Should Pregnant People Be in Clinical Trials?

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"It's unethical to include pregnant people in drug trials."

This is the conventional view. Excluding them is meant to protect pregnant people and their fetuses from unknown risks.

But consider this:

90M+

US women have given birth

That's 71% of women aged 18-85.

94%

of pregnant people use medications

On average, 3-5 different drugs during pregnancy.

But only

0.8%

of drug trials include pregnant participants

Out of 44,160 trials from 2008-2023, only 362 enrolled pregnant people.

Bilinski & Emanuel, AJOG 2025

<10%

of medications have sufficient pregnancy safety data

Among drugs approved since 1980, the vast majority lack adequate evidence.

CDC

What happens without trials?

Three case studies show how exclusion leads to preventable harm—whether a drug is dangerous or beneficial.

Case Study: Thalidomide (1956-1962)

8,000

infants affected by birth defects

A sedative prescribed for morning sickness caused severe limb defects. No trial was conducted in pregnant women.

99.6%

could have been prevented

A trial with just 200 participants would have detected the problem before widespread use.

~33
affected in trial
→
7,967
cases prevented

Bilinski, Emanuel & Ciaranello, Annals of Internal Medicine 2025

Case Study: COVID-19 Vaccines (2020-2021)

Pregnant people were excluded from vaccine trials

Despite objections from researchers, initial COVID-19 vaccine RCTs did not include pregnant participants.

The CDC didn't recommend vaccination during pregnancy until

Aug 2021

8 months after vaccines were authorized. Uptake lagged during the deadly Delta wave.

An RCT could have prevented:

8%
of maternal deaths
1%
of all stillbirths

March–November 2021. That's 71 maternal deaths and 139 stillbirths.

Bilinski, Emanuel & Ciaranello, Annals of Internal Medicine 2025

Case Study: Dolutegravir (2018-2019)

A false alarm reduced uptake of a life-saving HIV drug

Observational data suggested a safety risk. WHO cautioned against use in women of childbearing age. Later studies proved concerns unfounded.

3,228

preventable deaths

An RCT would have resolved the safety question faster, preventing the uptake gap that cost lives.

Bilinski, Emanuel & Ciaranello, Annals of Internal Medicine 2025

The bottom line

Excluding pregnant people from trials doesn't protect them—it just prevents researchers from learning when they take medications anyway.

The health value of trials far exceeds their cost

$100M
cost of a trial
vs
$1-33B
in preventable harm

Across all three case studies, trial costs were dwarfed by health benefits.

A path forward

Three policy levers could close the evidence gap

FDA Guidance
ICH E21 draft encourages pregnancy planning—make it binding
Pediatric Research Equity Act
Require pregnancy data like we require pediatric data
Best Pharmaceuticals for Children Act
Offer exclusivity incentives for pregnancy studies

It's time to include pregnant participants in clinical trials by default.

Read the research:

JAMA: Why This Is Unethical Annals: Health Impact Model AJOG: Trial Exclusion Data One-Pager
STAT: The case for including pregnant women in RCTs STAT: Acetaminophen use in pregnancy

Research by Dr. Alyssa Bilinski (Brown University), Dr. Natalia Emanuel (Federal Reserve Bank of NY), and Dr. Andrea Ciaranello (MGH/Harvard)