Fertility drugs enhance the chances of conceiving by stimulating the ovaries to produce more eggs. However, more than one egg can be fertilized increasing the probability of multiple pregnancies.
Twin pregnancies occur in approximately 8% of patients using clomiphene citrate while the risk of triplet pregnancy is less than 1%. The risk of twin pregnancies with injectable gonadotropins is approximately 20% depending on the woman’s age, while the risk of triplets varies between 1% and 3%.
In IVF the risk of multiple pregnancies depends on the number of embryos transferred back to the uterus. Currently, guidelines of The Canadian Fertility and Andrology Society (2010) recommend that women aged 35 years or less, in their first or second IVF attempt, with at least 2 good quality embryos available for transfer, should be considered candidates for single embryo transfer. Patient and doctor can discuss the risk of multiples and decide on the number of embryos that is appropriate considering both patient’s choice and medical indications.
Multiple pregnancies, including twin pregnancies, are associated with significant risks, including pregnancy diabetes, maternal bleeding, premature labor,pregnancy-induced high blood pressure, Caesarean delivery (C-section) and low birth weights. Children born prematurely, or of low birth weight, may face a variety of health problems including lifelong learning difficulties.