The short version: Most US tap water is safe to drink during pregnancy. But several common water contaminants — lead, PFAS, nitrates, and disinfection byproducts — have peer-reviewed research linking them to adverse pregnancy outcomes at levels that can occur in ordinary tap water. Whether you need to take action depends on what’s in your specific water supply.
When I was researching water quality for my family, I noticed something: almost every article about water and pregnancy either downplays the issue (“don’t worry, it’s all regulated”) or catastrophizes it (“your tap water is poisoning your baby”). Neither is helpful.
So I did what I always do — I pulled the actual studies. What I found is more nuanced than either extreme: there are real, documented risks from specific contaminants at specific levels, and you can check whether your water has them. Here’s everything I found, with every study cited so you can verify it yourself.
Why Pregnancy Changes the Equation
Water contaminants that might pose minimal risk to a healthy adult can be more significant during pregnancy for specific physiological reasons:
- Placental transfer is real. Many contaminants cross the placenta directly. A 2004 study by Gulson et al. in Environmental Health Perspectives confirmed identical lead isotopic ratios in maternal and cord blood, proving direct transfer to the fetus.
- Bone lead remobilizes. That same study documented a 10–50% increase in maternal blood lead levels during the third trimester — not from new exposure, but from lead stored in bones being released as the body mobilizes calcium for fetal development.
- Fetal organs are forming. The brain, kidneys, and endocrine system are actively developing. Contaminants that interfere with these processes have a disproportionate impact during narrow developmental windows.
- Blood volume increases ~50%. Pregnant women process significantly more water daily, increasing cumulative contaminant exposure.
None of this means tap water is dangerous during pregnancy. It means that for certain contaminants, the margin of safety is narrower than it is for non-pregnant adults.
The Six Contaminants That Matter Most
Not every contaminant in a water quality report is equally relevant to pregnancy. Based on the research, these are the six with the strongest evidence of pregnancy-specific risk.
1. Lead
The CDC, the AAP, and ACOG all agree: there is no safe level of lead exposure during pregnancy. The EPA’s action level is 15 parts per billion (ppb), but the health goal (MCLG) is zero. The CDC lowered its Blood Lead Reference Value to 3.5 µg/dL in 2021, meaning any level at or above that warrants intervention.
Edwards (2014) in Environmental Science & Technology studied Washington DC’s drinking water lead crisis (2000–2004). Fetal death rates peaked when water lead levels were highest and dropped after public health interventions. The correlation between DC fetal death rate and water lead level was strong (R² = 0.72), consistent with prior research linking lead exposure to miscarriage even at blood lead levels once considered “relatively low” (~5 µg/dL).
The critical nuance: lead in tap water almost always comes from your pipes, not the water source. Homes built before 1986 may have lead solder, lead service lines, or brass fixtures that leach lead. Your city’s water can test perfectly clean at the treatment plant and pick up lead on the way to your faucet.
2. PFAS (Forever Chemicals)
PFAS are synthetic chemicals that don’t break down in the environment or in your body. The EPA finalized its first-ever drinking water limits for PFAS in April 2024: 4 parts per trillion (ppt) for PFOA and PFOS, with a health goal of zero. The EPA explicitly noted that PFAS are transmitted to the fetus via the placenta.
Gao et al. (2021) conducted a systematic review and meta-analysis of 29 studies covering 32,905 participants in Environmental Research. Key findings: PFOS exposure was linearly associated with increased preterm birth risk. PFDA exposure was linked to significantly higher miscarriage risk (OR 1.87, 95% CI: 1.15–3.03). PFOS was also associated with increased preeclampsia risk (OR 1.27, 95% CI: 1.06–1.51).
PFAS contamination varies dramatically by location. Some communities have levels well above the new 4 ppt standard, while others have little to none. Checking your local water is the only way to know.
3. Nitrates
The EPA’s maximum contaminant level for nitrates is 10 mg/L, set specifically to prevent infant methemoglobinemia (“blue baby syndrome”). But research suggests pregnancy risks may begin at lower levels.
Lin et al. (2023) published a systematic review and meta-analysis in Scientific Reports covering over 5 million participants. Nitrate in drinking water was associated with increased preterm birth risk (OR 1.05 comparing highest vs. lowest exposure groups). For neural tube defects, the pooled odds ratio was 1.51 across three studies.
Croen, Todoroff & Shaw (2001) in the American Journal of Epidemiology found that exposure to nitrates above the EPA limit was associated with an OR of 4.0 for anencephaly (a fatal neural tube defect). Elevated risks appeared even below the MCL among groundwater drinkers.
Nitrate risk is highest if you’re on private well water in an agricultural area. Public water utilities are required to test and notify if nitrates exceed the limit. Private well owners have no such requirement — you have to test yourself.
4. Disinfection Byproducts (THMs & HAAs)
Chlorine keeps our water safe from bacteria — that’s important and necessary. But when chlorine reacts with natural organic matter in water, it creates byproducts called trihalomethanes (THMs) and haloacetic acids (HAAs). The EPA limits are 80 ppb for total THMs and 60 ppb for HAA5, based on lifetime adult exposure.
Waller, Swan et al. (1998) conducted a prospective study of 5,144 pregnant women published in Epidemiology. Women who drank 5+ glasses per day of cold tap water containing ≥75 µg/L total THMs had an odds ratio of 1.8 for spontaneous abortion. For bromodichloromethane specifically, the adjusted OR was 3.0 (95% CI: 1.4–6.6).
Important context: not all tap water has high THM levels. This depends on your utility’s source water and treatment methods. Your annual Consumer Confidence Report (CCR) lists your local THM levels.
5. Arsenic
The EPA’s limit for arsenic is 10 ppb, set primarily based on cancer risk. But pregnancy-specific research suggests risk may begin below that threshold.
Andrews et al. (2022) in Toxics studied 1,597 pregnant women and found that drinking water arsenic ≥2.5 ppb was associated with an odds ratio of 1.90 for miscarriage (95% CI: 1.07–3.38). That threshold is below both the WHO and EPA limits of 10 ppb.
Arsenic in drinking water is most common in certain regions with natural geological deposits, particularly parts of the Southwest, New England, and the upper Midwest. Well water users are at higher risk.
6. Hexavalent Chromium (Chromium-6)
The federal MCL covers total chromium at 100 ppb. California is the only state with a specific hexavalent chromium standard: 10 ppb, effective October 2024. There is no federal standard specifically for chromium-6.
Remy, Byers & Clay (2017) in Environmental Health analyzed 31 years of hospital data from a community exposed to chromium-6 in Willits, CA. Pregnant women in the exposed community had significantly higher pregnancy loss rates compared to controls. Birth defect rates and perinatal jaundice were also elevated and improved after the exposure source was closed.
Quick Reference: EPA Limits vs. Pregnancy Research
What Do the Medical Guidelines Say?
ACOG (American College of Obstetricians and Gynecologists)
ACOG Committee Opinion No. 832 (July 2021) identifies lead and mercury as “proven neurodevelopmental hazards” and states that obstetricians should become knowledgeable about “toxic environmental exposures that are endemic to their specific geographic areas, such as local water safety advisories (e.g., lead-contaminated water).” ACOG recommends screening patients for environmental exposures during prenatal care.
CDC
The CDC lowered its Blood Lead Reference Value from 5.0 to 3.5 µg/dL in October 2021, meaning any child — or fetus — with blood lead at or above that level warrants public health intervention. The CDC recommends that pregnant women avoid lead exposure and that physicians assess lead risk during prenatal visits.
EPA
The EPA’s 2024 PFAS rule explicitly notes that “pregnant women, lactating women, and infants may be more sensitive to harmful effects” of PFAS compounds. The EPA’s Maximum Contaminant Level Goals (MCLGs) for both lead and PFOA/PFOS are set at zero — acknowledging no known safe level of exposure.
How to Check Your Water
Here’s the practical part. Before you buy anything or change anything, find out what’s actually in your water.
Step 1: Use Our Free Water Quality Tool
I built a free water quality checker that pulls EPA data for your ZIP code and shows what contaminants have been detected in your local water supply. It takes 30 seconds and gives you a clear starting point.
Step 2: Read Your Consumer Confidence Report
Every municipal water system publishes an annual Consumer Confidence Report (CCR) listing every contaminant detected, the levels found, and whether they exceed EPA limits. Find yours through the EPA’s CCR search tool. Look specifically for lead, PFAS, nitrates, and THMs.
Step 3: Consider Testing at the Tap
Your CCR tells you what’s in the water at the treatment plant. It does not tell you what’s at your faucet — and that distinction matters for lead. If you have older plumbing (pre-1986), a lab test at the tap is the only way to know your actual lead exposure. Tap Score ($150–$200) is a certified at-home lab test that covers lead, nitrates, PFAS, and more.
What to Do If You Find Concerning Levels
If your water has elevated levels of any of the contaminants above — or if you simply want the precaution during the 9 months that matter most — here are your options by budget.
What does NOT work
Boiling does not remove lead, PFAS, nitrates, or THMs — it concentrates them. Standard Brita (white filter) does not remove PFAS, lead, nitrates, or fluoride. Fridge filters vary widely and most are only NSF 42 certified (taste and odor, not health contaminants). Always check for NSF/ANSI 53 or 58 certification.