Due date reliability: HPT or ultrasound scan results?

I was wondering which method of calculation of a baby's due date is more accurate...My wife had her (first day of her) last period on Dec 19. That period was already delayed by a week; her period should have arrived on Dec 12 (usually she's on time, rarely misses her periods but she got cold in early dec and we thought that's why it was delayed). Anyway, at ultrasound the doctor asked her about her last period and my wife told the doc it was Dec 19. After measuring the twin babies inside with ultrasound, he then proceeded to tell my wife that she is 7 weeks and 5 days pregnant--that means she got pregnant around Jan 2, as he indicated.

Back home, I then checked several baby due date calculators on the net and all indicated that if a womans last period was on Dec 19, she must have gotten pregnant on Jan 2 and is due by Sept 25 (standard 40-week delivery). That was in line with what the doc had told her. BUT, we also used HPTs with 20MIUs (that is quite sensitive) several times between early Jan and Jan 24; on Jan 24 the test was still negative. She then took the test on Jan 29 and only then was it positive. She reconfirmed that result the following day (Jan 30).

I've heard that HPTs are like 97 percent accurate and confirm pregnancy 7 to 10 days (or even before depending on its level of sensitivity) since conception has taken place. Then why that test turned out negative--as late as Jan 24--if she concieved on Jan 2? I have no clue and I suspect she got pregnant not before mid- to the third week of Jan and the ultrasound doc just relied on her period data and that pregnancy occurs in mid cycle most of the time (although he also took scan measurements)...Although another doc in the same clinic, who took physical measurements of her stomach thereafter also said that she apparently conceived on Jan 1-2, although that doc first looked at ultrasound reports before saying that.

The reason I want to know her exact conception (and hence approximate due) date is because she's pregnant with twins and if she needs c-section we want to avoid pre-term labor, if we plan a c-section.

So is it possible for a women to conceive on Jan 2 and highly sensitive HPTs don't turn positive until after Jan 29th? Should we relay on ultrasound records and the following physical measurment of her belly or do we look at HPT results?

Sorry for asking you to read this much

 

Here's a little info for you...
a woman's cycle is different from the next woman's. The day her period first started is cycle day one (CD1), doctors go under the assumption that she would've ovulated on CD14 but that is generally inaccurate.
For example... my last cycle lasted 33 days and I ovulated on CD20. It would be hard to get an exact date of implantation (when the fertilized egg attaches itself to the womb) unless your wife knew when she ovulated.
The online calculators also use the 14th day as a guide. If your wife can remember any signs her body gave her then that would be helpful, eg. if she had any spotting before her period was due, or cramps that felt like period pains. Also (I don't mean to gross you out), her cervical fluid plays a big part in giving signs of ovulation.

It's really hard for me to help here... how long are her cycles usually? Are they the normal 28 days? Or are they very irregular?
This kind of thing can get really personal, maybe too personal to talk about on a website!
You can pm me if you want, so I can ask you those personal questions.

PS - CONGRATULATIONS!

 

Thanks. I somehow think that she conceived later than Jan 2. Yes, she usually has a regular cycle: on Sep 8 Oct 10 Dec 12...has a pattern, with a period lasting 5 days...her period was only delayed in Dec by one week (that was an exception from that pattern in a long time, she was running a tempreture in early dec--she got cold--and we also considered that she could have been pregnant until her period came on Dec 19--a week delay). Unfortunately, she could not really recognize the times of her fertility, e.g. the density of her vaginal fluids or another signs, she hasn't been very experienced in that, so we mostly relied on HPTs...and HPT turned positive only on Jan 29...go figure. feel free to discuss this issue in this thread. Thanks again!

 

hey have you thought about going to a Midwife instead of your local doctor..you most llikely would be able to avoid a C-Section which puts alot of trama on the baby and the mother just a thought

 

Ultrasound is very accurate before about 18 weeks at determining conception and due date. Some mothers just don't develop enough HCG in the early weeks of the pregnancy, to be detected, even by the most sensitive tests.

I don't understand how scheduling a C Section will prevent preterm labor. It makes no sense. I had preterm labor with all my babies (all singletons) and FULL bedrest, from about 16 weeks was the only thing that allowed me to carry to term. Scheduling a C Section doesn't prevent preterm labor.

One more thing to remember, most healthy, head down at labor twins, who are over 28 weeks CAN be delivered vaginally. Also, nearly 50% of twins are born within 4 weeks of 40 weeks, so not ALL twin pregnancies are preterm. Only about half are.

She should probably stop working NOW, and get as much fluid and rest as possible. Bed rest means BED rest (or couch rest) most of the womyn I know or work with who have delivered preterm have cheated on their bed rest. No one thought I would carry ANY of my babies to term (I start contracting at about 12 weeks) but I am vigilent about my bed rest, and my fluid intake, and my doctor has an excellent record of vaginal birth twins, vaginal breech births, and keeping moms pregnant until the babies are ready to be born.

If your doctor is talking about a section this early, it is really time to see someone else. Either a good midwife (one with hospital privleges would be helpful if her pregnancy turns high risk, so you won't have to change HCPs) or a good OB at a major University Hospital is the best bet.

I wouldn't deliver at a community hospital. Their NON high risk C sec rates and intervention rates are just too high.

 

Thank you. I see...

Sure, it doesn't...I wasn't very clear. No, she doesn't work. She gets about 8 to 10 hours sleep at night, and she rests lying on her bed about 2-4 hours during the day. She's usually on her feet the rest of the time (about 10 to 14 hours per day--either staying at home or outside). Is this sufficient bed rest or should she lie down more hours? (she's 8+weeks pregnant; she drinks enough water)

Thanks!

 

Right now, she will not go into preterm labor, and bed rest is not neccesary for all multiple moms, but if she has ANY contractions after 12 weeks or so, she should consider talking to her HCP about bedrest, or at least taking it really easy.

Right now, her pregnancy is to young to have "labor" but as the babies grow, the risk of preterm labor will increase. Like I said, half of all twins are born near term, so it isn't written in stone, but bed rest is NOT 10 hours day on your feet. IF and when she starts having contraction, cramps or any other high risk things, FULL bedrest, meaning being on your left side for the ENTIRE day is what Bed Rest is.

Now, she can do what she wants, if she has no contractions early, she will stilll have to take easy, but if she has ANY preterm contractions, IMO (as a mom who carried four high risk pregnancies to term, against the odds) FULL bed rest is really a good thing. For now, she can do what she is comfortable doing. Exercise is good, unless contractions start. Then, it's off your feet until the babies are term (that is about 36 weeks or so) I spent up to 6 months on TOTAL bedrest with my pregnancies. As bad as this was, nothing is as bad as having a baby in the NICU.

For now, though, she's OK to do what she is comfortable doing. Fluids are really important during pregnancy, especially when you are carrying more than one baby.

I'd maybe look for an other HCP, this one is giving you some weird advice. There is simply no way he could "know" she will need a section. Twins can be and are delivered vaginally.

Good luck.

 

Gotta. Thanks.

I see...No, its not the doc that gives her that advice. It's mostly us--a friend of hers and myself--that are considering various situations (her friend is very pro C-section but we really aren't).

 

I wanted to have a midwife, but sadly, twin pregnancies are considered high risk, so I felt that it was safer for my babies to just have a regular doctor that specialized in HRP. Several people with twins have gone to midwives and haven't had any problems. I guess it's just a personal choice.