Abacwaningi baseMelika bafika esiphethweni sokuthi izingane ezazalwa ngaphambi kwesikhathi, kaningi kakhulu kamuva, zihlala zingenabantwana
Lesi siphetho sifike ngabososayensi baseMelika abathola isiphetho sabantu abayizigidi ezingu-1.2 abazalwa eNorway kusukela ngo-1967 kuya ku-1988. Ngokusho kwabacwaningi abavela kwi-Medical Center eDuke University, abantwana abangaba ngu-60 000 abazalwa ngalesi sikhathi bazalwa ngaphambi kwesikhathi. Kamuva abafana, abazalwa ngamasonto angu-28-32. babebababa abangamaphesenti angama-30 ngokuphindaphindiwe kunalowo owazalwa ngesikhathi. Lapho kuzalwa isikhathi esincane sokukhulelwa, ingozi yokungabi nabantwana yanda, uGeeta Swami, umholi wokufunda, waqaphela. Abafana abazalwa ngamasonto angu-22-27. ukukhulelwa, bathola inzalo yabo ngo-76% kancane kunelabo abazalwa emavikini angu 37-40. Amantombazane azalwe ngalolu suku abazange babe nabantwana abangama-67% kaningi kunelabo abazalwa ngesikhathi.