Table 1.

Proposed sizes of the Arabin pessary for different clinical situations

Clinical situation & results from TVS	Proximal inner diameter		Distal outer diameter		Height
	32 mm	35 mm	65 mm	70 mm	17 mm	21 mm	25 mm	30 mm
Short cervix 2nd trimester
Singleton
No or Y-shaped funneling
Nulliparous	√		√			√
Parous	√			√		√
V- or U-shaped funneling
Nulliparous		√	√			√
Parous		√		√		√
Twins
No funneling
Nulliparous	√		√				√
Parous	√			√			√
V- or U-shaped funneling
Nulliparous		√	√				√
Parous		√		√			√
Short cervix (e.g. after cone biopsy) 1st trimester
Singleton
Nulliparous	√		√		√
Parous	√			√	√
Twins
Nulliparous	√		√			√
Parous	√			√		√
Additional signs of ‘prolapse’ in any patient
Nulliparous		√	√					√
Parous		√		√				√

Definition of ‘short cervix’ is relative and centile values specific for gestational age and different populations are preferred for definition of cut-off values. TVS, transvaginal sonography.