The most basic information a maternity nurse should have concerning conception is that:

Correct Answer: D

Rationale: The correct answer is D) Implantation in the endometrium occurs 6 to 10 days after conception. This is the most basic information a maternity nurse should know about conception because it highlights the timeline of events following fertilization. After conception, the fertilized egg undergoes several divisions as it travels down the fallopian tube towards the uterus. Implantation occurs when this developing embryo attaches to the thickened lining of the uterus, known as the endometrium. Option A is incorrect because ova are typically fertile for about 12-24 hours after ovulation, not 48 to 72 hours. Option B is also incorrect as sperm can remain viable in the female reproductive tract for up to 5 days, not just 12 to 24 hours. Option C is incorrect as conception actually occurs when the genetic material of the sperm combines with the genetic material of the ovum, forming a zygote, rather than when the sperm penetrates the ovum's membrane. Understanding the timing of events during conception and early pregnancy is crucial for maternity nurses to provide accurate information and support to expectant mothers. This knowledge helps in assessing and monitoring the progression of pregnancy, identifying any potential issues, and offering appropriate care and guidance to pregnant women.

Correct Answer: A

Rationale: The correct answer is A) Contact between maternal blood and fetal capillaries within the chorionic villi. The placenta acts as a barrier between the maternal and fetal circulations while allowing for the exchange of oxygen, nutrients, and waste products. Within the chorionic villi, small finger-like projections of the placenta, maternal blood comes into close contact with fetal capillaries, facilitating the transfer of these essential substances. Option B) Interaction of maternal and fetal pH levels within the endometrial vessels is incorrect because pH levels do not directly facilitate the exchange of substances between the mother and fetus. Option C) A mixture of maternal and fetal blood within the intervillous spaces is incorrect as maternal and fetal blood do not mix in the placenta due to the presence of the placental barrier. Option D) Passive diffusion of maternal carbon dioxide and oxygen into the fetal capillaries is incorrect because while passive diffusion does occur, it is the contact between maternal blood and fetal capillaries within the chorionic villi that allows for this exchange to take place efficiently. Understanding the intricacies of placental function is crucial in comprehending the physiological processes that support fetal development. By grasping how the placenta facilitates the exchange of substances between the mother and fetus, healthcare professionals can better address issues that may arise during pregnancy and ensure optimal maternal and fetal health.

Correct Answer: A

Rationale: In a normal umbilical cord, there should be two vessels present - one artery and one vein. The most common finding is having one umbilical vein and two umbilical arteries, but it is also considered within normal limits to have one artery and one vein. This is important as an abnormal number of blood vessels in the umbilical cord can indicate potential issues like congenital abnormalities or genetic conditions.

Correct Answer: C

Rationale: During early development of the fetus, the umbilical cord is relatively larger compared to later stages of pregnancy. This is because the umbilical cord plays a crucial role in providing necessary nutrients, oxygen, and removing waste products from the developing baby. As the pregnancy progresses, the blood vessels in the umbilical cord mature and shrink in diameter, leading to a decrease in its overall size compared to the early stages. The larger size of the umbilical cord in early pregnancy facilitates efficient nutrient exchange between the mother and the developing fetus, supporting the baby's growth and development.

Correct Answer: C

Rationale: Dizygotic twins, also known as fraternal twins, result from the fertilization of two separate eggs by two sperm cells. Therefore, they have different genetic makeups and can be the same sex or different sexes. This is in contrast to monozygotic twins (identical twins), who arise from a single fertilized egg that splits into two embryos, resulting in twins of the same sex and identical genetic makeup. It is important for the nurse to include this information in the staff in-service on multifetal pregnancy to ensure accuracy and understanding among the attendees.