# Babies are carried for nine months. Or ten. Care to help two childless writers out? **URL:** \ **Category:** Factual Questions\ **Created:** [December 12, 2003, 12:43am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475 "2003-12-12T00:43:55Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![elfkin477](https://avatars.discourse-cdn.com/v4/letter/e/a9a28c/32.png) [@elfkin477](https://boards.straightdope.com/u/elfkin477)\ **Post date:** [December 12, 2003, 12:43am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/1 "2003-12-12T00:43:55Z")
I’m writing a story with a friend for kicks, but since people are actually reading it, we’d like to be as accurate as possible. Sadly, neither of us quite understands the nine months but ten months deal. If our character is going to concieve a baby the first week of January would the baby be due… early or late October? Does adding forty weeks to whatever the conception date is give a good estimate of when a baby is due, or is it harder to work out than that? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [December 12, 2003, 12:49am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/2 "2003-12-12T00:49:18Z")
[Calculating Due Date.](http://www.paternityangel.com/Articles_zone/How_it_happens/How-6.htm) ---
**Author:** ![antechinus](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@antechinus](https://boards.straightdope.com/u/antechinus)\ **Post date:** [December 12, 2003, 1:38am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/3 "2003-12-12T01:38:20Z")
I actually researched this a few months ago and posted [in this thread.](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=184953) A paper (AM J OBSTET GYNECOL 1993;168:480-4) was published in 1993 by Mittendorf et al, which statistically analysed a sample of deliveries (n=9355) and came up with an algorithm to more accurately predict delivery date. GL = 256.447 + 1.5648_age - 0.0259_age^2 + 0.1295\*ponderal index Much better than the 200 year old Naegels rule, that is commonly used. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [December 12, 2003, 2:35am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/4 "2003-12-12T02:35:05Z")
The “typical” pregnancy supposedly lasts 280 days – ten _lunar_ months of 28 days, or nine calendar months of 30-31 days, plus a smidge. Obviously folks have already given more precise modes of calculation that take individual differences into account – but that’s the sense behind the nine/ten month dichotomy. ---
**Author:** ![Quint](https://avatars.discourse-cdn.com/v4/letter/q/76d3ee/32.png) [@Quint](https://boards.straightdope.com/u/Quint)\ **Post date:** [December 12, 2003, 3:48am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/5 "2003-12-12T03:48:52Z")
Another aspect of this is the calculation of the start of the pregnancy, which is considered to be the end of the woman’s last period. Given that the majority of women ovulate roughly 2 weeks after this, it can get confusing. Let’s say your characters had intercourse only one time, on January 3rd. The actual “date of conception” would be from the end of the female character’s last period, most likely roughly 2 weeks before the act (say December 21). Something to consider if factual accuracy is your ultimate goal. ---
**Author:** ![antechinus](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@antechinus](https://boards.straightdope.com/u/antechinus)\ **Post date:** [December 12, 2003, 6:00am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/6 "2003-12-12T06:00:31Z")
There are also real lunar months (29.53 days) and fudge lunar months (28 days). **Polycarp** The ten lunar month thing is the time from _the first day of the mothers last menstrual cycle_, which means the actual gestational period is ~ 10 x 28 minus two weeks for the time between menstruation and ovulation = 266 days. (according to this method of estimation). But of course average gestation is closer to 274 days (based on empirical evidence of the Mittendorf study). ---
**Author:** ![antechinus](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@antechinus](https://boards.straightdope.com/u/antechinus)\ **Post date:** [December 12, 2003, 6:15am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/7 "2003-12-12T06:15:41Z")
oh and of course the 2 weeks from menstuation to ovulation can vary quite a bit. So using the **rough and ready method** for birth date: From Menstruation 10.0 fudge lunar months 9.5 real lunar months 9.2 calander months From Conception 9.5 FLM 9.0 RLM 8.7 CM Using **274 day gestation** from conception: 9.8 FLM 9.3 RLM 9.0 CM ---
**Author:** ![elfkin477](https://avatars.discourse-cdn.com/v4/letter/e/a9a28c/32.png) [@elfkin477](https://boards.straightdope.com/u/elfkin477)\ **Post date:** [December 16, 2003, 7:42pm UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/8 "2003-12-16T19:42:19Z")
Thanks! Follow up question though: If a premie is a “24-weeker” do they mean the baby has been developing for 24 weeks, or mom’s last period was 24 weeks ago? Because if it’s the latter…wow. ---
**Author:** ![Moirai](https://avatars.discourse-cdn.com/v4/letter/m/96bed5/32.png) [@Moirai](https://boards.straightdope.com/u/Moirai)\ **Post date:** [December 16, 2003, 10:18pm UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/9 "2003-12-16T22:18:48Z")
I think that’s gestation time on the preemie. But is a 24 week preemie viable? ---
**Author:** ![Aspidistra](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aspidistra/32/3894_2.png) [@Aspidistra](https://boards.straightdope.com/u/Aspidistra)\ **Post date:** [December 16, 2003, 10:33pm UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/10 "2003-12-16T22:33:12Z")
When I was having a hospital tour before the birth of my baby, there were pictures up on the walls of prem babies who had previously been born there (and survived). The youngest was 23 weeks. ---
**Author:** ![domesticatedjunglefowl](https://avatars.discourse-cdn.com/v4/letter/d/b38774/32.png) [@domesticatedjunglefowl](https://boards.straightdope.com/u/domesticatedjunglefowl)\ **Post date:** [December 17, 2003, 1:05am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/11 "2003-12-17T01:05:10Z")
My parents told me i was born at 7 months. I was born at 8 pounds though. Is that likely or even possible by any of these calculations? ---
**Author:** ![Ca3799](https://avatars.discourse-cdn.com/v4/letter/c/9f8e36/32.png) [@Ca3799](https://boards.straightdope.com/u/Ca3799)\ **Post date:** [December 17, 2003, 1:37am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/12 "2003-12-17T01:37:03Z")
I like to use weeks for accuracy. 38 to 42 weeks is considered ‘term’, though most Doctor’s won’t let you get to 42 weeks. I have a son born at 23.5 weeks who is 6, in kindergarten, and without apparant deficits. We’ve been pretty fortunate. Where I work, we’ve had three 22 week survivors over about 6 years, but I don’t know how long two of them survived or how they are doing. I did see one, who was only 8 months old at the time. She still had apnea, oxygen, tube feeding, and appeared to have significant brain damage, although I did not ask the mother about her. ---
**Author:** ![Moirai](https://avatars.discourse-cdn.com/v4/letter/m/96bed5/32.png) [@Moirai](https://boards.straightdope.com/u/Moirai)\ **Post date:** [December 17, 2003, 4:38am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/13 "2003-12-17T04:38:39Z")
> [@](#): > > \*Originally posted by mangomerlot \* > \*\*My parents told me i was born at 7 months. I was born at 8 pounds though. Is that likely or even possible by any of these calculations? \*\* Depends on your parents. Are you a first-born? Here’s what I mean- In my husband’s family, there has always been a joke about 1st and 2nd babies. They say that first pregnancies can be any length, and subsequent pregnancies are 9 months. In case it’s late where you are, it was probably to cover up marriages caused by pregnancy. If they were serious, holy cow. 8 weeks premature and 8 pounds? You might have killed your mom! 😉 ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [December 17, 2003, 5:01am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/14 "2003-12-17T05:01:19Z")
> [@](#): > > \*Originally posted by EJsGirl \* > **They say that first pregnancies can be any length, and subsequent pregnancies are 9 months.** True. If you count back seven months from your birth and get your parents’ wedding day, odds are somebody is fudging the numbers a bit. Not that it’s that big a deal. I’ve read about some Scandinavian cultures where a couple would live together and _only_ marry if/when the woman’s pregnancy was detected, thus demonstrating the union would be productive. ---
**Author:** ![TheLadyLion](https://avatars.discourse-cdn.com/v4/letter/t/d78d45/32.png) [@TheLadyLion](https://boards.straightdope.com/u/TheLadyLion)\ **Post date:** [December 17, 2003, 6:04am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/15 "2003-12-17T06:04:52Z")
> [@](#): > > \*Originally posted by mangomerlot \* > \*\*My parents told me i was born at 7 months. I was born at 8 pounds though. Is that likely or even possible by any of these calculations? \*\* I don’t know why not. Of course a lot of first-born children were often called “preemies” back in the 50s and 60s, even though they were 9 lb. and 21 inches long! Gee, I wonder why? Actually, when I gave birth to my son, the baby born to the couple across the hall from me on the maternity ward was a whopping 14+ lbs., and he was a term baby. He looked like a bouncing baby watermelon, he was just huge! ---
**Author:** ![Moirai](https://avatars.discourse-cdn.com/v4/letter/m/96bed5/32.png) [@Moirai](https://boards.straightdope.com/u/Moirai)\ **Post date:** [December 18, 2003, 3:31am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/16 "2003-12-18T03:31:07Z")
14 pounds?!? My uterus hurts just thinking about it! 😉 ---
**Author:** ![Bad\_News\_Baboon](https://avatars.discourse-cdn.com/v4/letter/b/5fc32e/32.png) [@Bad\_News\_Baboon](https://boards.straightdope.com/u/Bad_News_Baboon)\ **Post date:** [December 18, 2003, 3:35am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/17 "2003-12-18T03:35:02Z")
> [@](#): > > \*Originally posted by mangomerlot \* > \*\*My parents told me i was born at 7 months. I was born at 8 pounds though. Is that likely or even possible by any of these calculations? \*\* Mothers with gestational diabetes often have larger babies. This may have been her case and she didn’t know it. I don’t think they tested for it in the past. ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [December 18, 2003, 3:35am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/18 "2003-12-18T03:35:31Z")
> [@](#): > > Babies are carried for nine months. Or ten. Care to help two childless writers out? Well, you could practice not splitting the infinitive the next time around. “Babies are carried for nine months. Or ten. Care to help out two childless writers?” 😃 ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [December 18, 2003, 4:51am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/19 "2003-12-18T04:51:36Z")
> [@](#): > > \*Originally posted by Duckster \* > \*\*Well, you could practice not splitting the infinitive the next time around. > > “Babies are carried for nine months. Or ten. Care to help out two childless writers?” > > 😃 \*\* Actually, the sentence was ended in a preposition. Splitting the infinitive would be “Care to, two childless writers, help?” ---
**Author:** ![TheLadyLion](https://avatars.discourse-cdn.com/v4/letter/t/d78d45/32.png) [@TheLadyLion](https://boards.straightdope.com/u/TheLadyLion)\ **Post date:** [December 18, 2003, 6:24am UTC](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475/20 "2003-12-18T06:24:48Z")
> [@](#): > > \*Originally posted by Bryan Ekers \* > \*\*Actually, the sentence was ended in a preposition. > > Splitting the infinitive would be “Care to, two childless writers, help?” \*\* Also popularly known as Yoda-speak. 😃 [Next page](https://boards.straightdope.com/t/babies-are-carried-for-nine-months-or-ten-care-to-help-two-childless-writers-out/218475.md?page=2)