Ikut scan @ period (tapi takde period sbb tk prnh period lps lahir anak prtama

Salam sy nk tnye, ada tak ibu2 yg sama ngn sy. Xprnh period slps lahir prtama , pastu lekat ke2.. kita kena ikut scan kan. Tapi stiap kli scan EDD Brubah. Khmis scan 28 weeks, isnin scan dah 30 weeks (beza 4hari scan) Jd kite kena sllu ikut scan yg latest ke? Dkt buku pink nurse tulis USOP (unsure of period) Tq ibu2