When did I get pregnant?

[Anonyymmmmm]

LMP - 12th September 2025
(cycle 29/30 days)
DTD (did the deed) with A - 17th September ONLY
and
DTD (new partner) with B - 19th September onwards and now in relationship.

Period missed 11th October

positive clear blue digital “2-3 weeks” - 16th October

early scan (private) - 20th October - 5w 1 day gestation.

another scan (hospital) - 12 November - 8w 1/2 days gestation.

when did I conceive????
With the math I’m calculating late September so would be Partner B’s.

With only two days difference, that’s going to be a nightly difficult one to make an educated guess about. Unsettling as it is, I don’t think you’ll. be able to know for sure without a DNA test post birth.

if this pregnancy is something you’re happy about, congratulations.

Honestly. You’ll need a DNA on this one . Too close to call.

You absolutely won't know unless you do a dna test. Best wishes.

No pregnancy can be accurately dated within 48 hours. You can do a paternity DNA test but they are not cheap.

Agreed. DNA test required with this one.

Are they calculating dates from LMP…so 5w more like 3 if you see what I mean?
If so, I’d say B. I think people are missing the fact that you started sleeping with B on the 19th. You could have become pregnant subsequent to that date if I’m reading correctly?

48 hours isn’t enough to be able to tell by dates. My scans always came out with different dates up to about 12 weeks.

Too close together. Sperms can survive for days.

You can get a blood test done whilst pregnant (your blood) which can often rule out a man rather than matching him to the baby.

If LMP means first day of your last period then it’s unlikely to be partner A. You’re unlikely to have ovulated that early. Chances are it’s partner B’s.

If you plan to keep baby be honest with both. There's no shame in sleeping with A before you got together with B.

A DNA test is the only way to tell. Sperms can last up to five days in cervical mucus.

You need to be transparent with both guys and do the DNA once the baby is born.

The scans really aren't that accurate. I had my DD1 via IVF. I know exactly when she was conceived and implanted and my scan dates were always off.

Likely partner B's but you need a DNA test.

Even if A's sperm survived 5 days, it'd be conception on Sept 22nd. Which would have made you 4 weeks past conception on the scan at the 20th, which would have shown a gestational age of 6wks.

They're not 💯 precise though, and with only a week in the difference you'd want to be testing DNA asap.

It’s not just 2 days difference, 17th was only day 5/6 of my cycle the 19th onwards was when I started sleeping with B there was encounters pretty much every day through September and into October was what I was saying! ☺️

Yes that’s right I started with B on the 19th and then it was continuously after that we were active - the 17th would only have been day 5 of my cycle.

Why are you asking this question in December ? You’re already almost half way gone ! Do both the potential fathers know the situation ?

It only takes one sperm. Sperms can live for 5 day in cervical mucus. The only way to be certain is a DNA test. I understand you want the baby to be your current partners but we don't always get what we want. You need to be transparent now. It would be very wrong to suggest it is certainly either man's baby. All you can say is its 50:50.

I would say B as A may have been a little too early as you hadn't long finished your period then x

The gestation from scans includes an extra 14 days from conception, so the 5w1d from 20th October would actually be approximately 3w1d after conception (and the scan 3 weeks later, 8w1-2d, would be 5w1-d from conception). So, you would have conceived on or around 28th September. This would also fit with your cycle length as most women ovulate around 14 days before their next period, so around cycle day 15-16 for you.

I would not be placing much weight on this if you'd only had one early scan, as sometimes the measurements can be out or the pregnancy may not be developing properly, but given you've had two scans which indicate pretty much the same conception date I think you can be reasonably confident its partner B as 11 days would be too long for As sperms to survive.