Medical Abortion in Very Early Pregnancy

Peter Kovacs, MD, PhD


March 27, 2018

Medical Abortion in Very Early Pregnancy

Despite the availability of highly effective contraceptive methods, approximately 50% of pregnancies are not planned, and about half of these are terminated.[1] For a long time, surgical methods of pregnancy termination were available: sharp or suction curettage in the first trimester of gestation, and dilatation and evacuation in the second trimester. Subsequently, medical options that interfere with the progesterone support (mifepristone) and induce uterine contractions (misoprostol) became available. Various doses, combinations, and routes of administration are in use. The efficacy of these medical options has been proven up until 9 weeks' gestation, and their use has been increasing.[2] Typically, before prescribing one of these medications, ultrasound is used to confirm the intrauterine location of the pregnancy, and laboratory or ultrasound follow-up is performed to document the completeness of the process.

In many cases, however, a decision to abort the pregnancy is made at a very early stage, when ultrasound cannot yet detect the pregnancy. The efficacy of medical options in very early pregnancy has not been well studied. A recent systematic review[3] evaluated the efficacy of medical abortion before 42 days of gestation.

Systematic Review Findings

The review summarizes the findings of six randomized controlled trials (RCTs) and nine prospective observational studies of mifepristone and misoprostol use for medical abortion. There is considerable heterogeneity with respect to the dose of mifepristone (50 mg-600 mg) or misoprostol (200 µg-800 µg) used and the route of misoprostol administration (oral, buccal, vaginal). The primary outcome in these studies was successful abortion (defined as no need for surgical procedures).

The pooled estimate of unsuccessful medical abortion was 0.02 (95% confidence interval [CI], 0.01-0.03) in the RCTs and 0.04 (95% CI, 0.03-0.06) in the observational studies. When the efficacy of medical abortion up to 42 days gestation was compared with that of medical abortion between days 43 and 49, no significant difference was found (RCTs: odds ratio [OR], 0.51; 95% CI, 0.21-1.27; observational studies: OR 0.9; 95% CI: 0.6-1.33). The investigators concluded that mifepristone and misoprostol provide effective medical abortion for very early pregnancies (up to 42 days).


Following successful fertilization and embryo cleavage, most blastocysts implant in the uterine cavity. In 1%-2% of pregnancies, however, the implantation occurs in extrauterine locations. Most clinically diagnosed pregnancies progress normally, but 15%-25% are miscarried, mostly as a result of random genetic errors.[4] In the case of intrauterine implantation around week 5 of gestation, the sac can be visualized. If pregnancy is not desired, termination involves a choice between surgical and medical methods. The decision is less obvious when the sac cannot yet be visualized and its intrauterine location cannot be confirmed.

Under well-controlled conditions using sedation and appropriate pain control, surgical termination of pregnancy is associated with minimal bleeding or pain. However, it can be associated with surgical complications (trauma, heavier bleeding, infection), which can lead to further interventions.

Medical abortion can be more painful because the products of conception have to be expelled from the uterus, and it is accompanied by prolonged bleeding. Still, medical abortion obviates surgical complications and is significantly cheaper.

This study showed that medical abortion is effective even in very early pregnancy, when the location of the pregnancy cannot be confirmed by ultrasound. Therefore, there is no need to delay the intervention. Compared with a later stage of pregnancy, medical abortion at an earlier stage may cause less pain and bleeding. Home use may be considered. Appropriate patient selection (no increased risk for or symptoms of ectopic pregnancy, appropriate follow-up to confirm successful abortion, patient compliance) is obviously important.