When you're pregnant, you become acutely aware of everything you put into your body. The food, the medications, the cleaning products. But drinking water — which you consume eight or more cups of daily — often gets overlooked in that calculation. It shouldn't.
Pregnancy changes your physiology in ways that affect how your body processes certain contaminants. Blood volume increases by about 50%. Kidney filtration rate increases. Placental blood flow creates a new pathway between your bloodstream and your baby's developing systems. Some contaminants that your pre-pregnancy body could handle with no obvious ill effect can cross the placenta and affect fetal development during critical windows.
I'm not writing this to alarm you. The vast majority of pregnant women in the United States drink tap water and have healthy pregnancies. But I've seen the data on contaminated water supplies, and I know that the families most affected are often the ones with the least access to information and resources. This guide is about making sure you have the specific information you need to assess your own water situation — not a generic worry list, but actionable guidance.
Why Pregnancy Changes Your Water Safety Concerns
The developing fetus has very different vulnerabilities than you do as an adult. Several factors compound the risk of certain waterborne contaminants during pregnancy.
First, the fetal blood-brain barrier is not fully developed during early pregnancy. Contaminants like lead that can't easily enter an adult's brain can reach the developing fetal brain more readily, where they interfere with neurological development during critical periods.
Second, fetal organ systems — kidneys, liver, lungs, thyroid — are developing from scratch. Contaminants that affect hormone signaling or cellular development can disrupt these processes in ways that have lifelong consequences, even if the exposure was brief and occurred at levels that wouldn't significantly affect an adult.
Third, the placenta, while providing some protective function, is not an impermeable barrier. Lead, nitrates, some PFAS compounds, and several other waterborne contaminants cross the placenta. The concentration of these contaminants in fetal blood can reach levels similar to maternal blood levels.
Fourth, you're drinking substantially more water when pregnant — recommendations typically range from 10 to 12 cups per day in the third trimester, compared to 8 cups for non-pregnant adults. More water consumption means more exposure to whatever is in that water.
None of this means tap water is dangerous during pregnancy. It means that pregnancy is the right time to know specifically what's in your water and to take targeted protective steps if certain contaminants are present at elevated levels.
Lead: The Priority Concern During Pregnancy
Lead is the contaminant I'd worry about most if I were advising a pregnant woman about her drinking water, for several converging reasons.
Lead crosses the placenta readily. Studies consistently show that maternal blood lead levels and cord blood lead levels at birth are closely correlated. A pregnant woman with elevated blood lead — from any source, including water — exposes her fetus to similar levels.
The fetal nervous system is particularly vulnerable to lead during development. Even low blood lead levels in fetuses and infants are associated with reduced cognitive development, attention deficits, and behavioral problems. There is no established safe level of prenatal lead exposure.
During pregnancy, the body mobilizes calcium from bone stores to support fetal bone development. Lead is stored in bone alongside calcium, and when bone is mobilized during pregnancy, that stored lead can be released into the bloodstream — even from historical exposures that occurred years or decades earlier. This means a woman who had lead exposure as a child and has lead stored in her bones may have elevated blood lead during pregnancy from internal sources, completely separate from whatever is in her current water supply.
Practical steps for lead during pregnancy:
Get your tap water tested if you haven't already. A first-draw lead test from your kitchen faucet is the most relevant assessment. If results show lead above 5 ppb, install a certified NSF/ANSI 53 or 58 filter immediately and use it exclusively for drinking and cooking water.
Even with clean water test results, if your home was built before 1986, run your cold tap for 30 seconds each morning before using it for drinking. This flushes any water that sat in contact with plumbing overnight.
Ask your OB or midwife about blood lead testing. This is not universally offered but should be available, particularly if you live in a high-risk area (older home, area with known elevated water lead, proximity to industrial sites).
Nitrates During Pregnancy: The Blue Baby Connection
Nitrate is primarily discussed in the context of infant methemoglobinemia — the condition that affects formula-fed babies under six months. But nitrate is also a concern during pregnancy itself.
Nitrate is converted to nitrite in the body, and nitrite can cross the placenta. High nitrate exposure during pregnancy has been associated in some studies with adverse birth outcomes, including intrauterine growth restriction and preterm birth. A 2021 study in Environmental Health Perspectives found increased risk of preterm birth associated with elevated nitrate intake from drinking water in a large California cohort.
The evidence for pregnancy-related effects of nitrate at levels near the EPA limit (10 mg/L) is not as strong as the evidence for infant effects, but it's emerging and worth attention.
If you're in an agricultural area, farming community, or any area where nitrate violations have been recorded, check your CCR for nitrate levels specifically. If levels are above 5 mg/L — half the EPA limit — that's enough to warrant using a reverse osmosis filter for your drinking and cooking water during pregnancy.
After delivery, if you plan to breastfeed, this concern largely resolves — breast milk does not transmit nitrates to the infant the way formula prepared with nitrate-containing water does. The nitrate concern returns when you begin making formula, if formula feeding is part of your plan.
PFAS During Pregnancy: A Growing Body of Evidence
PFAS chemicals have become one of the more concerning water quality issues for pregnant women as research has accumulated. PFAS cross the placenta, and cord blood PFAS levels in newborns are closely associated with maternal blood levels. These compounds can also concentrate in breast milk, creating a second exposure pathway for newborns.
The health effects of prenatal PFAS exposure are an active area of research. Studies have found associations between maternal PFAS levels and reduced birth weight, altered thyroid function in both mothers and newborns, impaired immune development in infants (reflected in reduced antibody responses to vaccines), and preeclampsia.
The mechanism for several of these effects appears to involve PFAS interference with thyroid hormone signaling, which plays a critical role in fetal brain and organ development.
If your water system's Consumer Confidence Report or the EPA's UCMR5 database shows PFAS detected at any level — even below the new 2024 MCLs — pregnancy is a reasonable time to filter your drinking water. A reverse osmosis system is the most reliable approach for PFAS removal.
If you're already pregnant and concerned about past PFAS exposure, there's unfortunately little that can be done to remove existing body burden — PFAS are not easily excreted. This doesn't mean prenatal exposure is without consequence, but it does mean the focus should be on reducing ongoing exposure from water and other sources (PFAS-containing cookware, food packaging) rather than on any treatment or supplement that claims to remove PFAS from your body.
Disinfection Byproducts: The Shower and Swimming Pool Risk
Trihalomethanes (THMs) and haloacetic acids (HAA5s) — the disinfection byproducts formed when chlorine reacts with organic matter in water — have been studied specifically in relation to pregnancy outcomes, and the results are concerning enough to warrant attention.
Several large studies have found associations between TTHM levels in drinking water and adverse pregnancy outcomes including low birth weight, small for gestational age, and preterm birth. A 2018 meta-analysis found that exposure to high TTHM levels was associated with a 32% increased risk of small for gestational age births.
What makes the DBP pregnancy concern different from many other water quality issues is the route of exposure. While drinking water contributes to DBP exposure, showering and bathing can contribute substantially as well — particularly for volatile THMs, which evaporate from hot water and are absorbed through both skin and inhalation. Pregnant women who take long hot showers in highly chlorinated water may have meaningful dermal and inhalation exposure that adds to their dietary exposure.
Practical steps: check your CCR for TTHM and HAA5 levels. If TTHMs are above 50 µg/L or HAA5s above 40 µg/L, use a carbon block or RO filter for drinking and cooking water. Keep bathroom ventilation good during showers. Consider shorter, cooler showers if your water has high chlorine and TTHM levels — this is especially relevant in summer when DBP levels are highest. Some OBs recommend pregnant women avoid prolonged exposure to heavily chlorinated public pools during the first trimester specifically because of DBP concerns.
What to Actually Do: A Pregnancy Water Action Plan
Here is a practical action plan organized by what will make the most difference.
Step 1: Get your Consumer Confidence Report and check it. Look specifically for lead (90th percentile), TTHMs, HAA5s, nitrates, and any mention of PFAS. If you're in a high-arsenic region, check arsenic as well. This takes 20 minutes and gives you your actual water quality situation.
Step 2: Check WaterSafeCheck for your ZIP code. This gives you a quick summary of your water system's violation history, lead risk rating, and compliance score — useful context before you dive into the full CCR.
Step 3: Get a first-draw tap lead test. Especially if your home is pre-1986. Order a test kit online ($20–$35), follow the instructions for collecting a first-draw sample, and get results within a week or two. This is the single most actionable individual test for pregnancy water safety.
Step 4: Consider an under-sink reverse osmosis filter. If you're on a well, in a high-arsenic or high-nitrate area, have detected lead above 5 ppb, or have PFAS detected in your system — or honestly, if you're pregnant and want comprehensive protection without having to weigh individual contaminant levels — an under-sink RO system is the best single investment. It removes lead, nitrates, arsenic, PFAS, fluoride, and most other dissolved contaminants. Use it for all drinking and cooking water throughout your pregnancy.
Step 5: Talk to your OB. Ask whether blood lead testing is appropriate given your specific situation. Ask about any local water quality concerns they've heard about from other patients. OBs who practice in affected communities often have first-hand knowledge of local water issues that may not be fully captured in EPA databases.
Step 6: If you're on a private well, test now. Don't wait for your annual test. Get bacteria, nitrates, lead, and arsenic tested before your third trimester at the latest. If you discover a problem late in pregnancy, you still have time to get treatment in place or arrange for alternative water.
The Bottom Line
Pregnancy is a window of both vulnerability and opportunity. The months of pregnancy are when the food you eat, the air you breathe, and the water you drink have their greatest influence on a new person's development. That's not a reason for anxiety — it's a reason for knowledge.
Check your water. Get the CCR. Run a tap lead test if you're in an older home. Consider a reverse osmosis filter if multiple concerns are present or if you simply want peace of mind without having to evaluate each contaminant separately. Talk to your OB about local water quality issues.
The steps that protect your water during pregnancy are largely the same steps that will protect your family's water quality long after — so the investment you make now continues to pay off for years.
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Marcus J. Webb
Environmental Data Analyst, 10 Years EPA Compliance Research
Marcus spent a decade working as an EPA compliance analyst, tracking water quality violations and enforcement actions across hundreds of water systems in the Midwest and Mid-Atlantic. He built WaterSafeCheck to make EPA water quality data accessible to every American family — for free. He reads every reader email personally.
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