Pat Glass voted in favour of the Marriage (Same Sex Couples) Bill at its third reading in May 2013.
In February 2015 Pat Glass voted against allowing mitochondrial donation, which would allow women who carried mitochondrial diseases to give birth to children who would not inherit the disease. If allowed, mitochondrial donation would be regulated by the Human Fertilisation and Embryology Authority (HFEA) meaning that there would be ongoing assessment of the safety and efficacy of such procedures. An October 2014 briefing report by the HFEA, which had been investigating the issue for three years, stated that there was no evidence to show that mitochondrial donation was unsafe. However, some religious groups had said that such procedures should not be allowed. The majority of MPs voted in favour of allowing mitochondrial donation.