We thank Dr Sathiyathasan for his interest in our article on preventing recurrent miscarriage of unknown aetiology. The aim of the article is to summarise the current management of recurrent miscarriage of unknown aetiology rather than to give an update on current understanding of recurrent miscarriage. We therefore did not cover the relationship between endometriosis and pregnancy outcomes.
Debate on an association between endometriosis and recurrent miscarriage or spontaneous miscarriage has been ongoing for years.[1, 2] However, there is no strong evidence supporting this link or the link between the extent of endometriosis and the pregnancy outcomes in patients who underwent in vitro fertilisation (IVF) treatment.[2-6]
Omland et al. demonstrated that women with minimal endometriosis (n = 212) had similar pregnancy outcomes to women with tubal factor (n = 540) who underwent IVF/intra-cytoplasmic sperm injection (ICSI) cycles. Bahceci et al. were unable to demonstrate that women with endometriosis had higher miscarriage rates than women with the other underlying infertility aetiology on 1244 singleton pregnancies resulting from IVF/ICSI treatment. Likewise, Mohamed et al. also came up with a similar conclusion after retrospectively analysing nearly 4000 consecutive IVF cycles. Furthermore, Vercellini et al. indicated that there was no increase in spontaneous miscarriage in women with endometriosis (n = 419) who conceived naturally.
A large Danish population study (a total of 24 691 mothers and 12 389 daughters) found that daughters of women with endometriosis showed a two-fold increase in developing endometriosis compared with the daughters of women without endometriosis; however, their pregnancy outcomes were not dissimilar. Regarding adenomyosis, Mijatovic et al. demonstrated that adenomyosis does not pose any adverse pregnancy outcomes in women undergoing IVF/ICSI treatment.
I would agree with the reader that both immunological factors and/or oxidative stress from endometriosis may affect female fertility or embryo implantation.[1, 10] Nevertheless, the evidence of a possible link between endometriosis and recurrent miscarriage is currently lacking. Furthermore, treatment of endometriosis does not alter the pregnancy outcomes. Therefore, we concluded that endometriosis as a cause of recurrent miscarriage remains speculative.