Ariko ntabwo ari amagambo gusa cyangwa gushyushya inkuru gusa cyangwa ibitekerezo bidafite ishingiro kuko hari n’ubushakashatsi bubishyigikira.

Ubushakashatsi bwa siyansi bwakozwe ku buzima bw’ababyeyi bugaragaza ko koko hari itandukaniro rishobora kubaho hagati yo kubyara abahungu n’abakobwa, cyane cyane ku ngaruka bigira ku mubiri no ku gihe cyo kubaho.

Abashakashatsi batandukanye bakoze inyigo ku buzima bw’ababyeyi n’ingaruka z’abo babyaye (abahungu cyangwa abakobwa) ku buzima bwabo bwo kubaho igihe kirekire.

Nko muri Finland, hari ubushakashatsi bwamamaye cyane bwakozwe ku mibereho y’ababyeyi b’igitsina gore bwerekanye ikintu cyatangaje benshi, aho umubyeyi umubare w’abahungu yabyaye ushobora kugira uruhare ku gihe cye cyo kuramba nyuma yo kubyara.

Abashakashatsi basanze ko abagore babyaye abahungu benshi bagaragaje kugabanuka ku gihe cyabo cyo kuramba nyuma yo guhagarika kubyara, ugereranyije n’ababyaye abakobwa benshi. Ibi byatumye bamwe mu bahanga bavuga ko hari “igiciro” umubiri w’umugore wishyura bitewe n’igitsina cy’abana yabyaye, cyane cyane iyo ari abahungu benshi.

Impamvu zishobora kubitera, abahanga mu bijyanye n’ubuzima n’imiterere y’ibinyabuzima (biology) batanga ibisobanuro bitandukanye harimo ko abahungu basaba imbaraga nyinshi mu gihe cyo kuvuka no kubonsa, bigashyira umutwaro ku mubiri w’umubyeyi.

Ubushakashatsi bwakozwe na University of Helsinki, ku bijyanye n’ihindagurika ry’utunyangingo, bwagaragaje ko inda y’umuhungu ishobora kugira ingaruka zitandukanye ku mubiri w’umugore ugereranyije n’iy’umukobwa.

Ubundi bushakashatsi buherutse gukorwa nabwo bwerekanye ko umubare w’abana muri rusange ugira uruhare ku buzima bw’umubyeyi no kugena igihe cye cyo kubaho.

Ni ubushakashatsi bwakozwe na University of Helsinki, aho bwagaragaje ko abafite abana benshi cyane (barenga bane) bashobora gusaza vuba mu gihe abafite abana bake (2 cyangwa 3) bakunze kubaho igihe kirekire kurushaho. Ibi bishimangira igitekerezo cy’uko kubyara ari ingenzi mu buzima, ariko na byo bifite igipimo kidakwiye kurengwa.

Icyo abahanga bibutsa abantu, bavuga ko nubwo ubu bushakashatsi bwose bwerekana isano iri hagati yo kubyara (cyane cyane abahungu benshi) n’ubuzima bw’umubyeyi, bashimangira ko:
ibi ari ibigaragara ku rwego rusange (population level), atari ihame kuri buri muntu.

Hari n’ibindi byinshi bagiye bagaragaza bigira uruhare runini, harimo imirire, ubuvuzi
imibereho myiza ndetse n’uburyo ubuzima bw’umuryango muri rusange bwifashe.

Kandi hari ubushakashatsi bwerekana ko kuba umubyeyi ubwabyo bishobora no kongera igihe cyo kubaho ugereranyije n’utabyaye.