I'm not sure this scans really because teenage births as well as teenage pregnancies enjoyed a local peak around 1990. There certainly was not a general pan-American societal instinct against teenage births at that time. The rate has fallen by more than 75% since. Even the mother-under-15 birth rate in 1990 was ridiculous (about 10x more than today, in most states).
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.
It's difficult to find teenage pregnancy rates before 1972, let alone multiple sources, but if you look at Guttmacher's numbers both teenage pregnancy and abortion rates ramped up significantly between the late 1970s and early 1990s. See https://www.guttmacher.org/sites/default/files/pdfs/pubs/UST... Teenage abortions rates are even more difficult to find before 1972, but abortion certainly existed in the 1950s, and given the birth rate it's possible teenage pregnancy rates were also higher in the 1950s and 60s.
Also, notwithstanding that the data does coincide with the given narrative, one must also consider socio-economic and cultural factors--pregnancy, birth, and abortion rates aren't homogenous across groups. For example, the OP (or their girlfriend) could have been from a segment of society at the trailing edge of a trend.
