How many preterm births in England are due to excision of the cervical transformation zone? Nested case control study

Table 4 Estimated number of women referred and treated at colposcopy due to cervical intraepithelial neoplasia grade 2 (CIN2+) or worse diagnosis and the resulting excess preterm births each year in England

	N screening tests:	N referred to colposcopy:	N referred with mild	N referred with mod+	N with CIN2+:	Estimated excess number of future preterm births		Estimated excess number of future very preterm births
	N screening tests:	N referred to colposcopy:	N referred with mild	N referred with mod+	N with CIN2+:	per woman treated	in women treated	per woman treated	in women treated
20–24	46,050	4,668	2,852	1,816	2037	0.04	79	0.01	20
25–29	566,057	46,468	27535	18933	20844	0.03	630	0.01	149
30–34	497,109	24,640	16178	8462	10004	0.01	108	0.00	22
35–39	446,807	16,086	11036	5050	6216	0.00	23	0.00	6
total	1,556,023	91,861	57,600	34,261	39,101		840		196

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