Multiple Gestations (Part 1) For Ob/GYN Quiz On 4/1/11

Fraternal twins can be same sex or opposite sex because they are the result of two separate fertilized eggs. Each egg is fertilized by a different sperm, which means that the twins can develop with different genetic combinations. Therefore, it is possible for fraternal twins to be either the same sex or opposite sex.

Non-identical

Chorionicity refers to the number of chorions or placentas.

Monozygotic twins and identical twins are two terms that refer to the same phenomenon. These twins result from a single ovum being fertilized by a single sperm, leading to the development of two genetically identical individuals. Therefore, both "monozygotic, identical" and "identical, monozygotic" are correct ways to describe these twins.

**Due to shared placenta or cord entanglement.

Only same sex.

Dizygotic twin pregnancies have the least complications and account for approximately 70% of all twins.

During early pregnancy, it is easier to differentiate between monozygotic (identical) and dizygotic (fraternal) twins because the zygotes have not yet implanted in the uterus. In the first trimester, the zygotes have already implanted, making it more difficult to determine if they are monozygotic or dizygotic twins based on physical characteristics alone.

Amnionicity refers to the number of amniotic sacs. This term is used to describe the condition in which a pregnant individual is carrying multiple fetuses, each enclosed in its own amniotic sac. The number of amniotic sacs can vary depending on the type of multiple pregnancy, such as twins, triplets, or quadruplets. Understanding the amnionicity is important in prenatal care and delivery planning, as it can impact the management of the pregnancy and the potential risks involved.

Monozygotic twins, also known as identical twins, occur when a single fertilized egg splits into two embryos. These twins share the same genetic material and are always of the same sex. The given answer of 30 percent indicates that monozygotic twins account for 30 percent of all twins. This means that out of every 100 sets of twins, approximately 30 of them are monozygotic twins.

The timing of division from the point of conception is what determines amnionicity and chorionicity. This means that the specific time at which the embryo divides after conception will determine whether there are separate amniotic sacs and chorions (amnionicity and chorionicity) or if they remain undivided.

Twins that arise from two separate ova, fertilized by separate sperm cells are called dizygotic twins or fraternal twins. Dizygotic twins refers to twins that develop from two separate eggs, while fraternal twins refers to twins that develop from two separate sperm cells. Therefore, both options are correct and interchangeable.

Monozygotic twins, also known as identical twins, occur when a single fertilized egg splits into two embryos. This process is a random event and not influenced by hereditary factors. Therefore, monozygotic twins are not hereditary. However, assisted reproduction techniques such as in vitro fertilization (IVF) can increase the chances of having monozygotic twins. This is because during IVF, multiple embryos may be transferred to the uterus, increasing the likelihood of one or more of them splitting into identical twins.

After the zygote divides on day 8, it results in the formation of two embryos, which share a single amnion and a single chorion. This means that the embryos are monochorionic (they share the same outer membrane) and monoamniotic (they share the same inner membrane).

Monochorionic/diamniotic twins are the most common type of monozygotic twins, accounting for 70% of all monozygotic twins. In this type, the twins share a placenta (monochorionic) but have separate amniotic sacs (diamniotic). This occurs when the fertilized egg splits within the first four days after conception. The shared placenta provides the necessary nutrients and oxygen to both twins, while the separate amniotic sacs allow them to have their own space and movement.

The correct answer includes a comprehensive list of sonographic protocols for examining multiple gestations. These protocols involve conducting serial ultrasound exams every 3 to 4 weeks to monitor the growth of the fetuses, documenting the fetal heart rate, identifying the number of fetuses present, labeling the presenting fetus, identifying the presence of membranes, determining the number and location of placentas, identifying the fetal lie in pregnancy, determining separation, determining the gender (if different, indicating dizygotic twins), and performing biometry and fetal surveys for both fetuses. This thorough examination allows for the accurate assessment and monitoring of multiple pregnancies.

When there is only one placenta in a pregnancy, there is an increased risk for vascular complications. This is because the circulation of the placenta is shared between multiple fetuses, which can lead to issues with blood flow and nutrient exchange. These vascular complications can have negative effects on the health and development of the fetuses.

Zygotism refers to the process of fertilization and implantation of ova. It is the stage where the sperm fertilizes the egg, forming a zygote, which then implants itself in the uterus. This term specifically relates to the successful union of the sperm and egg, leading to the development of a new individual.

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Dizygotic twins, also known as fraternal twins, develop from separate fertilized eggs. Each twin has its own amniotic sac, called an amnion, which surrounds and protects the developing fetus. Additionally, each twin has its own placenta, which is responsible for providing nutrients and oxygen to the fetus. Therefore, dizygotic twins always have two amnions and two placentas.

The zygote divides between day 4 to day 8 post conception in monochorionic/diamniotic pregnancies. This means that the fertilized egg splits into two separate embryos during this time period. Monochorionic/diamniotic pregnancies occur when there is a single placenta but two separate amniotic sacs.

The correct answer includes several factors that are associated with an increased likelihood of dizygotic twinning. These factors include race, assisted reproduction (infertility agents), recent cessation of long term oral birth control, maternal age (35-40), maternal family history, multiparity (having multiple pregnancies), and maternal history of twinning. These factors have been found to have a correlation with the occurrence of dizygotic twinning.

The zygote divides in the first 3 to 4 days.

Multiple gestations, or pregnancies with more than one fetus, carry certain risks compared to singleton pregnancies. One of these risks is intrauterine growth restriction (IUGR), which refers to the poor growth of one or more fetuses. Another risk is vasa previa, a condition where the fetal blood vessels cross the entrance to the birth canal, making them vulnerable to rupture and severe bleeding. Premature labor, which is the onset of labor before 37 weeks of gestation, is also a risk in multiple gestations. Additionally, multiple gestations are associated with an increased risk of premature rupture of membranes (PROM), pregnancy-induced hypertension, and preeclampsia, which are conditions that affect blood pressure and can be harmful to both the mother and the fetus.