The nurse is counseling a patient over the phone about the benefits of using ovulation predictor kits (OPKs) when trying to conceive.
The nurse explains that OPKs detect, at the time of ovulation, a spike in which of the following hormones?

Choice A rationale

A Pap smear, or Papanicolaou test, is a screening procedure for cervical cancer. It involves collecting cells from the cervix to detect abnormal cell changes, often caused by human papillomavirus (HPV) infection. While important for gynecological health, it does not assess the patency, or openness, of the fallopian tubes, which are distinct anatomical structures involved in ovum transport.

Choice B rationale

Hysterosalpingography (HSG) is a diagnostic procedure using X-rays to visualize the uterus and fallopian tubes. A contrast dye is injected into the uterus, filling the uterine cavity and fallopian tubes. If the tubes are patent, the dye will spill into the peritoneal cavity, indicating no obstruction and allowing for the assessment of their structural integrity for fertility evaluation.

Choice C rationale

Exploratory laparoscopy is a surgical procedure involving small incisions and the insertion of a laparoscope to directly visualize the pelvic organs, including the fallopian tubes. While it can confirm tubal patency and identify other pelvic pathology, it is more invasive than HSG and typically reserved for cases where less invasive tests are inconclusive or when concurrent treatment is needed.

Choice D rationale

Hysteroscopy is a procedure that uses a thin, lighted telescope (hysteroscope) inserted into the uterus through the vagina and cervix to visualize the uterine cavity. It is primarily used to diagnose and treat intrauterine conditions like polyps, fibroids, or adhesions, which can affect fertility by interfering with implantation, but it does not directly assess the patency of the fallopian tubes themselves.

Choice A rationale

Monozygotic twins originate from a single zygote, which forms from the fertilization of one egg by one sperm. This single zygote subsequently divides into two genetically identical embryos. Therefore, the statement "That means there was only one egg" accurately reflects the biological basis of monozygotic twinning, as opposed to dizygotic twins arising from two separate eggs.

Choice B rationale

Monozygotic twins are colloquially known as "identical twins" because they develop from a single fertilized egg that splits. This results in two individuals who share nearly identical genetic material, leading to very similar physical characteristics. The patient's statement "We are having identical twins! How lovely" correctly identifies this key characteristic of monozygotic twinning.

Choice C rationale

Given that monozygotic twins are genetically identical and thus physically very similar, distinguishing between them can often be challenging, especially in infancy. Their shared genetic makeup means they typically have the same blood type, hair color, eye color, and often similar fingerprints, making the question of how to tell them apart a common and valid concern for parents.

Choice D rationale

Monozygotic twins arise from a single zygote, meaning they share the same genetic sex chromosomes (XX for female or XY for male). Therefore, they will always be of the same sex, either both girls or both boys. The statement "It's possible they could both be girls or boys, or one of each" is incorrect because it implies the possibility of different sexes, which only occurs in dizygotic (fraternal) twins.