Is well water safe to drink during pregnancy?

What does the evidence say about well water and nitrates during pregnancy?

1. Private wells show higher nitrate levels more often than public water supplies, and current research has not established a clear cause-and-effect relationship between nitrate in drinking water and adverse reproductive outcomes, though some individual studies have reported associations with miscarriage, growth restriction, and birth defects. 1
2. Young, bottle-fed infants one to three months old are the group most susceptible to nitrate-induced methemoglobinemia, and the standard drinking water limit of 10 mg per liter of nitrate-nitrogen was set to guard against it; skin can take on a pale, gray-blue tone once methemoglobin reaches roughly 3 to 15% of the total. 2
3. Private, domestic wells are not continuously monitored the way public water systems are, and national sampling data found nitrate levels above the safety limit in about 9% of private wells tested, compared with about 2% of public wells. 3
4. A new pregnancy or a new infant in the household is one of the specific triggers that should prompt private well testing, on top of a general baseline of testing at least once a year for bacteria and nitrates. 4
5. Historical case data on infant methemoglobinemia shows that nitrate levels above about 50 mg of nitrate-nitrogen per liter, five times the standard limit, were tied to the large majority of documented cases linked to contaminated water used for formula. 2

Is well water and nitrates safe in each trimester?

• First trimester. If you are on a private well and have not tested recently, early pregnancy is a reasonable time to do it, since nitrate testing is quick and inexpensive and gives you a baseline for the rest of pregnancy.
• Second trimester. Nitrate levels in a well can shift with rainfall, snowmelt, and nearby agricultural activity, so a test result from a few years ago may not reflect what is in your water right now.
• Third trimester. If you plan to mix infant formula with well water after delivery, this is the moment to confirm your results are current, since infants under three months are the group most at risk from high nitrate levels.