Estimated incidence and number of new cases with prenatal alcohol exposure and fetal alcohol spectrum disorders in Finland 1990-2025

This study estimates that while prenatal alcohol exposure and fetal alcohol spectrum disorder (FASD) incidence in Finland have declined from the 1990s to the 2020s due to public health interventions, exposure remains common and the burden of FASD substantial, highlighting the need for continued biomarker-based research and strengthened prevention efforts targeting pre-pregnancy recognition.

The Gist

The Big Picture: A Hidden "Alcohol Shadow"

Imagine Finland as a large garden. The researchers wanted to know how many seedlings (babies) in this garden have been exposed to a specific type of "fertilizer" that can stunt their growth: alcohol consumed by the mother before or during pregnancy. This exposure is called Prenatal Alcohol Exposure (PAE). When this exposure causes lasting changes to a child's brain and development, it is called Fetal Alcohol Spectrum Disorder (FASD).

The problem is that this "fertilizer" is invisible. Many mothers don't realize they are pregnant immediately, or they might not admit to drinking because they feel guilty or fear judgment. So, the researchers had to act like detectives, piecing together clues from different sources to estimate how many children are affected.

The Detective Work: How They Counted the Unseen

Since they couldn't just ask every pregnant woman (because many would lie or forget), the team built a mathematical "recipe" to estimate the numbers. They mixed several ingredients:

1. The "Self-Report" Ingredient: They looked at what women said they drank. However, they knew this was like looking at a reflection in a funhouse mirror—it often distorts the truth. After 2004, when Finland started telling women to drink zero alcohol during pregnancy, the self-reported numbers dropped sharply. The researchers realized this wasn't necessarily because women stopped drinking, but because they were afraid to admit it.
2. The "Biomarker" Ingredient: To get a truer picture, they looked at "chemical footprints" left in blood and urine tests (like finding a fingerprint at a crime scene). These tests don't lie. They showed that even when women said they didn't drink, the chemical evidence told a different story.
3. The "International Comparison" Ingredient: They looked at schools in other countries (like Sweden, Poland, and the US) where researchers actually went into classrooms and tested children directly. They used these real-world numbers to create a "multiplier" to guess what the numbers might be in Finland.

What the Numbers Tell Us

The study covered a long timeline, from 1990 to 2025. Here is what their "recipe" produced:

• The "Any Exposure" Drop: In the 1990s, the model suggests that a huge chunk of babies (about 75%) were exposed to some alcohol before their mothers even knew they were pregnant. By the 2020s, that number dropped to about 32%.
  • Analogy: Imagine a foggy morning in the 90s where almost every car was driving through a thick mist. By the 2020s, the fog has lifted significantly, but it's still there for about one-third of the cars.
• The "Heavy Exposure" Reality: The study focused heavily on "binge drinking" (drinking a lot in a short time), which is like a sudden, heavy storm that damages the most. In the 90s, about 9% of pregnancies involved this heavy exposure. By the 2020s, it dropped to about 6%.
  • Note: Even though 6% sounds small, in a country like Finland, that still means thousands of children every year.

The Two Models: Two Different Maps

The researchers used two different ways to draw their map of FASD cases:

1. The "Multiplier" Map: This map looks at how much women in the country binge-drink generally and applies a ratio found in other countries. It suggests that 5.6% to 6.8% of children born in Finland have FASD.
2. The "Ratio" Map: This map uses an older rule of thumb (1 out of every 13 exposed babies gets FASD). It suggests a slightly lower number, dropping from 6% down to 3% over the years.

Both maps agree on the trend: The numbers are going down, but they are still much higher than previously thought.

The "Guests" Arriving from Abroad

The study also looked at children moving into Finland from other countries.

• The "Adoption" Group: In the early 2000s, many children were adopted from Eastern Europe and South Africa. The researchers estimated that 50% of these adopted children might have FASD.
• The "Immigrant" Group: Children arriving with their parents from countries like Russia, Estonia, and Ukraine also contribute to the numbers, though at a lower rate.
• Analogy: Think of the total number of affected children in Finland as a bucket. Most of the water comes from babies born in Finland, but a small, steady stream of water comes in from these "guest" buckets arriving from other countries.

The Conclusion: A Clearer View, But Still a Big Problem

The main takeaway is that while Finland has made progress (the "fog" is lifting and the "storms" are less frequent), FASD is still a massive, hidden public health issue.

• Why the numbers dropped: Better awareness, fewer babies being born overall, and a shift in drinking habits.
• Why the problem remains: Alcohol use before a woman knows she is pregnant is still very common. Also, the "stigma" (the fear of being judged) means many women still hide their drinking, making it hard to get the exact count.

The researchers conclude that to fix this, we need better tools to detect alcohol exposure (like the chemical footprints) and more active searching in schools to find children who are struggling but haven't been diagnosed yet. They warn that even if we stop all drinking today, there is still a large population of adults and children living with the effects of past exposure who need support.

Technical Summary

Technical Summary: Estimated Incidence and Number of New Cases with Prenatal Alcohol Exposure and Fetal Alcohol Spectrum Disorders in Finland 1990-2025

Problem Statement
Fetal Alcohol Spectrum Disorders (FASD) represent the leading preventable cause of neurobehavioral disorders and intellectual disability, yet national incidence estimates for Finland remain limited and largely based on passive surveillance, which significantly underestimates the burden. Previous estimates, such as a 1980s expert assessment suggesting 600–3,000 annual cases, lack contemporary data validation. Furthermore, self-reported alcohol use during pregnancy is notoriously unreliable due to stigma, particularly following the 2004 national recommendation for complete abstinence. The study addresses the need to estimate the incidence of any prenatal alcohol exposure (PAE) and heavy PAE, and to model the annual number of children with FASD born in or immigrating to Finland between 1990 and 2025, accounting for the limitations of self-reporting and the absence of national active case ascertainment studies.

Methodology
The authors developed a mathematical modeling framework integrating heterogeneous data sources to estimate incidence trends. The approach distinguishes between "any PAE" and "heavy PAE" (binge drinking), acknowledging that early exposure (before pregnancy recognition) is particularly critical for developmental damage.

• Data Integration: The model synthesizes data from published Finnish and international studies on alcohol use in pregnancy, national population statistics (Statistics Finland), WHO Global Health Observatory data on heavy episodic drinking, and international in-school active case ascertainment studies on FASD prevalence.
• Handling Data Reliability: Recognizing that non-anonymous self-reports are unreliable post-2004, the model prioritizes biomarker-based estimates (e.g., PEth, EtG) and fully anonymous self-reports. When multiple sources diverged, greater weight was assigned to biomarker and anonymous data.
• Modeling PAE Incidence:
  • Any PAE ($P_a$): Estimated using self-reported data including exposure before pregnancy recognition (BrP).
  • Heavy PAE ($P_h$): Modeled by combining binge-drinking prevalence, delayed pregnancy recognition rates, biomarker data, and anonymous self-reports. A weighting factor was applied to give double weight to biomarker and anonymous data compared to non-anonymous reports.
• Modeling FASD Incidence: Two distinct models were employed to estimate FASD prevalence ($F$):
  1. The M Model (Multiplier Model): Links FASD prevalence to the prevalence of heavy episodic drinking ($A_h$) among women using a country-specific multiplier ($M$) derived from international in-school studies (Sweden, Poland, Croatia, Italy, UK, US, Canada). This multiplier was calculated using weighted averages based on diagnostic criteria (IOM 2016 > IOM 2005 > Canadian guidelines), study size, and completion rates.
  2. The L Model (Ratio Model): Based on the epidemiological ratio proposed by Lange et al., estimating FASD as 1/13th of any PAE incidence, adjusted for very late pregnancy recognition.
• Immigration and Adoption: The models incorporate estimates for children with FASD immigrating with parents (from high-prevalence countries like Russia, Estonia, Ukraine) and internationally adopted children (with specific prevalence assumptions for Eastern Europe, South Africa, and other regions).
• Constants: Assumptions were made regarding late pregnancy recognition (20% recognized after 6 weeks; 0.2% recognized after 20 weeks) based on international and regional data, as specific Finnish data was unavailable.

Key Results

• PAE Trends: Self-reported alcohol use during pregnancy declined significantly following the 2004 abstinence recommendation, dropping from 75% (uncertainty range 60–85%) in the 1990s to 32% (26–38%) in the early 2020s. However, heavy PAE estimates, which rely more heavily on biomarkers and anonymous data, showed a more modest decline from 9% (7–11%) in the 1990s to 6% (4–8%) in the early 2020s.
• FASD Incidence:
  • The M Model (multiplier-based) estimated FASD incidence ranging from 6.8% to 5.6% (using a conservative multiplier) between the early 1990s and 2020s, with peaks in the early 1990s, 2008–2010, and a slight increase during 2020–2021.
  • The L Model (ratio-based) showed a steeper decline, estimating FASD prevalence decreasing from 6% to 3% over the same period.
• Absolute Numbers: Despite declining trends, the study estimates that approximately 1,500 to 2,500 new children with FASD are born or arrive in Finland annually using conservative numbers.
• Immigration Impact: Immigrant children with FASD constitute a small minority (approx. 2%) of new cases. An estimated 2,679 children with FASD immigrated to Finland between 1990 and 2024, with roughly half being international adoptees and half arriving with parents.

Significance and Claims
The paper claims that PAE and FASD represent a substantial and likely under-recognized public health burden in Finland. The estimated incidence rates (5–7% for FASD, depending on the model) are remarkably high compared to previous estimates (e.g., 1.2%) and suggest that Finland's traditional pattern of heavy episodic drinking among women contributes to a higher risk profile than in comparable Nordic countries like Sweden.

The authors emphasize that while trends are decreasing, the burden remains significant due to:

1. Methodological Artifacts: The decline in self-reported PAE likely reflects increased underreporting due to stigma rather than a proportional drop in actual consumption.
2. Early Exposure: The persistence of binge drinking before pregnancy recognition continues to drive risk for early embryonic damage.
3. Demographic Shifts: Declining birth rates and increasing numbers of lifetime abstainers (due to religious or other reasons) contribute to the reduction in absolute numbers, but the prevalence within the remaining birth cohort remains high.

The study concludes that current estimates are conservative and that the true burden may be higher. It calls for further biomarker-based population studies (using meconium or maternal hair) and in-school active case ascertainment studies in Finland to refine these estimates and guide public health interventions, particularly those targeting alcohol use before pregnancy recognition.