Simantonnayana (Sanskrit: सीमन्तोन्नयन, Sīmantonnayana) (literally: parting the hair) is the third of the 16 saṃskāras (sacraments) practiced by the Hindus in which hairs of a pregnant woman are ceremoniously parted. According to the Grhya Sutras, the proper time to perform this saṃskāra is the fourth or fifth month of pregnancy but according to the smrtis and the astrological works, the period can be extended up to the eighth month or even birth of the child. The authorities are not unanimous whether this saṃskāra should be performed at each pregnancy or it should be performed only during the first conception. According to Ashvalayana, Baudhayana, Apastamba, Paraskara, Harita and Devala it should be performed only once. But other authorities think that it should performed during every pregnancy.
According to the Paraskara Gryha Sutra, at the beginning of the ceremony, the pregnant wife seats on a soft chair and with caressing attention, the husband himself parts her hairs upwards from the forehead three times, first with a bunch containing an even number of unripe udumbara (Ficus racemosa) fruits and three bunches of darbha grass, next with a porcupines quill having three white spots and finally with a stick of the Viratara wood and a full spindle, chanting each time three Mahavyahrtis (great mystical mantras), Bhur, Bhuvah and Svah. But according to Baudhayana different two verses are chanted.
According to Paraskara (I.15.6), after the partition of the hair, the husband ties the udumbara branch round her neck with a string of three twisted threads with the words, "Ayaṃūrjjāvato vrikṣaḥ urjjīva phalinī bhava" (Rich in sap is this tree; like the tree rich in sap, you be fruitful). But according to Baudhayana barley-sprouts instead of udumbara branch are used.
- Pandey, R.B. (1962, reprint 2003). The Hindu Sacraments (Saṁskāra) in S. Radhakrishnan (ed.) The Cultural Heritage of India, Vol.II, Kolkata:The Ramakrishna Mission Institute of Culture, ISBN 81-85843-03-1, pp.390-413
- Pandey, Rajbali (1969, reprint 2002). Hindu Saṁskāras: Socio-Religious Study of the Hindu Sacraments, Delhi: Motilal Banarsidass, ISBN 81-208-0434-1, pp.64-9