The stomach is a digestive organ and is totally different from the uterus.
Women do not carry babies in their stomachs unless they are cannibals (eating babies).
When women are pregnant, they carry a child in their womb or uterus .
You will, however, regularly hear people say that a woman's belly grows when they are pregnant, or that there is a baby " in their belly ".
And the word " belly " is sometimes used in a manner that is synonymous with " stomach ", while at other times it refers to the external area of the body outside of the stomach.
But " stomach " is generally used to refer specifically to the internal digestive organ, and it would sound a bit strange to say that a woman " has a baby in her stomach " ...
although you'd still be clearly understood by almost any English speaker.
ell.stackexchange.com/users/42872/J. Taylor
Informally, 'stomach' (and the informal form of the word 'tummy') can refer to the abdomen as a whole - when someone is said to have a 'flat stomach', 'hard stomach' or 'distended stomach' then it takes the wider meaning.
Examples talking about 'stomach' in pregnancy can be found '
Generally, you expect a hard stomach when you’re pregnant. ' or 'Of course your stomach won't go back to pre-pregnancy size right away'
But generally you wouldn't use this meaning with 'in the stomach'
as, while it would be understood, it could be ambiguous:
Cartoon source
ell.stackexchange.com/users/9024/Pete Kirkham
Stomach is used specifically to describe a place where food is digested, so it's not very useful for a baby.
I'd use belly as a generic term instead:
She has a baby in her belly
Womb and uterus would also be okay, but these words are more "medical".
ell.stackexchange.com/users/2127/CowperKettle
It depends on whether you are speaking to an adult (who has a larger, more precise vocabulary) or a young child (whose vocabulary is limited and when accuracy does not matter as much).
Most speakers would use "pregnant", unless the other person doesn't know the word.
"She is pregnant."
The most accurate and shortest way to say it, and the most common expression between adults.
"
She has a baby in her abdomen."
Uses the proper scientific term, but rarely used.
"
She has a baby in her belly."
Occasionally said to both adults and children.
"
She has a baby in her tummy."
Much more likely to be said to or by a child than an adult.
"
She has a baby in her stomach."
Anatomically wrong, but still very commonly said to or by a child, often because they already know the word "stomach".
Such a child would probably also know "tummy" or "belly", so it's not clear why this expression continues to be used.
ell.stackexchange.com/users/77799/DrSheldon
If your goal is to speak like a native speaker, then you would say "she is pregnant" or "she is expecting (a baby.)
" You would not say "a baby in her stomach" as that is wrong enough to sound odd because it is the right area but the wrong organ.
You likewise would not have to say "a baby in her uterus" because that is the natural location for a baby and anything else would be so unusual and even outlandish that it just wouldn't come up except in a medical context.
The words belly and tummy are colloquial terms that people use for the area on the front of the body between the hips and chest.
Belly is commonly used by adults and tummy by children or adults speaking to children.
You could say "baby in her belly" but that is kind of crude and not used in formal speech or even polite company.
However, it is perfectly acceptable to say "a baby in her tummy" when speaking to children.
ell.stackexchange.com/users/90888/David
Stomach or gaster is a part of digestive system, not of reproductive system.
If woman had successful fertilization, we would use the term "pregnant".
The "baby in ones belly" would be in use when there are visible signs of pregnancy, let's say after 16 weeks of being pregnant.
ell.stackexchange.com/users/14060/Ilan
Personally, I don't think many people refer to any part of the body when talking about a pregnant person, you could say: 'expecting' 'carrying' or 'carrying a baby' 'pregnant' 'with child' 'up the duff' Although the last one should be reserved for your friends only, remember expectant women can be touchy about everything
ell.stackexchange.com/users/89732/Chris Percival
If a lady is pregnant, for her can this be said?   She had a baby in her  stomach .   Or is it necessary to use the word  womb  or  uterus ?
Difference between 'stomach' and 'uterus'
ell.stackexchange.com
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ell.stackexchange.com/questions/199128
ell.stackexchange.com/users/67723/Zeeshan Siddiqii
Women do not carry babies in their  stomachs, they carry a child in their  womb  or  uterus .  You will, however, regularly hear people say that a woman's  belly  grows when they are pregnant, or that there is a baby " in their belly ". This is much more likely to be said to or by a child than an adult, and most speakers would use "pregnant". The expression "She had a baby in her stomach" is used more for children and although the terms "womb" and "uterus" are used they are used more in medicine. It is most important to note, however, that the most widely used term is "pregnant". 
The expression "She had a baby in her stomach" is used more for children. The terms "womb" and "uterus" are used more in medicine. The most widely used term is "pregnant". 