Multiple Pregnancy- Features And Diagnosis

In Dizygotic twins, each twin has separate amnion and chorion and the intervening membrane consists of 4 layers amnion, chorion, chorion and amnion.

Ans. is d i.e. Diamniotic dichorionic

After embryonic disc fusion, conjoint twin is formed.

Ans. is c i.e. 1 in 80

According to Hellin’s rule

The mathematical frequency of multiple pregnancy is :

• Twins                     1 in 80
• Triplets                  1 in (80)2
• Quadruplets           1 in (80)³ and so on

Also know :

• The incidence of twins is highest in Nigeria (1 in 20).°
• It is lowest in far East countries.°
• Incidence in India – 1 in 80.°
• Incidence of twins is increasing in India because of the use of ovulation inducing drugs like clomiphene, gonadotrophins.°
• The incidence of monozygotic twins is constant throughout the world – 1 in 250.
• The incidence of dizygotic twins changes and is responsible for world wide variation in incidence.
• The incidence of Dizygotic twins increases with :

–     Increasing maternal age

–     Increasing parity

Family history of twinning

–     Ovulation induction with clomiphene citrate or gonadotrophins.

Ans. is b i.e. Twin peak in dichorionicity

“Chorionicity of the placenta is best diagnosed by ultrasound at 6 to 9 weeks of gestation. In dichoronic twins there is a thick septum between the chorionic sacs. It is best identified at the base of the membrane, where a triangular projection is seen. This is known as lambda or twin peak sign. Presence of lambda or twin peak sign indicates dichorionic placenta”

So it is clear that lambda / Twin peak sign clearly indicates dichorionic placenta & is hence the correct option ‘W. As far as other options are concerned.

Option a – Same sex rules out dichorionicity, this is incorrect because

Twins of opposite sex are almost always dizygotic dichorionic but same sex does not rule out dichorionicity. Option c – Thick membrane is present in monochrionic twins

This is also incorrect because monochorionic means there is a single chorion whereas dichorionic means there are 2 chorions so obviously dichorionic membrane will be thick.

“Monochorionic pregnancies have a dividing membrane that is so thin, it may not be seen until the second trimester. The membrane is generally less than 2mm thick & magnification reveals only 2 layers (of amnion)”

Option d – Chorionicity is best detected after 16 weeks –

Again this statement is incorrect because the best time to detect chrorionicity by USG is between 6 to 9 weeks.         

> 8 days

Diamnionic monochorionic

Vertex-vertex

B i.e. Same finger print

Ans: C i.e. Diamniotic monochorionic twins

Frequency of twins

• Frequency of conjoined twins (
• Frequency of M/M is 3%
• Frequency of D/M is 66%
• Frequency of D/D is 30%
• MC cause of mortality in twins is: Prematurity.

Ans. Superfecundation

• Fertilization of two ova discharged from the ovary at the same period of ovulationby two different acts of coitus committed at short intervals is superfecundation.

• The term is also used to refer to instances of two different males fathering fraternal twins, though this is more accurately known as heteropaternal super-fecundation.

• Medicolegal Aspect: Gross variations may occur in the complexion and features of the two babies and features of the two babies and may give rise to the dought of adultery and infidelity.

Ans. Comes from single egg

Ans. is ‘c’ i.e., Both of the above

• Superfecundation : Two ova are released in the same cycle get fertilized, either during the same act of coitus or during the separate acts. There is a possibility of the twin having two fathers.
• Superfaetation : (i) During the continuation of development of fetus, another ova released in a subsequent cycle get fertilized and starts developing as a second fetus. This can result in (a) Twin having two fathers, (b) Two children being born together with different stages of development, (c) Female may deliver twice within 1-3 months