We note 4 important limitations of our explanatory study. We explored only 4 of the various online recruitment platforms that could be leveraged for participant recruitment. At the time when the study was conducted, Reddit identified 12,927,467 active users. Platforms such as Facebook or Twitter may have been able to be used because of their wider user base, with Facebook boasting 1,712,000,000 users and Twitter 313,000,000 users as of the second quarter in 2016. However, Facebook’s inability to identify pregnant and smoking women in its advertising options prevented its usage in this study. Although Twitter does allow users to produce ads much like Reddit, Twitter’s reach also depends on the sender’s popularity. That is, many Twitter users must first “follow” the advertiser in order to see the advertiser’s ads. Another limitation of the study is consistency across platforms. For mTurk and Qualtrics, sample size was relatively limited. As with all studies utilizing online recruitment methods, our study relied on self-reported information. This presents the possibility that not all responses are completely accurate. A third limitation is that the method in which we recruited through Reddit may have yielded inaccurate responses. The mentions of “pregnancy” and “smoking” in our ads may have primed potential participants. This also may have been the reason for the “hack” that we experienced toward the end of the advertising campaign. Next, we recognize that we could not verify smoking status via Web. Although we attempted to design our quality screens by asking about the number of cigarettes in a pack and their preferred brand, we realize this is not a proven method of verifying smoking status. This is usually not an issue faced during in-person recruitment. For most in-person studies, smoking verification methods such as urine cotinine tests are more reliable and can be performed in the setting of a clinic. Lastly, it is important to address the intrinsic differences in the platforms that could have led to variation. First, the methods to target pregnant smokers vary by platform such that some, such as Reddit, are based off of subscriptions and readership while others, such as mTurk, are based off of demographic probability. Therefore, platforms that allow for customization and targeting might lead to a higher percentage of eligible participants than platforms that do not allow for customization. Second, given that the method of incentivizing differs across platforms, users of one platform may be more willing to complete the survey than users of another platform. However, to ensure generalizability, we attempted to use each platform as a typical research would and therefore ensured that the incentive participants received in each platform was similar to those of past researchers in the same platform. Finally, although we do not find it to be a limitation, we note that the difference in methods between mTurk and the other platforms may raise concerns. Turk Prime’s specific ability to only administer HITs to specific mTurk workers based on their anonymous ID meant that mTurk was the only platform where identifying information would not be collected but researchers could still follow up to respondents. In contrast, the Reddit platform required contact information to use as a screener. Therefore, the addition of the screener for mTurk’s platform is more of an asset than a limitation to our study.