Co-parenting is a partnership built for 18-plus years of joint decisions, often without the foundation of trust and shared history that married couples have. Conflict isn't the exception here — it's the statistical norm: most co-parents end up articulating their expectations of each other only after the fact, once the pregnancy is confirmed and every assumption that once seemed obvious suddenly becomes a point of dispute.
Spouses' disagreements usually rest on shared history: even when a couple argues about money or parenting style, each partner has a rough sense of how the other reacts under stress, built up over years of shared daily life. Co-parents who came together specifically to have a child don't have that history — sometimes they've known each other for only a few months before conception. Any assumption about 'how things should be,' which in a marriage would have sorted itself out through thousands of small everyday moments, has to be spelled out loud for co-parents — and often that happens for the first time only once the pregnancy is already underway and the emotional cost of getting it wrong has gone up.
Most conflicts fall into a handful of recurring themes — and almost always, the issue isn't the topic itself, but the fact that the two sides' assumptions about it never matched in the first place.
Look closely, and almost every one of these isn't really a disagreement about the child at all — it's a difference in unspoken expectations that neither co-parent ever said out loud before conception, simply because it didn't occur to them that it needed a separate conversation.
The topics of disagreement don't change much from the start of the pregnancy to the end, but their emotional weight and urgency change a great deal — and that's worth factoring in when deciding when and how to raise difficult questions.
First trimester: anxiety and untested assumptions
The early weeks are when the pregnancy usually isn't widely announced yet, prenatal-testing decisions come up for the first time, and both co-parents' anxiety about the outcome tends to run higher than either is willing to admit. Conflicts here are mostly about the amount of information shared: who gets updates on how things are going and how often, whether to announce the pregnancy earlier or later than the standard 12-week mark, who decides on the first expanded screening.
Second trimester: roles stop being abstract
By the middle of the pregnancy, vague agreements like 'we'll figure it out as we go' stop working, because real planning is needed: an appointment schedule, a delivery budget, a conversation with employers, sometimes a move to give birth in a particular country or clinic. This is usually when disagreements about money and about new romantic partners' roles surface most often, because it becomes clear that agreements will have to be honoured in practice, not just discussed in theory.
Third trimester: birth logistics and control over uncertainty
As the birth approaches, conflicts concentrate around one question: who decides what if things don't go according to plan. The birth plan, who's in the delivery room, emergency medical decisions — topics that many co-parents put off until the last possible moment, even though it's precisely the stress of labour that makes the absence of a clear agreement most painful.
One of the most practical tools to borrow from negotiation practice is the distinction between position and interest that Fisher and Ury championed. A position is what someone demands out loud: 'I want to be at every doctor's appointment.' An interest is what's behind that demand — for instance, fear of missing important information about the child's health, or a feeling of being excluded from the process. As long as the conversation stays at the level of positions, agreement is almost impossible — someone has to 'give in.' Once the conversation moves to the level of interests, there are usually several solutions available, and not all of them require being at every single appointment.
Step 1. State the position without arguing
One co-parent says what they want, while the other listens without objecting or asking clarifying questions at this stage — the goal isn't to evaluate the demand, just to register it.
Step 2. Find the interest behind the position
Partners take turns answering the question 'what actually matters to me here, if you strip away the specific form of the demand' — almost always, it turns out the real issue isn't control, but anxiety, information, or a sense of being included.
Step 3. Generate options not tied to the original positions
At this stage, both sides come up with several ways to address both interests at once — for example, shared access to the medical record and a photo update after every appointment instead of being physically present at all of them.
Step 4. Choose a solution based on an objective standard
The final choice is made not based on who pushed harder, but on an external reference point — a doctor's recommendation, a work schedule, a budget. This reduces the sense that one co-parent 'won' and the other 'lost' — and that feeling is usually exactly what poisons future cooperation.
Turning a position into an interest is easier with an example in hand. Here are three situations from the table above and what the conversation can sound like when you move from a demand to the interest behind it, rather than the other way around.
These roles solve different problems, and co-parents often confuse them, turning to the wrong specialist for the wrong situation.
It's worth going to a mediator earlier than feels necessary — before the conflict has had a chance to repeat several times and settle in as a familiar communication pattern. It makes sense to involve a lawyer in parallel with the medical protocol, not after the child is born, once some decisions have already been made in practice but never formalised.
Not every disagreement points to deep incompatibility, but there are a few recurring patterns worth noticing sooner rather than later.
None of these patterns on its own is a reason to end the arrangement, but each is a reason to bring in a mediator as early as possible — or, if the situation allows, to openly discuss whether both sides are actually ready for 18 years of joint decisions made in this particular communication style.
Most of the items below don't need an immediate answer — they need an answer to exist before circumstances force one to be made in a hurry.
Medical decisions
Money
Social circle
Birth
Documents and legal status
The negotiators the Fisher-and-Ury method was designed for always had a fallback: simply not signing the deal and walking away. Co-parents who have already chosen this path together don't have that fallback in the same sense — the child will arrive either way. What's still genuinely theirs to choose is the quality of the relationship between the child's parents for the next 18 years, and that's something best decided deliberately, in advance, rather than sorted out after the fact.