The association between the multiple birth and breast cancer incidence: an update of a systematic review and meta-analysis from 1983 to 2022

Table 2 Subgroup analysis of the association between multiple pregnancy and maternal risk of breast cancer by combining cohort/ case-control studies from 1983 to 2022 based on type of birth and continents

Studies	Variables	Pooled Risk Ratio	% 95 Confidence Interval	Heterogeneity assessment between studies		Heterogeneity assessment between subgroup
Studies	Variables	Pooled Risk Ratio	% 95 Confidence Interval	I square	P value	Q test	P value
Cohort	Continents
	Europe America	0.98 1.27	0.87–1.11 0.86–1.88	45.65% 62.41%	0.18 0.10	0.70	0.40
	Type of Birth
	Twin Multiple	1.39 0.91	1.14–1.69 0.85–0.99	0.00% 12.88%	0.38 0.16	5.50	0.02
Case-control	Continents
	Europe America	0.89 1.03	0.79–0.92 0.89–1.18	59.51% 0.00%	0.04 0.79	4.85	0.03
	Type of Birth
	Twin Multiple	0.90 0.87	0.82–0.99 0.79–0.97	52.22% 0.00%	0.03 0.66	0.22	0.64

ISSN: 2049-3258