Can I book an International future flight for my not yet born daughter?

Could someone with airline knowledge help me out here? I've tried calling the airline but I can't get a straight answer and google doesn't help. I'm looking to book a flight from Los Angeles to London for May 2020. My second daughter isn't going to be born until December this year. I want to book now because I want to buy her a seat and reserve them all near each other and not do the lap thing. If I book later I'm afraid I won't be able to get 4 seats for the kids and us next to each other. The only issue I'm having is when I go to purchase the tickets it asks me for her date of birth and won't let me choose a later date. I obviously can't predict her birth date, I figured I would just put her expected date but that doesn't work. So, is there any way to book a flight and a seat for her before she's born? Or is there no way around it? I don't want to make up a birth date because I'm afraid if her reserved information doesn't match her passport, it'll be trouble.

Honestly, you shouldn't book a flight that early.

You can fool the system. Book one seat as fully refundable full fare planning to cancel it and adding a 5 month old in special air capable seat for infants whether bring your own or working with the airline. Under a year old in a separate seat normally has a heavy discount. They'll probably be annoyed, but you should be able to get what you want. Airfares now will often be higher than booking in December for May, but you do what you want to do. You'll need to work directly with customer service about the cancel and rebook and refunding. They must put a name and date of birth on any reserved seat for security reasons. You can't book a seat without it, but you can make up a name and birth date as passenger and cancel if buying a non-discounted seat. You don't need proof until check-in.

I would think you can simply book two tickets for yourself (just say you want the space if questioned - the space could be for a valuable instruments, you need it for your size or whatever you want to tell them). Apparently that ticket may possible be cheaper because you make get out of paying taxes on the 2nd seat.

Since the child will be that young they will be a lap child and then you can just put them in that seat.

But, that being said apparently international these days can be a bit complicated with "lap children" and what they charge you to bring the child but that wouldn't really affect the seat in most scenarios.

It is sad that it is this complicated. We took a child internationally at 12 weeks old and the only tricky part was making sure to get a passport as soon as we got a birth certificate.

Of course YOU do not know how to use the Airline booking site for a non standard booking.
Suggest you try using the HUMAN at the Airline to assist you.

The Airline has a way to do it. YOU DO NOT need to know how they do it.

The AIRLINE booking agent knows how it is done is all you need to know.

Your booking is incomplete until child is born and you can add the appropriate details at that time to the booking.

The computer booking sites are not set up for this. The Airline reservations HUMANS have a work around to deal with the situation.

Wait until your child is born before booking. You really don't need to book so soon. Seats are available when you book closer to the date you're leaving. They really are. I know these things, because I'm a frequent traveler and sometimes I travel with a number of other people where we all get to sit next to one another.

I don't understand why people are so reluctant to pick up their phones and CALL someone in the airline to explain the situation and ask for their advice.

Online booking forms are standardised; they aren't designed for unusual situations like this. Rather than trying to cheat the system, just CALL and speak to a human being.

You won't have any problems booking four seats together in December or January for a trip to London in May. Just wait until your daughter is born and get her passport so you know both her DoB and her passport number when you book the tickets.

You can't book a flight for someone that isn't born yet.

There are 2 ways to go about this. The first way is to wait until after she is born. That way you have the passenger's name unless you already have the baby's name picked out. But I think it will be hard for the airline to sell a ticket to a person not yet born. Another option is to see instead of buying your baby a seat, getting a seat where there may be a bassinet. Some of the international flights have these and they are in the bulkhead rows. You can ask the airline you are flying on if they have this option. Again I think it is best to wait until after the baby is born to buy the tickets.