Compare

Cervical Cap vs Diaphragm

A side-by-side comparison of two birth control methods — efficacy, cost, how they work, and who shouldn't use them.

Last verified October 11, 2026Updated October 11, 2026

Side-by-side comparison

Cervical Cap A small silicone cap that fits over the cervix by suction, used with spermicide before sex.
Diaphragm A reusable silicone dome that covers the cervix to block sperm, used with spermicide each time you have sex.

Method	Cervical Cap A small silicone cap that fits over the cervix by suction, used with spermicide before sex.	Diaphragm A reusable silicone dome that covers the cervix to block sperm, used with spermicide each time you have sex.
Efficacy	Cervical Cap 78% typical use Least effective: under 90 out of 100 people successfully prevent pregnancy per year.	Diaphragm 83% typical use Least effective: under 90 out of 100 people successfully prevent pregnancy per year.
Cost	Cervical Cap $0–$90 Insurance: Usually	Diaphragm $0–$250 Insurance: Usually
Duration	Cervical Cap Reusable for up to 2 years (replace sooner if worn or damaged)	Diaphragm Reusable for up to 2 years (replace sooner if damaged)
Reversibility	Cervical Cap Reversible	Diaphragm Reversible
STI protection	Cervical Cap No	Diaphragm No
How it works	Cervical Cap A small silicone cap fits snugly over the cervix and stays in place by suction, blocking sperm from entering the cervix. Used with spermicide inside the cap.	Diaphragm A reusable silicone dome covers the cervix to block sperm from reaching an egg. Used with spermicide for added effectiveness.
Prescription	Cervical Cap Required Hybrid (Fitting or Ship)	Diaphragm Required Hybrid (Fitting or Ship)
Side effects	Cervical Cap Vaginal irritation from spermicide Unusual vaginal discharge Toxic shock syndrome risk if worn during a period	Diaphragm Increased risk of urinary tract infection Vaginal irritation from spermicide Toxic shock syndrome risk (rare)
Who shouldn't use this	Cervical Cap Cervical anomaly preventing fit Active pelvic infection Sensitivity to silicone or spermicide Inability to insert or remove reliably History of toxic shock syndrome High risk of HIV exposure (because of the spermicide)	Diaphragm Uterine or cervical anomaly preventing fit Sensitivity to silicone or spermicide Inability to insert or remove reliably History of toxic shock syndrome High risk of HIV exposure (because of the spermicide)

Key differences

With typical use, 22 in 100 people using Cervical Cap get pregnant in a year, vs 17 in 100 with Diaphragm (both least effective). How long it lasts: Cervical Cap, reusable for up to 2 years (replace sooner if worn or damaged); Diaphragm, reusable for up to 2 years (replace sooner if damaged). Cervical Cap: costs $0–$90. Diaphragm: costs $0–$250.