Astanga Hrudaya
अव्यक्तः प्रथमे मासि सप्ताहात्कललीभवेत्। गर्भः पुंसवनान्यत्र पूर्वं व्यक्तेः प्रयोजयेत्॥३७॥
In the first month, during the first seven days, the embryo becomes a kalala (jelly mass) is unmanifest (undetermined in sex); hence pumsavana (methods to beget a male offspring) should be done before manifestation (differentiation of sex),
english translation
avyaktaH prathame mAsi saptAhAtkalalIbhavet। garbhaH puMsavanAnyatra pUrvaM vyakteH prayojayet॥37॥
hk transliteration by Sanscript