There is usually no mother-to-fetus transmission, so research is needed to find out if the virus crossed the placenta or if the placentas of the women in the study were damaged or abnormal.
Kwa kawaida hii haipitishwi kutoka kwa mama kwenda kwa kijusi kwa hivyo uchunguzi zaidi unahitajika kujua ikiwa virusi hivyo vilipitia kwenye kondo au ikiwa kondo ya wanawake kwenye utafiti ilikuwa imeharibiwa au isiyo ya kawaida.