Negative attitudes toward abortion from health care providers are one of the main factors restricting access to the procedure, according to the researchers.
According to the World Health Organization (WHO), 1 in 5 pregnancies around the globe end in abortion - defined as the termination of pregnancy so it does not result in the birth of a baby.
In the US, a medical abortion procedure is an option in the early weeks of the first trimester, in which a woman receives a drug called methotrexate either orally or by injection, followed by oral or vaginal administration of a drug called misoprostol 3-7 days later.
In the second and third trimesters, only surgical abortion procedures - such as dilation and curettage or dilation and extraction - may be performed.
While surgical abortion procedures are very safe when performed legally under sufficient regulation, WHO estimate that for every 100 live births globally, around four unsafe abortions are performed - defined as a "procedure for terminating a pregnancy that is performed by an individual lacking the necessary skills, or in an environment that does not conform to minimal medical standards, or both."
Negative attitudes toward abortion remain a key barrier
For their study, Frances Doran and Susan Nancarrow, of the School of Health and Human Sciences at Southern Cross University in Australia, conducted a systematic review of more than 2,500 studies published between 1993 and 2014 that investigated access to abortion services in developed countries during the first 3 months of pregnancy.
Of these studies, the researchers identified 38 that involved early abortion and included views from both women and health care providers regarding factors that may be preventing women from accessing abortion services.
From their review, Doran and Nancarrow found that the main barriers to abortion services cited by health care providers were moral opposition to abortion, lack of sufficient training, lack of health care professionals able to carry out the procedure, insufficient hospital resources - primarily in rural areas - and harassment of medical staff by individuals opposed to abortion.
Women included in the studies cited health care professionals' negative attitudes toward abortion, the cost of the procedure - particularly in North America - as barriers to abortion services. A lack of local abortion services was also named as a key barrier, especially among low-income women, those living in rural areas and those from minority groups.
Commenting on their findings, the researchers say:
"Despite the safety and frequency with which legal, regulated abortions are performed, this review identifies several avoidable factors that limit the provision of, and access to, abortion services."
How can these barriers be broken down?
The team points to a number of ways to increase access to abortion services, including providing appropriate training of health care providers in how to treat women wishing to have an abortion in early pregnancy.
"Negative attitudes and beliefs of health professionals toward abortion create obstacles for women seeking access to abortion," they note. "Regardless of practitioner values, they should be trained to refer appropriately, and provide services that are in the best interests of the woman."
Doran and Nancarrow say making abortion services free or affordable to women to avoid requiring referral could be another way to increase access, as could providing abortion services that are part of a multidisciplinary clinic to lower associated stigma.
The researchers also point out that increasing access to medical abortion may also boost access to the procedure during early pregnancy, noting that in some countries - such as Canada - medical abortion is unlicensed.
"The provision of medical abortion via telemedicine has clear benefits for the woman and the provider with excellent clinical outcomes," they add.
"Furthermore, if women could procure safe medical abortifacients from non-physician providers outside their local community, or in an outpatient medical setting, termination then becomes a private decision between the doctor and the patient, which is less susceptible to the outside scrutiny of external conservative anti-abortion attitudes and pressures."
In February, Medical News Today reported on a WHO study that found low contraception in 35 low- and middle-income countries is behind 15 million unwanted pregnancies globally every year.