Satellite photo clearly shows fence which is on American soil with the border being located anywhere to a couple feet to a hundred feet or more north of the actual border.
The fence appears as a black line.
As in this photo of the border fence just west of Nogales
A pregnant Mexican could easily have her baby in the area marked on the map and in fact I think I see one house that actually straddles the border. The baby would be an American citizen with the only problem being able to prove the birth was in the USA. One way would be to have an open air birth with cameras rolling.
The baby is an American citizen can the American government keep the parents out?