Question:medium
A pregnant female comes to a gynecologist who sends her for USG. On USG twin pregnancy noted with about one month difference in age of fetuses. Which is true of following
A pregnant female comes to a gynecologist who sends her for USG. On USG twin pregnancy noted with about one month difference in age of fetuses. Which is true of following
Show Hint
Two fetuses one month apart in age means the second ovum was fertilised in a later menstrual cycle – which single term describes that?
Updated On: Jun 22, 2026
- Superfetation
- Superfecundation
- Suppositious child
- Posthumous child
Show Solution
The Correct Option is A
Solution and Explanation
Clinical reasoning - anchor on the age gap.
The decisive clue is that the two fetuses differ in gestational age by about one month. The mechanism that creates two fetuses of UNEQUAL age in one uterus must involve conception happening at two SEPARATE times.
Why superfetation fits: Superfetation means a woman who is already pregnant ovulates again in a subsequent cycle, that second ovum is fertilised, and a second conceptus implants. Because the two conceptions are separated by about a menstrual cycle, the fetuses are roughly $4$ weeks apart in age - precisely the ultrasound finding.
Contrast with superfecundation: In superfecundation two ova from the SAME ovulatory cycle are fertilised, possibly by sperm from two coital acts (even two fathers), but both conceptions occur within the same cycle, so the twins are the SAME age. The one-month gap rules this out.
Why the parentage terms are irrelevant:
- A suppositious child is a fabricated/pretended birth where a woman claims to have delivered a baby she never carried - a fraud issue, not an embryology issue.
- A posthumous child is one delivered after the father has died, defined by timing relative to paternal death, not by any difference in twin ages.
Since only superfetation explains two intrauterine fetuses of clearly different ages, that is the correct choice.
Answer: A (Superfetation).
The decisive clue is that the two fetuses differ in gestational age by about one month. The mechanism that creates two fetuses of UNEQUAL age in one uterus must involve conception happening at two SEPARATE times.
Why superfetation fits: Superfetation means a woman who is already pregnant ovulates again in a subsequent cycle, that second ovum is fertilised, and a second conceptus implants. Because the two conceptions are separated by about a menstrual cycle, the fetuses are roughly $4$ weeks apart in age - precisely the ultrasound finding.
Contrast with superfecundation: In superfecundation two ova from the SAME ovulatory cycle are fertilised, possibly by sperm from two coital acts (even two fathers), but both conceptions occur within the same cycle, so the twins are the SAME age. The one-month gap rules this out.
Why the parentage terms are irrelevant:
- A suppositious child is a fabricated/pretended birth where a woman claims to have delivered a baby she never carried - a fraud issue, not an embryology issue.
- A posthumous child is one delivered after the father has died, defined by timing relative to paternal death, not by any difference in twin ages.
Since only superfetation explains two intrauterine fetuses of clearly different ages, that is the correct choice.
Answer: A (Superfetation).
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