Drug Trial Designs Suitable for Pregnant Women.
Trial Design	Advantages	Disadvantages
Staggered trial design — Conduct stand-alone phase 1 trials simultaneously with phase 3 trials in the general population.*	Trials will generate phase 1 outcome data in pregnant women; women in later stages of pregnancy can be enrolled before women in the first trimester.	Studies cannot begin until phase 2 trials in the general population are complete.
Embedded trial design — Embed phase 1 trials for pregnant women into late phase 2 or phase 3 trials.*	Researchers can provide pregnancy-specific data sooner than would be possible with stand-alone trials because the subgroup of pregnant women can be given priority in the analysis stage.	Studies are logistically challenging; the availability of data from the overall population can be delayed if pregnant women are enrolled at a slower rate than nonpregnant adults.
Opportunistic study design — Enroll women who become pregnant while taking a drug as part of their clinical care or as part of a study.	Investigators would already be familiar with the study protocol, since they would have participated in earlier research phases with nonpregnant women; start-up costs and monitoring requirements are lower than in other types of trials in pregnant women.	Enrollment is likely to be slower than in other types of trials in pregnant women.

^*The options are discussed in detail by Baylis and Halperin.⁴