Critical appraisal of research methodology, strengths, and limitations

Prolonged use of oral contraception before a planned pregnancy is associated with a decreased risk of delayed conception.

Alexandra Farrow, M.G.R. Hull, K. Northstone, H. Taylor, W.C.L. Ford, and Jean Golding.

Publication Date: 2002

To determine whether or not prolonged use of oral contraceptives is associated with a greater difficulty in becoming pregnant or a delayed conception upon making the decision to become pregnant.

The sample consisted of 8497 planned pregnancies, or couples who were expecting the birth of a child. Participants were recruited over a 21-month period. The sample was drawn from an area in south-west England.

The study employed a prospective design in which participants completed questionnaires at 18 weeks of gestation. Questionnaires included details about parity, paternity, co-habitation, oral contraceptive use, smoking and alcohol status, educational achievement, height, weight and the amount of time it took for the couples to conceive.

Results:

The results of the study indicated that despite concerns about the impact of long-term use of oral contraceptives, the participants in this sample did not have a significantly prolonged period prior to conception. In fact, participants who had been on oral contraceptives reported a statistically significant reduction in the risk of delayed contraception.

Strengths & Weaknesses:

A potential limitation of the study was addressed through comparing the pregnant women with a sample of women who were not pregnant; to ensure that there was not a selection bias of any kind for fertile women. One remaining limitation however was that the study cannot be generalized to other forms of contraception, additionally, the study did not differentiate between types of oral contraceptives, so it could be that some have more harmful side effects for fertility than others.

Is previous use of hormonal contraception associated with a detrimental effect on subsequent fecundity?

Authors: M.A.M. Hassan & S.R. Killick

Publication Date: 2004

Purpose of Study:

To determine the effects of hormonal contraception on later fertility rates or the ability to get pregnant by choice after stopping the use of hormonal contraception.

Sample Details:

2841 women in Hull and Sheffield (UK) were asked to participate in the study.

Research Design:

The study used a questionnaire method, where women completed a number of questionnaires providing information on their use of contraceptives, their pregnancy planning process, their previous pregnancies, age, lifestyle characteristics of mother and father, as well as the amount of time it took to get pregnant.

Results:

The results of this study found that time to pregnancy was longer for women who had taken combined oral contraceptive for a long period of time, for those using short-term intrauterine devices (IUDs) and for women using any duration of injectable contraceptives. These hormonal contraceptives were compared to simply using a condom. Conversely, using only progesterone pills or an IUS was not associated with a delayed time to pregnancy.