A woman diagnosed with marginal placenta previa gave birth vaginally 15 minutes ago. At the present time she is at the greatest risk for:

Choice A reason: A fetal heartbeat auscultated with a Doppler or a fetoscope is a positive sign of pregnancy, as it confirms the presence of a living fetus in the uterus. A Doppler is an electronic device that uses sound waves to detect the fetal heart rate, while a fetoscope is a stethoscope-like instrument that amplifies the fetal heart sounds. The fetal heartbeat can be heard as early as 10 to 12 weeks of gestation with a Doppler and 18 to 20 weeks of gestation with a fetoscope.

Choice B reason: Quickening is the first perception of fetal movement by the pregnant woman, usually felt between 16 and 20 weeks of gestation for first-time mothers and 13 to 16 weeks of gestation for experienced mothers. However, quickening is not a positive sign of pregnancy, as it can be subjective and mistaken for other sensations, such as gas, hunger, or muscle spasms².

Choice C reason: Morning sickness is a common symptom of pregnancy that involves nausea and vomiting, usually in the first trimester. However, morning sickness is not a positive sign of pregnancy, as it can be caused by other factors, such as food poisoning, stress, or medication.

Choice D reason: A positive pregnancy test is a probable sign of pregnancy, not a positive sign. A pregnancy test detects the presence of human chorionic gonadotropin (hCG), a hormone produced by the placenta, in the urine or blood of the woman. However, a positive pregnancy test does not guarantee a viable pregnancy, as it can be influenced by the timing, the quality, or the interpretation of the test. A positive pregnancy test can also occur in cases of ectopic pregnancy, molar pregnancy, or miscarriage.

Choice A reason: Syphilis is a bacterial STI caused by Treponema pallidum. It is characterized by three stages: primary, secondary, and tertiary. It can cause serious complications such as neurosyphilis, cardiovascular syphilis, and congenital syphilis. However, it is not the most common bacterial STI.

Choice B reason: Candidiasis is a fungal infection caused by Candida albicans. It is not a STI, but rather an opportunistic infection that can affect the vagina, mouth, skin, or other mucous membranes. It can cause symptoms such as itching, burning, discharge, and inflammation.

Choice C reason: Gonorrhea is a bacterial STI caused by Neisseria gonorrhoeae. It can infect the urethra, cervix, rectum, throat, or eyes. It can cause symptoms such as dysuria, discharge, pelvic pain, and bleeding. It can also lead to complications such as pelvic inflammatory disease, epididymitis, infertility, and disseminated gonococcal infection. However, it is not the most common bacterial STI.

Choice D reason: Chlamydia is a bacterial STI caused by Chlamydia trachomatis. It is the most common bacterial STI, affecting about 2.86 million people in the United States in 2018. It can infect the urethra, cervix, rectum, throat, or eyes. It can cause symptoms such as dysuria, discharge, pelvic pain, and bleeding. It can also lead to complications such as pelvic inflammatory disease, epididymitis, infertility, and ectopic pregnancy.