. There is a positive association between maternal BMI and fetal weight [ 39 ], indicating a larger potential of growth for fetuses to obese women, which could potentially affect the growth of the umbilical cord too.
The risk of umbilical cord thrombosis increases with a hyper coiled cord; both of which may impair cord blood flow and increase the risk of stillbirth [ 18 ]. Cord insertion is established in a very early phase of embryonal development [ 40 ], and it is thus likely that abnormal cord insertions are due to adverse impact in the very beginning of pregnancy in obese women.
A study analyzing cause-specific stillbirth from gestational week 16, stratified by maternal BMI, identified placental dysfunction, umbilical cord complications and hypertensive disorders as important risk factors for stillbirth in obese women [ 14 ].
However, pathophysiological mechanisms behind the increased risk of stillbirth in obese pregnancies are likely complex and may vary with length of gestation [ 14 ]. In the present study, there were no differences in primary cause of death in term stillbirths of women with and without obesity. However, it must be borne in mind that cause of stillbirth, especially at term, is often multifactorial and accurate determination of primary cause of death is not always straightforward.
Moreover, the classification [ 21 ] is based on clinical criteria and experience and the specific significance of each contributing risk factor cannot always be exactly assessed or quantified. To what extent umbilical cord abnormalities contribute to the cause of stillbirth may differ between cases.
To what degree cord abnormalities may be detected in utero is unclear. Ultrasound is a good method for detection of abnormal cord insertion, although a larger proportion of abnormal cord insertions were correctly identified during the second trimester compared to the third trimester [ 41 , 42 ]. Magnetic resonance imaging MRI has also been tested to measure umbilical cord length.
However, measurements using MRI were unreliable with risk of overestimation of the umbilical cord length especially in case of long umbilical cords [ 43 ]. Research on determination of degree of coiling in utero is scarce, however ultrasound may be a possible method [ 28 ].
There is a need for development of techniques to more accurately identify umbilical cord abnormalities in utero. The stillbirth incidence is low and trying to predict stillbirth will lead to low positive predictive values.
All possible predictive models will lead to investigations or extra surveillance of a large number of women among whom very few will suffer from stillbirth. Hence, methods of extra surveillance must be safe and not cause too much anxiety. Our study showed that inflammation tended to be a mediator on the pathway from BMI to stillbirth. Obesity is associated with increased levels of inflammatory markers [ 44 ].
This in turn contributes to the increased risk of hypertensive disorders and other common complications in pregnancies with obesity [ 44 ].
It is also possible that inflammation associated with obesity contributes to the increased risk of stillbirth. In an animal model, it was demonstrated that high-fat-diet during pregnancy increased placental inflammation and decreased uteroplacental perfusion, regardless of obesity. High-fat-diet combined with obesity further decreased blood flow on the fetal side of the placenta and compromised placental function [ 45 ].
An association between chronic chorioamnionitis and preterm stillbirth potentially associated to maternal anti-fetal rejection has been found [ 46 ]. To what degree this could contribute also to term stillbirth is an open question.
We hypothesized that a part of the increased risk of stillbirth in obese women could be explained by an increased risk of chronic fetal hypoxia.
Maternal obesity is associated with fetal hyperinsulinemia, which is an independent risk factor for fetal hypoxia [ 12 , 13 ]. However, the odds ratio for stillbirth in obese women remained unchanged when placental lesions associated with chronic hypoxia were adjusted for. This may be interpreted as chronic hypoxia not being an important risk factor for stillbirth in obese pregnancies or that ordinary placental analyses are too blunt to disclose more subtle changes of chronic hypoxia.
Continued research on mechanisms behind the increased risk of stillbirth among obese women is needed, as well as more knowledge about technics to identify abnormal cords in utero. Umbilical cord abnormalities may account for approximately one fourth of the effect of obesity on the risk of stillbirth at term. We would like to thank Stockholm Stillbirth Group for a fantastic and assiduous work with collection and categorization of all cases of Stillbirth during very many years.
We would also like to thank Anette Niklasson, Annica Westlund and Dragana Knesevic at the Section of Pathology at Huddinge hospital for their invaluable contribution of preparation of all the placentas.
Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Abstract Objective The aim was to explore the potential role of the placenta for the risk of stillbirth at term in pregnancies of obese women. Methods This was a case-control study comparing placental findings from term stillbirths with placental findings from live born infants.
Results A long and hyper coiled cord, cord thrombosis and velamentous cord insertion were stronger risk factors for stillbirth in obese women compared to normal weight women. Conclusion Approximately one fourth of the effect of obesity on the risk of stillbirth in term pregnancies is explained by umbilical cord associated pathology.
Competing interests: No authors have competing interests. Introduction Stillbirth is the main contributor to perinatal death in high income countries. Material and methods This is a case control study. Statistical analyses Maternal characteristics were compared between cases of stillbirth and live born controls.
Result The Stockholm stillbirth database contains information on 1, stillbirths delivered between and Download: PPT. Table 1. Maternal characteristics, term live born and stillborn infants to normal weight and obese women. Table 2.
Placental and umbilical cord variables and birthweight; live born and stillborn infants to normal weight and obese women. Table 3. Primary cause of term stillbirth; lean and obese women. Table 4. Logistic regression models for the risk of stillbirth associated with obesity. Discussion In the present study, umbilical cord abnormalities could explain approximately one fourth of the effect of obesity on the risk of stillbirth at term. Conclusion Umbilical cord abnormalities may account for approximately one fourth of the effect of obesity on the risk of stillbirth at term.
Acknowledgments We would like to thank Stockholm Stillbirth Group for a fantastic and assiduous work with collection and categorization of all cases of Stillbirth during very many years. References 1. Major risk factors for stillbirth in high-income countries: a systematic review and meta-analysis. Lancet London, England. Stillbirths: the way forward in high-income countries. Every child alive: The urgent need to end newborn deaths. Stillbirths: recall to action in high-income countries.
Stillbirth among foreign-born women in Sweden. European journal of public health. Maternal body mass index and the risk of fetal death, stillbirth, and infant death: a systematic review and meta-analysis.
Trends in adult body-mass index in countries from to a pooled analysis of population-based measurement studies with The hyperglycemia and adverse pregnancy outcome study: associations of GDM and obesity with pregnancy outcomes.
Diabetes Care. Woolner AM, Bhattacharya S. Obesity and stillbirth. BJOG: an international journal of obstetrics and gynaecology.
Increased fetal plasma and amniotic fluid erythropoietin concentrations: markers of intrauterine hypoxia. Maternal prepregnancy obesity and cause-specific stillbirth. The American journal of clinical nutrition.
American journal of perinatology. Pinar H, Carpenter M. Placenta and umbilical cord abnormalities seen with stillbirth. Clinical obstetrics and gynecology. This condition can cause the woman's kidneys and liver to fail. In rare cases, seizures, heart attack, and stroke can happen. Other risks include problems with the placenta and growth problems for the fetus. Gestational diabetes —High levels of glucose blood sugar during pregnancy increase the risk of having a very large baby.
This also increases the chance of cesarean birth. Women who have had gestational diabetes have a higher risk of diabetes mellitus in the future. So do their children. Obstructive sleep apnea —Sleep apnea is a condition in which a person stops breathing for short periods during sleep. During pregnancy, sleep apnea can cause fatigue and increase the risk of high blood pressure, preeclampsia, and heart and lung problems. Birth defects —Babies born to women who are obese have an increased risk of having birth defects, such as heart defects and neural tube defects NTDs.
Macrosomia —In this condition, the fetus is larger than normal. This can increase the risk of injury during birth. Macrosomia also increases the risk of cesarean birth. Infants born with too much body fat have a greater chance of being obese later in life. This means that the baby is delivered early for a medical reason.
Preterm babies are not as fully developed as babies who are born after 39 weeks of pregnancy. As a result, preterm babies have an increased risk of short-term and long-term health problems. Losing weight before you get pregnant is the best way to decrease the risk of problems caused by obesity. Losing even a small amount of weight can improve your overall health and pave the way for a healthier pregnancy. To lose weight, you need to use up more calories than you take in.
You can do this by getting regular exercise and eating healthy foods. Your obstetrician—gynecologist ob-gyn may refer you to a nutritionist to help you plan a healthy diet. Also, the MyPlate website from the U. Department of Agriculture has a special section for women who are pregnant or breastfeeding. Increasing your physical activity is important if you want to lose weight. Aim to be moderately active for example, biking, brisk walking, and general gardening for 60 minutes or vigorously active jogging, swimming laps, or doing heavy yard work for 30 minutes on most days of the week.
You do not have to do this amount all at once. For instance, you can exercise for 20 minutes three times a day. If you have tried to lose weight through diet changes and exercise and you still have a BMI of 30 or greater or a BMI of at least 27 with certain medical conditions, such as diabetes or heart disease, weight-loss medications may be suggested. These medications should not be taken if you are trying to get pregnant or are already pregnant.
Bariatric surgery may be an option for people who are very obese or who have major health problems caused by obesity. If you have weight loss surgery, you should delay getting pregnant for 12 to 24 months after surgery, when you will have the most rapid weight loss. If you have had fertility problems, they may resolve on their own as you rapidly lose the excess weight.
It is important to be aware of this because the increase in fertility can lead to an unplanned pregnancy. Some types of bariatric surgery may affect how the body absorbs medications taken by mouth, including birth control pills. You may need to switch to another form of birth control. Despite the risks, you can have a healthy pregnancy if you are obese.
It takes careful management of your weight, attention to diet and exercise, regular prenatal care to monitor for complications, and special considerations for your labor and delivery. Finding a balance between eating healthy foods and staying at a healthy weight is important for your health and your fetus's health.
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