Navigation Links
Babies born to native high-altitude mothers have decreased risk of low birth weight

BETHESDA, Md. (May 18, 2009) Pregnant women who are indigenous to the Andes Mountains deliver more blood and oxygen to their fetuses at high altitude than do women of European descent. The study helps explain why babies of Andean descent born at high altitude weigh more than European babies born at altitude.

The research, published in The American Journal of Physiology-Regulatory, Integrative and Comparative Physiology found that at high altitude:

  • the uterine artery of Andean women delivered more blood and oxygen to the fetus compared to women of European descent
  • the babies of Andean women weighed an average of nine ounces more at birth
  • the greater the mother's Andean heritage, the greater the uterine artery blood flow, the greater the oxygen delivery to the fetus and the greater the baby's birth weight

These differences between the Andean and European women and their babies did not exist at low altitude.

The question of why babies born at high altitude are smaller is not an academic one. Low birthweight is associated with higher rates of illness and mortality. By understanding this physiology, researchers hope to find out how to protect from reductions in fetal growth even in low-oxygen environments.

The study, "Augmented uterine artery blood flow and oxygen delivery protect Andeans from altitude-associated reductions in fetal growth." was done by Colleen Glyde Julian, Megan J. Wilson, Henry Yamashiro and Lorna G. Moore of the University of Colorado; Wilma Tellez, Armando Rodriguez and Enrique Vargas of Universidad Mayor de San Andrs, La Paz, Bolivia; Abigail Bigham and Mark Shriver of Pennsylvania State University; and Miriam Lopez of Clnica del Sur, La Paz, Bolivia. Dr. Yamashiro is also affiliated with Clinica Siran, Santa Cruz de la Sierra, Bolivia and Dr. Moore is also affiliated with Wake Forest University, Winston-Salem, North Carolina.

Birth weight differences

High-altitude pregnancies typically produce lower birth weight infants, even among women whose families have lived in high altitude for centuries. However, the babies of these women weigh more at birth compared to women whose ancestors have not lived at high altitude. European infants are three times more likely to be born small for their gestational age compared to Andean babies.

The same is true when comparing groups of women in other areas of the world, according to Dr. Julian, the study's lead author. Native Tibetan women's babies weigh more than the babies of Han women, a Chinese population that recently moved to the high altitude of Tibet. It is not clear what accounts for these differences, but they may occur because of differences in:

  • how much oxygen the mother is able to deliver through the uterine artery
  • how much nutrition and/or oxygen the mother is able to deliver through the placenta
  • a combination of both uterine artery and placental factors

Most likely, it is both the placenta and the uterine artery that accounts for these differences between Europeans and Andeans, Dr. Julian said.

More than 12,000 feet

The study took place in Bolivia and included two groups: pregnant women living at sea level and pregnant women living in the Andes Mountains (12,000 to14,000 feet). Each group included women of Andean and European ancestry. The researchers determined Andean ancestry through a combination of three methods: genetic testing, interviews and surnames.

The research focused on the uterine artery, which dilates to increase blood flow to the fetus during pregnancy. The low-oxygen environment at altitude affects the uterine artery, reducing blood flow and oxygen delivery to the infant. Reduced blood flow and oxygen slows fetal metabolism and results in slower growth.

The study predicted that this reduction in blood flow at altitude would be much less pronounced in the Andean women, who have adapted genetically to the high altitude. The researchers measured uterine artery blood flow by ultrasound at 20 weeks and 36 weeks of pregnancy, and three months post-partum. They also tracked fetal growth across pregnancy using ultrasound to measure fetal head and abdominal circumference, femur length and estimated fetal weight. The study found the following:

  • At sea level, the changes in uterine artery size during pregnancy were about the same for both the Andean and European women. There were no differences in fetal growth or birth weight between the two groups.
  • At high altitude, the uterine artery of both groups dilated less, reflecting the oxygen-poor environment.
  • Among the high-altitude group, the Andean women's blood flow was 68% greater at 20 weeks of pregnancy compared to the non-pregnant state, and the fetuses were larger at this stage. This suggests that the uterine artery is playing a causal role in the lower birth weight, as opposed to being a result of having a smaller baby and needing less oxygen or fewer nutrients, Dr. Julian said.
  • Among the high-altitude group, oxygen delivery to the fetus was nearly 2-fold greater in the Andean women at week 36.

The researchers also found a relationship at high altitude between the percent of indigenous Andean ancestry and the uterine artery blood flow, uterine oxygen delivery, and birth weight. In other words, the more Andean a woman was, the greater the uterine artery blood flow, the more nutrients delivered to the infant and the greater the birth weight.

This research may one day have implications for the development of therapeutic strategies to increase uterine artery blood flow or to change the way the blood vessels respond during pregnancies that are complicated by hypoxia and/or reduced fetal growth.


Contact: Christine Guilfoy
American Physiological Society

Related biology news :

1. If you want more babies, find a man with a deep voice
2. Evidence of a relationship between swimming babies and infections
3. Scientists find predisposition to bronchiolitis in some babies
4. Breathless babies: Preemies lung function shows prolonged impairment
5. Bacterial infections in premature babies more common than previously realized
6. Fewer babies born after Caesarean delivery
7. Exercise during pregnancy leads to a healthier heart in moms- and babies-to-be
8. Too much or too little weight gain poses risks to pregnant mothers, babies
9. Embryo biopsy does not affect early growth and risk of congenital malformations in PGD/PGS babies
10. Codeine not safe for all breastfeeding moms and their babies
11. Virus weaves itself into the DNA transferred from parents to babies
Post Your Comments:
Related Image:
Babies born to native high-altitude mothers have decreased risk of low birth weight
(Date:6/7/2016)...  Syngrafii Inc. and San Antonio Credit Union ... integrating Syngrafii,s patented LongPen™ eSignature "Wet" solution into ... result in greater convenience for SACU members and ... existing document workflow and compliance requirements. ... Highlights: ...
(Date:6/1/2016)... June 1, 2016 Favorable Government ... Administration and Criminal Identification to Boost Global Biometrics System ... released TechSci Research report, " Global Biometrics Market ... Forecast and Opportunities, 2011 - 2021", the global biometrics ... 2021, on account of growing security concerns across various ...
(Date:5/9/2016)... 9, 2016 Elevay is currently ... expanding freedom for high net worth professionals seeking travel ... globally connected world, there is still no substitute for ... duplicate sealing your deal with a firm handshake. This ... taking advantage of citizenship via investment programs like those ...
Breaking Biology News(10 mins):
(Date:6/27/2016)... Hill, N.C. (PRWEB) , ... June 27, 2016 ... ... U.S. commercial operations for Amgen, will join the faculty of the University ... serve as adjunct professor of strategy and entrepreneurship at UNC Kenan-Flagler, with a ...
(Date:6/24/2016)... ... June 24, 2016 , ... While the majority of commercial ... Cary 5000 and the 6000i models are higher end machines that use the more ... the spectrophotometer’s light beam from the bottom of the cuvette holder. , FireflySci ...
(Date:6/23/2016)... TORONTO , June 23, 2016 /PRNewswire/ - ... Ontario biotechnology company, Propellon ... the development and commercialization of a portfolio of ... cancers. Epigenetic targets such as WDR5 represent an ... contribute significantly in precision medicine for cancer patients. ...
(Date:6/23/2016)... NEW YORK , June, 23, 2016  The ... students to envision new ways to harness living systems ... of Modern Art (MoMA) in New York ... more than 130 participating students, showcased projects at MoMA,s ... included Paola Antonelli , MoMA,s senior curator of ...
Breaking Biology Technology: