while abortion rates usually decline with increasing usage of modern contraceptives westoff shah and ahman they may rise due to a strong desire for smaller family size during periods of rapid fertility decline studies have shown an association between fertility transition and unwanted pregnancy in some developing countries indicating a rise in unwanted pregnancies during the fertility transition and remaining relatively high until the end of the transition period bankole and westoff bongaarts contrary to other countries the substantial fertility decline in the islamic republic of iran has been accompanied by only a moderate rise in the age at first birth which increased from years in the s to years in the s abbasishavazi and hosseinichavoshi