SB 3.31.4

caturbhir dhātavaḥ sapta
 pañcabhiḥ kṣut-tṛḍ-udbhavaḥ
ṣaḍbhir jarāyuṇā vītaḥ
 kukṣau bhrāmyati dakṣiṇe
Synonyms: 
caturbhiḥ — within four months; dhātavaḥ — ingredients; sapta — seven; pañcabhiḥ — within five months; kṣut-tṛṭ — of hunger and thirst; udbhavaḥ — appearance; ṣaḍbhiḥ — within six months; jarāyuṇā — by the amnion; vītaḥ — enclosed; kukṣau — in the abdomen; bhrāmyati — moves; dakṣiṇe — on the right side.
Translation: 
Within four months from the date of conception, the seven essential ingredients of the body, namely chyle, blood, flesh, fat, bone, marrow and semen, come into existence. At the end of five months, hunger and thirst make themselves felt, and at the end of six months, the fetus, enclosed by the amnion, begins to move on the right side of the abdomen.
Purport: 

When the body of the child is completely formed at the end of six months, the child, if he is male, begins to move on the right side, and if female, she tries to move on the left side.