Table 2.

A co-occurrence analysis of theme-related words in the study titles

Co-occurring Themes	Frequency
(‘maternal’, ‘singing’)	4
(‘physiological’, ‘responses’)	4
(‘during’, ‘singing’)	3
(‘during’, ‘pain’)	3
(‘during’, ‘maternal’)	2
(‘maternal’, ‘recorded’)	2
(‘live’, ‘recorded’)	2
(‘live’, ‘physiological’)	2
(‘singing’, ‘therapy’)	2
(‘physiological’, ‘recorded’)	1
(‘recorded’, ‘responses’)	1
(‘live’, ‘responses’)	1
(‘recorded’, ‘therapy’)	1
(‘recorded’, ‘singing’)	1
(‘maternal’, ‘therapy’)	1
(‘during’, ‘physiological’)	1
(‘pain’, ‘physiological’)	1
(‘during’, ‘therapy’)	1
(‘during’, ‘live’)	1
(‘live’, ‘therapy’)	1
(‘live’, ‘singing’)	1
(‘during’, ‘mothers’)	1
(‘mothers’, ‘pain’)	1
(‘mothers’, ‘physiological’)	1
(‘live’, ‘mothers’)	1
(‘maternal’, ‘responses’)	1
(‘responses’, ‘singing’)	1