Quando a bebê tiver sono, eu vou pegá-la no colo.

Because after quando when you are talking about a future situation, Portuguese normally uses the future subjunctive.

So:

• Quando a bebê tiver sono... = When the baby gets/is sleepy...
• not Quando a bebê tem sono... if you mean a future moment
• not usually Quando a bebê terá sono...

This is a very common pattern in Portuguese:

• Quando eu chegar, ligo para você.
• Quando ele puder, ele vai ajudar.
• Quando eles saírem, nós vamos entrar.

For English speakers, this can feel strange because English usually uses the present in this kind of clause: When the baby is sleepy... But Portuguese uses the future subjunctive here.

Bebê can be used with either o or a, depending on the sex of the baby.

• o bebê = the baby boy / the baby
• a bebê = the baby girl

In this sentence, a bebê tells you the baby is female, which also matches the pronoun later: pegá-la = pick her up.

You may also hear o bebê used generically in some situations, but a bebê is completely normal when referring to a girl.

Ter sono means to be sleepy or to feel sleepy.

Literally, it is to have sleep, but that is not how we say it in natural English. It is just the Portuguese way of expressing sleepiness.

Examples:

• Estou com sono. = I’m sleepy.
• Tenho sono à tarde. = I get sleepy in the afternoon.
• Quando a bebê tiver sono... = When the baby is sleepy / gets sleepy...

A very common alternative in Brazilian Portuguese is estar com sono:

• Quando a bebê estiver com sono...

That version is also very natural.

Eu vou pegar is the very common spoken way to express the future in Brazilian Portuguese.

So:

• eu vou pegar = I’m going to pick up / I will pick up
• pegarei = I will pick up

Both are grammatical, but vou + infinitive is usually more natural in everyday speech.

This is similar to English, where I’m going to pick her up often sounds more natural than I shall/will pick her up.

Pegá-la means to pick her up or to take/hold her.

It is made of:

• pegar = to take, get, pick up
• la = her

In standard written Portuguese, object pronouns like o, a, os, as can attach to the verb with a hyphen:

• pegar + a → pegá-la

The r at the end of pegar drops, and the pronoun becomes la. The written accent in pegá-la helps show the stress.

Similar examples:

• amá-lo = to love him
• vê-la = to see her
• comprá-lo = to buy it/him

Yes, in everyday spoken Brazilian Portuguese, many people would say vou pegar ela no colo.

That is very common in conversation.

However:

• vou pegá-la no colo sounds more standard and formal in writing
• vou pegar ela no colo sounds more colloquial and spoken

So if you are learning textbook or formal Portuguese, pegá-la is the form to know. If you are listening to real Brazilian speech, pegar ela is also very common.

No colo is an idiomatic expression that usually means in one’s arms or held against one’s body, especially when talking about a baby or small child.

So pegar a bebê no colo means something like:

• pick up the baby and hold her in your arms
• take the baby in your arms

Literally:

• colo refers to the area of the lap/chest/arms where you hold a child
• no = em + o

Even though colo can sometimes be translated as lap, in this expression pegar no colo often means more than just putting someone on your lap. It often means lifting and holding the child affectionately.

Because colo is a masculine noun: o colo.

So:

• em + o = no
• em + a = na

That is why the sentence has no colo.

Other examples of the same contraction:

• no carro = in the car
• na casa = in the house
• no quarto = in the bedroom
• na escola = at school

Because the sentence begins with a subordinate clause:

• Quando a bebê tiver sono = When the baby is sleepy
• eu vou pegá-la no colo = I’m going to pick her up

In Portuguese, when this kind of time clause comes first, a comma is normally used before the main clause.

So the structure is:

• Quando... , eu vou...

If you reverse the order, the comma is often not needed:

• Eu vou pegá-la no colo quando a bebê tiver sono.

Not strictly. Portuguese often drops subject pronouns when the verb already makes the subject clear.

So both are possible:

• Quando a bebê tiver sono, eu vou pegá-la no colo.
• Quando a bebê tiver sono, vou pegá-la no colo.

Both mean the same thing.

Including eu can add a little emphasis or clarity, but it is not required.

It can suggest either one, depending on context.

In natural English, this sentence could be understood as:

• When the baby is sleepy, I’ll pick her up
• When the baby gets sleepy, I’ll pick her up

Portuguese does not always force that distinction here. The important idea is that at the future moment when the baby feels sleepy, the speaker will pick her up.

So the Portuguese structure is broader than a word-for-word English gloss might suggest.