In the first batch of Pfizer documents released, the volunteer group I am part of was assigned to review Document 5.3.6, “Cumulative Analysis of Post-Authorization Adverse Event Reports.” Because a significant number of adverse events involving pregnant women were reported, I decided to pay particularly close attention to subsequent documents concerning the vaccine’s effects on pregnancy.

According to Pfizer’s Clinical Protocol, women who were pregnant or breastfeeding were excluded from participating in the vaccine trials.

Exclusion Criteria

On page 42, the protocol states:

11. Women who are pregnant or breastfeeding.

The protocol also addressed participants who became pregnant during the study. These women were to stop receiving further doses of the study intervention.

Under Section 8.2.6, “Pregnancy Testing,” on page 65, the protocol states:

“Pregnancy tests may be urine or serum tests but must have a sensitivity of at least 25 mIU/mL. Pregnancy tests will be performed in WOCBP at the times listed in the SoA, immediately before the administration of each vaccine dose. A negative pregnancy test result will be required prior to the participant’s receiving the study intervention.”

It further explains:

“In the case of a positive confirmed pregnancy, the participant will be withdrawn from administration of study intervention but may remain in the study.”

Pregnancies Reported During the Clinical Trials

The 2.5 Clinical Overview Document, on pages 320–321, provides additional information about pregnancies reported during the trials.

Under Section 2.5.5.7.2, “Pregnancies,” the document states:

“At the time of the data cutoff date (13 March 2021), a total of 50 participants who had received BNT162b2 had reported pregnancies, including 42 participants originally randomized to the BNT162b2 group and 8 participants originally randomized to the placebo group who then received BNT162b2.”

The document then describes participants who withdrew from particular vaccination periods because of pregnancy:

“In total, 12 participants (n=6 each in the randomized BNT162b2 and placebo groups) withdrew from the blinded placebo-controlled vaccination period of the study due to pregnancy, and 4 participants originally randomized to placebo who then received BNT162b2 withdrew from the open-label vaccination period due to pregnancy (Table 54).”

Importantly, the document says these participants continued to be followed for pregnancy outcomes:

“These participants continue to be followed for pregnancy outcomes. No births have been reported from individuals who have become pregnant in Study C4591001 as of the time of this submission.”

As I read the document, 16 participants withdrew from a vaccination period because of pregnancy. The wording is important here. It does not necessarily mean that all 16 withdrew completely from the study. Pfizer specifically states that the participants continued to be followed for pregnancy outcomes.

Follow-Up Requirements

The Clinical Protocol also describes how long participants were to be followed. Under Section 4.4, “End of Study Definition,” it states:

“A participant is considered to have completed the study if he/she has completed all phases of the study, including the last visit.”

It further notes:

“Participants enrolled in Phase 1 in groups that do not proceed to Phase 2/3 may be followed for fewer than 24 months (but no less than 6 months after the last vaccination).”

The protocol defines the end of the study as:

“The date of the last visit of the last participant in the study.”

What Happened to the 50 Pregnancies?

Using Abstractor, a front-end search tool for the released Pfizer documents, I searched the terms “pregnant” and “pregnancy.” In that search, I did not find updated information identifying the eventual pregnancy outcomes for these 50 participants.

That leaves an important question: What were the outcomes of these pregnancies?

Given the continuing debate and research surrounding mRNA COVID-19 vaccination during pregnancy, I believe the follow-up data on these 50 participants deserves careful examination. The Clinical Overview explicitly states that they were being followed for pregnancy outcomes. If those outcomes were subsequently documented, understanding where and how they were reported would help provide a more complete picture of what happened to these women and their pregnancies.