Objective
To improve understanding of contraceptive use over 1 year among women in the United States.

Study design
We used the 2013–2015 National Survey of Family Growth to examine monthly contraceptive use patterns over a 12-month period. We focused on use of contraception during months in which non-sterilized women were sexually active and not pregnant; our outcomes were contraceptive use in every month, some months, and no months. We used simple and multivariate logistic regression to examine socio-demographic and method use characteristics associated with contraceptive use patterns.

Results
Some 72% of non-pregnant, non-surgically sterile women used contraception in every sexually active month. After controlling for other demographic and individual characteristics, adolescents had higher odds (aOR = 2.45) of using contraception in each sexually active month compared to women aged 25–29. Other groups more likely to use contraception monthly included those with some college (aOR = 1.58) compared to less than high school and non-cohabiting unmarried women (aOR = 1.49) compared to married women. Those with gaps in insurance coverage during the past year (aOR = 0.70), women who were not sexually active all 12 months (aOR = 0.42), and those with more than two male sexual partners (aOR = 0.49), were less likely to use contraception every sexually active month. Nearly half (46%) of contraceptive users in our sample used more than one type of contraceptive method over the 12-month period.

Conclusions
The majority of women use contraception every month they are sexually active, although there is variation between socio-demographic groups. However, over a one-year period, many women used dynamic contraceptive strategies.

Implications
Health care providers should recognize that contraceptive use patterns are dynamic and change over a relatively short time period for many women.