The local peak around 1990 was a very small bump from the flat run through the 1980s, and was probably a brief rebound effect of the extreme negative social pressure related to unprotected casual sex stemming from the AIDS crisis fading a bit as that became perceived as less acute of a threat, and there numbers dropped rapidly after that peak, quickly going through the floor they had settled in during the long flat period preceding the brief rise and peak.

So it is not at all inconsistent with a strong social force against teenage births existing and being acted on in the late 1990s, in fact, had that not existed the rise up to the 1990 peak would probably not have been so brief and followed by a rapid drop that went straight through the preceding floor.