The nation's leading group of obstetrician-gynecologists has asked the federal government to expand Medicaid to pregnant women and their children who were exposed to contaminated water in Flint, Mich.

The Centers for Medicare and Medicaid Services should provide Medicaid coverage to women who were served by the Flint water system from April 2014 to the point at which they become pregnant, the American Congress of Obstetricians and Gynecologists wrote to the agency on Friday.

The lead-contaminated water is especially dangerous for pregnant women because elevated lead in their blood increases risk to the fetus and can cause neurological problems in newborns. Elevated lead can also make it dangerous for women to breastfeed, ACOG wrote.

"Elevated lead levels in pregnancy have been associated with several adverse outcomes, including gestational hypertension, spontaneous abortion, low birth weight, and impaired neurodevelopment ... it is imperative that pregnant women who have been exposed to lead prior to pregnancy, not just during pregnancy, are able to access health care," the group wrote to CMS.

Michigan Gov. Rick Snyder has already made a similar request to the federal government, asking it to expand Medicaid coverage for all pregnant women and those under 21 who were exposed to the Flint water system, not just those currently eligible for the program due to income requirements.

News of lead contamination in Flint's water supply was recently made public, when authorities reported that for 18 months a lack of corrosion control in the river water caused lead to leak from old plumbing throughout the city. The crisis has put Snyder under a firestorm of criticism, since it was he who approved a plan for the city to get its water from the river instead of Detroit.

ACOG also asked the federal government to go beyond Snyder's request and continue providing Medicaid services to pregnant women and their children beyond the point in time that the Flint water system is deemed safe.

"A woman's prior exposure to lead can have long-lasting effects because lead can remain in bone tissue and be released when a woman is pregnant or lactating. Based on this physiologic reality, once the water system has been deemed safe, Michigan should continue to provide Medicaid services to this population," the group wrote.