The hormone responsible for a positive pregnancy test is:

HP CHO -9 October 2022

Obstetrics & Gynaecology

Easy

Appeared in: HP CHO -9 October 2022

Explanation

Human Chorionic Gonadotropin (hCG) is a glycoprotein hormone produced by the syncytiotrophoblast cells of the placenta after implantation.
The detection of hCG in a woman's blood or urine is the basis for all modern pregnancy tests.
hCG's primary function in early pregnancy is to maintain the corpus luteum, ensuring it continues to secrete progesterone, which is vital for sustaining the uterine lining.
hCG levels rise exponentially in the first trimester, typically doubling every 48-72 hours, making it a reliable and early marker of pregnancy.

Option A: Estrogen is a crucial hormone for maintaining pregnancy, but it is also present in significant amounts during the normal menstrual cycle. Its levels do not rise as rapidly or as uniquely as hCG in early pregnancy, making it an unsuitable marker for pregnancy tests.
Option B: Progesterone is essential for preparing and maintaining the uterine lining for pregnancy. While its levels are elevated during pregnancy, they are also high during the luteal phase of a non-pregnant cycle, so it cannot be used to definitively diagnose pregnancy.
Option D: Follicle-stimulating hormone (FSH) is secreted by the pituitary gland and its main role is to stimulate the growth of ovarian follicles before ovulation. During pregnancy, high levels of estrogen and progesterone provide negative feedback to the pituitary, causing FSH levels to be very low.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal basis of pregnancy detection as background academic context rather than a clinical decision trigger.
A key nursing responsibility is educating patients on the correct timing and procedure for home pregnancy tests, such as using first-morning urine for the highest hCG concentration.
Nurses must understand the significance of quantitative hCG levels. A slow-doubling time can be an early warning sign of an ectopic pregnancy or non-viable gestation, requiring prompt medical evaluation.
What if? If a patient has a positive pregnancy test but experiences vaginal bleeding and cramping, the nurse should anticipate orders for serial quantitative hCG blood tests and a transvaginal ultrasound to differentiate between a threatened miscarriage, an ectopic pregnancy, or a normal early pregnancy.

How to Approach the Question

Identify the core of the question: It asks for the specific hormone that pregnancy tests detect.
Recall the basic physiology of early pregnancy. After implantation, the developing placenta begins to produce a unique hormone.
Consider the function of each hormone listed. Estrogen and progesterone are key pregnancy hormones but are also present in non-pregnant cycles. FSH is involved in ovulation, not pregnancy maintenance.
Recognize that Human Chorionic Gonadotropin (hCG) is produced almost exclusively during pregnancy by the chorionic villi of the placenta.
Conclude that hCG is the specific marker used in pregnancy tests because its presence confirms the existence of placental tissue.

Concept Tested & Keywords

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