A 30-year-old woman presents to the emergency department with severe abdominal pain and vaginal bleeding for the past 6 hours. She reports a history of irregular menstrual cycles. She has been sexually active without using contraception and reports a positive home pregnancy test 2 weeks ago. Past medical history is otherwise unremarkable, and she does not take any medications. Vital signs are temperature 38.6°F (37.0°C), blood pressure 92/58 mmHg, pulse 128 beats/min, and respirations 22/min. On physical examination, she appears pale and diaphoretic. Abdominal examination reveals tenderness in the right lower quadrant with rebound tenderness. A pelvic examination is deferred due to the patient's discomfort. Transvaginal ultrasound demonstrates an empty uterus and fluid in the cul-de-sac.
Which of the following was the most likely site of implantation of the blastocyst in this patient?
The correct answer is:
C) Fallopian tube
Implantation of the blastocyst typically occurs in the endometrium of the uterus. However, in cases of ectopic pregnancy, implantation occurs in an abnormal location, most commonly within the fallopian tube. This can result in abdominal pain, vaginal bleeding, and signs of hemodynamic instability.
Answer choice A: Cervix is incorrect. Implantation does not typically occur in the cervix; it primarily serves as a passage for sperm to enter the uterus.
Answer choice C: Endometrium, is incorrect. The endometrium is the normal site of blastocyst implantation in the uterus during a normal pregnancy.
Answer choice D: Fimbriae, is incorrect. The fimbriae are finger-like projections at the ends of the fallopian tubes closes to the ovaries. They catch and sweep eggs into the fallopian tubes.
Answer choice E: Ovary, is incorrect. Implantation does not typically occur in the ovary. Ovulation occurs in the ovary. Fertilization usually occurs in the fallopian tube, and implantation most commonly occurs in the uterus.
Key Learning Point
The blastocyst implants into the endometrium during a normal pregnancy. If implantation occurs in an abnormal location (e.g., the fallopian tube), it is termed an ectopic pregnancy.
