It is estimated that about 40% of pregnancies in the world are unintended and that the major part of these are unwanted. There are several reasons no or ineffective contraception is used to prevent these pregnancies, including difficulty in obtaining contraceptives. The lactational amenorrhoea method (LAM) is a contraceptive method where the mother is informed and supported in how to use breastfeeding for contraception. LAM is available and accessible to many women.
To assess the effectiveness of LAM, as defined in the 1988 Bellagio Consensus statement, as a contraceptive method in fully breastfeeding women, who remain amenorrheic, using pregnancy and menstruation life tables.
We searched MEDLINE, EMBASE, POPLINE, and LILACS to 10 October 2014; reference lists of studies; review articles; books related to LAM; published abstracts from breastfeeding, reproductive health conferences; e-mails with study coordinators.
Out of 459 potentially relevant studies, 159 investigated the risk of pregnancy during LAM or lactational amenorrhoea. Our inclusion criteria were as follows: prospective study; cases (intervention group) and, if available, controls, had to be sexually active; pregnancy had to be confirmed by physical examination or a pregnancy test. Our endpoints were life table menstruation rates and life table pregnancy rates. We included 15 studies reporting on 11 intervention groups and three control groups. We identified one additional uncontrolled study in the 2007 update and one additional controlled study in this 2015 update.
Two review authors independently extracted data, resolving disagreements through discussion. We analysed the studies using narrative methods because of their heterogeneity.
For the primary outcome, pregnancy, two controlled studies of LAM users reported life table pregnancy rates at six months of 0.45% and 2.45%, one controlled study reported 5% pregnancies in the absence of life table rates per month, and eight uncontrolled studies of LAM users reported pregnancy rates of 0% to 7.5%. Life table pregnancy rates for fully breastfeeding women who were amenorrheic but not using any contraceptive method were 0.88% in one study and 0.9% to 1.2% (95% confidence interval 0.0 to 2.4) in a second study, depending on the definition of menstruation used. The life table menstruation rate at six months in all studies varied between 11.1% and 39.4%.
We found no clear differences in life table pregnancy rates between women using LAM and being supported in doing so, and fully breastfeeding amenorrheic women not using any method. As the length of lactation amenorrhoea in women using LAM differed greatly between the populations studied, and was population specific, it is uncertain whether LAM extends lactational amenorrhoea.