Moja trudna supruga čeka u bolnici.

Because supruga is a feminine singular noun, and the possessive adjective moj must agree with it in gender, number, and case.

So:

• moj = masculine singular
• moja = feminine singular
• moje = neuter singular

Since supruga means wife and is feminine, you say moja supruga = my wife.

For the same reason: trudna is an adjective, and adjectives in Croatian must agree with the noun they describe.

Here, trudna describes supruga, so it has to match:

• feminine
• singular
• nominative

That is why you get trudna supruga = pregnant wife.

Compare:

• trudan muž = a pregnant husband (grammatically masculine, even if semantically odd)
• trudna supruga = a pregnant wife
• trudno dijete = a pregnant child (again, just to show grammar)

It is in the nominative singular because it is the subject of the sentence.

The subject is the person doing the action of čeka.

So in:

• Moja trudna supruga čeka u bolnici.

the subject is moja trudna supruga.

Dictionary form:

• supruga = wife

Nominative is also the form you usually see in vocabulary lists.

Because the preposition u often requires the locative case when it means in or at a place.

Here the sentence describes location, not movement:

• u bolnici = in / at the hospital

The noun changes like this:

• nominative: bolnica
• locative: bolnici

So:

• bolnica = hospital
• u bolnici = in the hospital / at the hospital

If there were movement into the hospital, Croatian would often use u + accusative instead.

It can mean both, depending on context.

Croatian present tense often covers both the English simple present and present continuous:

• čeka = waits / is waiting

In this sentence, English would most naturally translate it as is waiting, but grammatically Croatian does not need a separate form like English does.

The verb is:

• infinitive: čekati = to wait
• čeka = he/she/it waits, is waiting

Since the subject is supruga, it means she is waiting.

It is 3rd person singular present tense.

That form is used with:

• on = he
• ona = she
• ono = it

So:

• ja čekam = I wait / am waiting
• ti čekaš = you wait / are waiting
• on/ona/ono čeka = he/she/it waits / is waiting

Because moja trudna supruga is a singular subject, the verb must also be singular: čeka.

Because Croatian does not have articles like English a and the.

So supruga can mean:

• wife
• a wife
• the wife

The exact meaning depends on context.

In this sentence, moja already makes the meaning specific, so moja trudna supruga naturally means my pregnant wife.

Croatian word order is fairly flexible, because endings show grammatical relationships. But some orders sound more natural than others.

The neutral order here is:

• Moja trudna supruga čeka u bolnici.

You could also hear variations such as:

• U bolnici čeka moja trudna supruga.
• Moja supruga čeka u bolnici.

Changing the order usually changes focus or emphasis, not the basic meaning.

In ordinary speech, the original sentence sounds natural and straightforward.

It can correspond to either in the hospital or at the hospital in English, depending on context.

Croatian u bolnici literally means in the hospital, but English sometimes prefers at the hospital when speaking more generally about location.

So this phrase can be understood as:

• physically inside the hospital
• located there in general

Context tells you which nuance is intended.

Yes. Supruga is a standard and very common word for wife.

A few notes:

• supruga = wife
• suprug = husband

You may also hear žena, which can mean woman or wife, depending on context. But supruga is more precise, because it specifically means wife.

So:

• moja žena can mean my wife
• moja supruga definitely means my wife

That is the normal position for these kinds of modifiers in Croatian.

Before the noun, you commonly place:

• possessives: moja
• descriptive adjectives: trudna

So:

• moja trudna supruga

is the natural equivalent of my pregnant wife.

Croatian can sometimes place adjectives after the noun in special styles or fixed expressions, but for everyday neutral speech, moja trudna supruga is exactly what a learner should expect.