Worldwide, on average, abortion is safer than carrying a pregnancy to term. A 2007 study reported that "26% of all pregnancies worldwide are terminated by induced abortion," whereas "deaths from improperly performed [abortion] procedures constitute 13% of maternal mortality globally." In Indonesia in 2000 it was estimated that 2 million pregnancies ended in abortion, 4.5 million pregnancies were carried to term, and 14-16 percent of maternal deaths resulted from abortion.In the US from 2000 to 2009, abortion had a mortality rate lower than plastic surgery, lower or similar to running a marathon, and about equivalent to traveling 760 miles (1,220 km) in a passenger car. Five years after seeking abortion services, women who gave birth after being denied an abortion reported worse health than women who had either first or second trimester abortions. The risk of abortion-related mortality increases with gestational age, but remains lower than that of childbirth. Outpatient abortion is as safe from 64 to 70 days gestation as it before 63 days.There is little difference in terms of safety and efficacy between medical abortion using a combined regimen of mifepristone and misoprostol and surgical abortion (vacuum aspiration) in early first trimester abortions up to 10 weeks gestation. Medical abortion using the prostaglandin analog misoprostol alone is less effective and more painful than medical abortion using a combined regimen of mifepristone and misoprostol or surgical abortion.Vacuum aspiration in the first trimester is the safest method of surgical abortion, and can be performed in a primary care office, abortion clinic, or hospital.
This is particularly true for cervical cancer, the most common type of which occurs in 1 of every 2,000–13,000 pregnancies, for which initiation of treatment "cannot co-exist with preservation of fetal life (unless neoadjuvant chemotherapy is chosen)". Very early stage cervical cancers (I and IIa) may be treated by radical hysterectomy and pelvic lymph node dissection, radiation therapy, or both, while later stages are treated by radiotherapy. Chemotherapy may be used simultaneously. Treatment of breast cancer during pregnancy also involves fetal considerations, because lumpectomy is discouraged in favor of modified radical mastectomy unless late-term pregnancy allows follow-up radiation therapy to be administered after the birth.Exposure to a single chemotherapy drug is estimated to cause a 7.5–17% risk of teratogenic effects on the fetus, with higher risks for multiple drug treatments. Treatment with more than 40 Gy of radiation usually causes spontaneous abortion. Exposure to much lower doses during the first trimester, especially 8 to 15 weeks of development, can cause intellectual disability or microcephaly, and exposure at this or subsequent stages can cause reduced intrauterine growth and birth weight. Exposures above 0.005–0.025 Gy cause a dose-dependent reduction in IQ. It is possible to greatly reduce exposure to radiation with abdominal shielding, depending on how far the area to be irradiated is from the fetus.The process of birth itself may also put the mother at risk.