Executive Summary: Key Legal and Evidentiary Issues

• Scope and sufficiency of the plaintiffs’ factual allegations about regular Tylenol (acetaminophen) use in pregnancy and resulting ASD/ADHD in their children at the authorization stage.
• Relevance and admissibility of evolving scientific studies on prenatal acetaminophen exposure, causation, and the weight to be given to genetic and familial risk factors for ASD/ADHD.
• Proper limits on pre-authorization discovery, including whether written interrogatories of representative plaintiffs are essential or amount to an impermissible pre-trial fishing expedition.
• Extent to which defendants may clarify plaintiffs’ product use (specific Tylenol products, quantity, and frequency) and family medical history without overreaching into merits-based defences.
• Application of Quebec procedural rules on amendments and proportionality, confirming that modifications to the authorization application are generally allowed when pertinent to article 575 C.p.c. criteria.
• Allocation of procedural rights without cost consequences, as both sides obtain part of their requested relief but no party receives any monetary award or costs in this interlocutory ruling.

Factual background and proposed class

This case arises from a proposed class action in the Superior Court of Québec (Class Actions Chamber) brought by representative plaintiffs Jade Corbeil and Merieme Hamzi against Johnson & Johnson and Kenvue Canada Inc. The application for authorization to institute a class action was originally filed on 20 October 2022; the original plaintiff, Ms. Chouinard, was later replaced by Ms. Corbeil and Ms. Hamzi by court order on 3 April 2024. The plaintiffs allege that regular use of Tylenol during pregnancy, whose main active ingredient is acetaminophen, causes the unborn child to develop either autism spectrum disorder (ASD) or attention deficit hyperactivity disorder (ADHD). They claim that prenatal exposure to Tylenol products materially increases the risk of such neurodevelopmental outcomes.
The proposed class is composed of all parents in Québec (including deceased parents and/or their estates) with a child whose biological mother regularly ingested, during pregnancy, Tylenol or other products of the defendants containing acetaminophen alone or in combination with other medications, as listed in the application. The child must subsequently have developed ASD or ADHD, and the parents and affected children are intended to fall within the scope of the “PRODUCTS” as defined in the pleading.

Allegations concerning product use and duty to warn

The plaintiffs’ case is grounded in product liability and failure-to-warn theories. They allege that the defendants marketed and sold a range of Tylenol-branded medications — nineteen different Tylenol products are referenced in the amended authorization application — without providing adequate warnings about the risks associated with regular acetaminophen use during pregnancy. The pleadings include allegations about the obligation to warn users, together with assertions about the defendants’ advertising and marketing campaigns that allegedly promoted Tylenol as safe during pregnancy.
In addition to the factual assertions about individual product use, the plaintiffs seek to rely on scientific literature regarding the relationship between prenatal acetaminophen exposure and later ASD/ADHD in children. They also refer to Health Canada’s position on acetaminophen use in pregnancy, as well as broader allegations about what the defendants knew or ought to have known and what they communicated, or failed to communicate, to consumers. These elements are intended to support the existence of a defensible cause of action and common issues under article 575 C.p.c.

Procedural posture and amendments to the authorization application

The judgment concerns two interlocutory issues at the pre-authorization stage: a motion to further amend the authorization application, and a defence motion seeking leave to examine the representative plaintiffs.
On 11 November 2025, the plaintiffs filed a new motion to amend their already amended application for authorization, followed by further additions on 4 December 2025. The amendments sought to introduce new allegations about the evolution of scientific studies on Tylenol use during pregnancy and its impact on unborn children, to describe Health Canada’s position on acetaminophen use in pregnancy, to expand the allegations regarding the duty to warn users, and to add several details concerning the plaintiffs’ personal situations. Additional documentary exhibits were proposed, including three new exhibits (P-17 to P-19) and an updated list of exhibits P-9 to P-19.
In class action proceedings in Québec, the court’s permission is always required to amend pleadings, but the general rule is that amendments should be allowed and refusal is exceptional. The court applies the general modification rules in articles 206–208 C.p.c., and the amendments must be relevant to the assessment of the authorization criteria under article 575 C.p.c. In this decision, the court concluded that the proposed amendments were pertinent to the authorization analysis, particularly because they refined the factual and scientific context of the alleged harm and clarified the personal circumstances of the representative plaintiffs. As a result, the court granted leave to amend and accepted the updated Amended 2 Application for Authorization to Institute a Class Action and to Appoint Representative Plaintiffs dated 4 December 2025, along with the new exhibits.

Request for leave to examine the representative plaintiffs

The defendants also brought a motion seeking leave to examine the representative plaintiffs before the authorization hearing. They sought oral examinations of Ms. Corbeil and Ms. Hamzi on several broad topics, including: their purchase and use of Tylenol products during pregnancy (covering quantity, product types, frequency, and whether Tylenol was used with other medications or treatments); their medical condition and reasons for using Tylenol; any medical advice received regarding Tylenol use during pregnancy; relevant familial medical history and other risk factors for ASD/ADHD; their children’s neurodevelopmental diagnoses; any inventory or communications with other putative class members; and the defendants’ advertising and marketing regarding Tylenol’s safety during pregnancy and plaintiffs’ reliance on such messaging. Each examination was estimated to last about two hours.
The plaintiffs opposed the motion, arguing that the court should be cautious about authorizing pre-authorization discovery. They asserted that, especially with the new amendments, the pleadings about their personal situations were sufficiently clear and precise for the authorization stage, and that broad examinations would amount to an impermissible pre-trial inquiry into the merits.

Legal framework governing pre-authorization examinations

The court relied on recent case law, including Jean-Antoine v. Samsung Electronics Canada Inc., to summarise the legal principles that govern requests to examine a proposed representative plaintiff before an authorization hearing in a class action. Under Québec practice, any such examination is permitted only if it is essential to assessing the criteria of article 575 C.p.c., and it must comply with the overarching principles of reasonable conduct and proportionality in articles 18 and 19 C.p.c. An examination that primarily serves as a pre-enquête or fishing expedition into the truth of the allegations or into the quality of the plaintiffs’ evidence should not be authorized, as those issues belong to the merits. The burden lies on the party seeking the examination to demonstrate its necessity and appropriateness in relation to the limited authorization test.
The court also noted that, under article 158(3) C.p.c., it has discretion to limit the scope of an examination and to determine the conditions under which it will proceed. This includes the ability to order written interrogatories instead of oral examinations where the topics are narrow or straightforward, thereby maintaining proportionality and efficiency.

Scope of written interrogatories permitted

Applying these principles, the court granted the defendants only a limited right to examine the representative plaintiffs, and it did so exclusively by written interrogatories. It considered that some focused clarifications might help the court assess whether the plaintiffs had presented a “defendable” cause of action at the authorization stage, particularly on issues of product use and potential causation.
The court therefore authorized written examinations on two narrow sets of topics. First, the plaintiffs may be questioned on their purchase and use of Tylenol products during their pregnancies, specifically: (i) the quantity of Tylenol products they consumed during pregnancy, (ii) the types of Tylenol products they used, and (iii) the frequency of their use. This information is especially pertinent because the amended application references nineteen distinct Tylenol products, and the pleadings describe “regular use” of Tylenol during pregnancy, a term the court considered capable of further clarification in terms of quantity, duration, and frequency. The court noted that no medical records could be located for Ms. Corbeil, making her examination the only way to obtain details of her Tylenol exposure. For Ms. Hamzi, the available medical notes suggested a prescription for Tylenol only a few days before delivery, raising questions that required clarification about the actual pattern of use.
Second, the court allowed questions on relevant familial medical history and risk factors related to ASD and ADHD. These elements did not appear in the medical files of the plaintiffs or their children, so interrogatories were again the only realistic way to obtain that information. The court considered family history to be a potentially relevant factor in the causal analysis between maternal Tylenol use and subsequent ASD/ADHD in the child: while one of the plaintiffs’ cited studies appeared to minimise the impact of genetic external factors, another study indicated that genetic and familial risk factors must be considered when evaluating causality. The court therefore treated familial history as a relevant aspect of the causation inquiry that would form part of assessing whether the case presents a defendable cause of action.

Limits imposed on defence discovery

The court refused to authorize interrogatories on the remaining topics sought by the defendants. Questions concerning whether Tylenol products were used in conjunction with other medications or treatments were found to go beyond the needs of the authorization stage and to verge on a broader pre-enquête into the plaintiffs’ medical history and potential alternative causation, which properly belongs to the merits.
Similarly, the court declined to permit questions on the plaintiffs’ medical conditions during pregnancy beyond what was already pleaded, finding that the allegations were sufficiently clear: Ms. Corbeil alleged sinus-related headaches, supported by a RAMQ document, and Ms. Hamzi alleged chronic migraines, which appeared in her medical file. These details, combined with the existing documentation, were considered adequate at the procedural stage. The court also held that any advice given by treating physicians about Tylenol use in pregnancy was not relevant to the authorization analysis.
The defendants also sought to question the plaintiffs on their children’s neurodevelopmental diagnoses and on advertising and marketing campaigns about the safety of Tylenol during pregnancy, as well as the plaintiffs’ reliance on such campaigns. The court rejected these as outside the necessary scope for authorization. It observed that both children’s diagnoses were well supported by documentation: Ms. Corbeil’s child has a confirmed autism diagnosis, and Ms. Hamzi’s child has a confirmed ADHD (TDA) diagnosis. As such, further questioning on this topic was unnecessary at the present stage. On the advertising and marketing side, the defendants argued there were evidentiary gaps, such as the absence of product labels or specific advertising materials; however, the plaintiffs maintained that these were matters of notoriety that did not require proof at authorization. The court treated these disputes as belonging to the upcoming authorization hearing, not to pre-authorization discovery, and declined to extend interrogatories to these contested issues.

Procedural directions and outcome of the motions

Exercising its discretion under article 158(3) C.p.c., the court ordered that the interrogatories proceed in writing and set precise procedural timelines. The defendants must transmit their written questions to the plaintiffs by 16 January 2026, in conformity with the framework in article 223 C.p.c., except that the plaintiffs are given three weeks from receipt, rather than the standard range, to answer. The questions must be clear and precise such that a failure to answer could be interpreted as an admission of the facts at issue.
Under article 224 C.p.c., the plaintiffs’ answers must be provided in writing, under oath, and signed, with direct, categorical, and precise responses; if the answers are inadequate, the facts they address may be deemed admitted. The court confirmed that the plaintiffs may respond by way of sworn declaration and that no further oral examination will take place based on that declaration. Both the written questions and answers must be filed in the court record, where they will form part of the evidentiary record available to the authorization judge.

Ruling, successful parties, and monetary consequences

In the result, the court granted the plaintiffs’ motion to further amend their authorization application and accepted the filing of the updated Amended 2 Application and the new exhibits. It also partially granted the defendants’ motion by authorizing only narrowly tailored written interrogatories on (i) the quantity, type, and frequency of Tylenol use during the pregnancies, and (ii) relevant familial medical history and risk factors for ASD/ADHD, while refusing broader pre-authorization discovery on medical conditions, diagnoses, other medications, class-member communications, and advertising and marketing issues. Both sides thus emerged partially successful: the plaintiffs obtained the full scope of their requested amendments, and the defendants secured limited but meaningful discovery on specific issues important to causation and exposure. However, the judgment expressly states that it is rendered “sans frais,” meaning that no costs are awarded to either party and no damages or other monetary relief are granted at this interlocutory stage; consequently, no determinable monetary amount was ordered in favor of any party in connection with this decision.