When can a woman start combined hormonal contraceptives (CHCs)? A systematic review

Conventional methods of initiating combined hormonal contraceptives (CHCs), specifically combined oral contraceptives (COCs), the contraceptive patch and the contraceptive ring, require that women delay starting CHCs until menses begin, during which time a woman may be at risk of unintended pregnancy. The objective of this systematic review is to examine the evidence on the risk of becoming pregnant after starting the method (contraceptive effectiveness including surrogate measures such as ovarian follicular development and hormone levels), risk of already being pregnant, side effects and continuation when starting CHCs on different days of the menstrual cycle.

We searched the MEDLINE database for all articles (in all languages) published in peer-reviewed journals from inception through March 2012 for evidence relevant to starting CHCs on different days of the menstrual cycle and the outcomes of contraceptive effectiveness (including ovarian follicular development and hormonal levels), side effects and continuation rates.

From 1635 reviewed articles, 18 studies met our inclusion criteria. Evidence from four studies suggests that neither the risk of inadvertently starting COCs in a woman who is pregnant nor the risk of pregnancy after COC initiation are affected by the cycle day on which COCs are started. While follicular activity increased as the cycle day on which COCs were initiated increased, no women ovulated when starting on Day 5. When starting on Day 7, there was no increase in ovulation for a 30-mcg pill but a significant increase in ovulation with a 20-mcg pill compared with starting on Day 1. Evidence from two small studies suggests that 7 days of pills leads to inhibition of ovulation. One small study suggests that only 3 days of ring use is needed to inhibit ovulation, but this was following one complete treatment cycle of ring use. Evidence also suggests that starting CHCs on any day of the cycle does not affect bleeding problems or other side effects for both COCs and the patch. While starting CHCs via Quick Start (starting on the day of the health care visit) may initially increase continuation compared with more conventional starting strategies, evidence suggests that this difference disappears over time.

The body of evidence suggested that (a) pregnancy rates did not differ by the timing of CHC initiation; (b) the more follicular activity that occurred prior to starting COCs, the more likely ovulation was to occur; however, no ovulations were seen when COCs were started at a follicle diameter of 10 mm (mean cycle day=7.6) or when the ring was started at follicle diameter of 13 mm (median cycle day=11); (c) bleeding patterns and other side effects did not vary with the timing of CHC initiation and (d) continuation rates of CHCs were initially improved by Quick Start, but differences between groups disappeared over time.