In our daily life, we come across the word Sarpa dosha. Let us examine what is Sarpa dosha? Sarpa is the race of Surasa, inhabiting the waters Bhogavati beneath the Earth. They are supposed to have human face serpent-like lower extremities their kings are Shesha, Vasuki and Takshaka. 7 or 8 of the Sarpas are particularly mentioned in Mahabharata.
Sarpa dosha and planetary dispositions:

Rahu occupying the eighth from lagna, identical with a malefic sign, in conjuction with or aspected by Sani, Rahu and Gulika in the eighth, Rahu occupying the badhaka Rasi in conjuction with Sani or aspected by Sani and Rahu and Gulika in the badhaka Rasis. If Rahu or Ketu is in the lagna, 2nd, 5th, 7th or 8th house, it is generally said to have Sarpa dosha. Ketu in the lagna called Manglya Sarpa Dosha causes delay in marriage. Ketu in the 2nd house called Aayurbhava Sarpa dosha creates longevity problems. Ketu in the 11th house called Putra bhava Sarpa dosha causes progency related problems. Rahu occupying the 8th from lagna, identical with a malefic sign, in conjuction with or aspected by Sani. Rahu and Gulika in the eighth, Rahu occupying the badhaka Rasi. 11th for moveable signs of Mesha, Karkataka, Tula and Makara, 9th house for fixed signs of Vrushaba, Simha, Dhannus and Kumba and 7th for dual signs Mithuna, Kanya, Dhannus and Meena Rasis.
It is widely believed that the childless couples will be blessed with a child, if they observe the Naga Panchami vratra. Those who read the story from the Mahabharata on the day of Nagapanchami after worshipping Sarpas will be greatly relieved from the problems due to Sarpa dosha. The impact of Sarpa dosha is so severe that it may create early curtailment of wedlock, by death of spouse or divorce, delay in progency or no progency and unexpected accidents.
Dosha Nivarana Mantra should be recited for 108 times daily for more results that are effective.

Sarpa Dosha Nivarana Mantra

'Anantho Vasukee Seshaha Padmanaabhascha Kambalaha
Sankhapaalo Dhaatharaastraha Takshaka Kaaliyasthatha
Ethaani Navanaamaani Nagaanaam cha
Saayamkaale pateth nityam praathakaal
Remedial Measures

Purchase two silver Sarpa prathimas five headed and two bodied idols and worship on Tuesday and Saturdays for 18 weeks. Visit the temple of Lord Subrmanya swamy every day and worship. Wear Gomed in a silver ring in the middle finger. Perform pooja of Lord Narasimha. Sri Krishna Himself sincerely worshipped Lord Narasimha that the poison of the evil snake Kaaliya had no effect on Him. Chant Lord Subramanya swamy ashtaka every day with utmost faith and sincerity. Visit Rameswaram, Devipattinam and the Navagraha temples around Kumbakonam with your spouse and offer prayers. Perform Garuda Panchami Vratra regularly every year. Donate pulses to the poor on 43 Wednesdays.