Low vitamin A linked to small infant kidneys

By C. Vidyashankar, MD

DELHI (Reuters Health) - Mothers will low levels of vitamin A during pregnancy have an increased chance of giving birth to an infant with small kidneys, new research suggests.

The results of animal studies suggest a role for vitamin A, also known as "retinol," in the development of kidney structures called nephrons. Recent reports have also linked kidney size at birth with high blood pressure in later life. This prompted Dr. Paul Goodyer from the McGill University Health Centre in Montreal, and colleagues to compare the vitamin A status of pregnant women with the kidney size of their offspring at birth.

As reported in the journal Pediatric Nephrology, 48 women from Montreal and 46 from Bangalore, India with uncomplicated pregnancies were enrolled in the study. Nutritional status and blood retinol levels were assessed between 10 and14 weeks, 20 and 28 weeks, and 32 and 36 weeks. Kidney size in the newborns was determined within 2 days of birth using ultrasound.

The researchers found that retinol levels were lower in the Bangalore group compared with the Montreal group. At the same time, they found that the infants in Bangalore had smaller kidneys than their counterparts in Montreal.

Animal studies have shown that fetal kidney development depends on a chemical derived from vitamin A passed from the mother to the fetus, co-author Dr. Kishore Phadke, from St. John's Academy of Health Sciences, Bangalore, told Reuters Health.

"This concept could be extended to human kidney development," he said, "wherein maternal vitamin A levels will be crucial to determine the nephron number, size and function of kidneys in the developing fetus."

If the link between maternal vitamin A and fetal kidney size is confirmed by larger studies, "there may be important public health implications for regions of the world where maternal vitamin A deficiency is prevalent," the researchers conclude.

However, Phadke noted that vitamin A supplements are not routinely recommended for pregnant women in India, because of the narrow therapeutic dose range. "Excess vitamin A supplementation can cause (harmful effects) in the growing fetus and this makes universal supplementation of vitamin A difficult in pregnant women."

SOURCE: Pediatric Nephrology, February 2007.