The Playbook

13 Weeks Pregnant: The Last Week of the First Trimester

By the Guide to Fatherhood editorial team. Last reviewed . 2 min read.

Checked against guidance from organizations like the AAP, CDC, ACOG and NHS (linked below). This is general information, not medical advice. Read our medical disclaimer.

Trimester1
Sizea lemon
Length / weightabout 2.9 in (7.4 cm), about 0.8 oz (23 g)

Fingerprints are forming on tiny fingertips, vocal cords are developing, and the intestines are moving from the umbilical cord into the abdomen.

Your to-do list this week

  • Decide when and how you'll tell your own manager. You don't need to share details, but early notice helps leave planning.
  • If she's feeling better, start a weekly walk together. It's good for both of you and becomes a ritual.
  • Write down three things you want to have done by the end of the second trimester. Put them in a shared list.
  • Thank her, specifically, for getting through the first trimester. It was hard.
A conversation to have this week

"What do you want the second trimester to feel like?" More rest? A trip? Nursery planning? Time with friends? Plan for it on purpose.

The baby this week

About the size of a lemon, the baby is growing quickly. Fingerprints are forming, vocal cords are developing, and the intestines, which grew partly inside the umbilical cord, are settling into the abdomen (Mayo Clinic). In the UK, NHS guidance starts the second trimester this week (NHS); in the U.S., ACOG counts it from 14 weeks. Either way, you’re nearly through the hardest stretch for a lot of people.

How she may be feeling

Often better. Energy can creep back and nausea can ease, though there’s wide variation. Her body is visibly changing for many people around now, and that can bring a mix of excitement and self-consciousness. Follow her lead on bump talk.

Telling work

Your partner’s announcement at her job is her decision. Yours is simpler, but timing still matters for leave:

  • Read the policy first so you know what to ask for.
  • Tell your manager in person (or on a call), with a rough timeline: “We’re due in [month]. I’m planning to take parental leave and will have dates to you by [date].”
  • Don’t over-promise availability during leave. “I’ll check email” turns into working from the hospital. See how to ask for paternity leave.

Under FMLA, employees generally must give 30 days’ notice when leave is foreseeable, so earlier conversations are your friend.

Build a second-trimester rhythm

The middle trimester is the best window for getting things done and enjoying each other before the baby arrives. Start small habits now:

  • A weekly walk. ACOG recommends regular moderate exercise during an uncomplicated pregnancy, about 150 minutes a week. Walking together counts and doubles as your best talking time.
  • A shared to-do list with no more than three items per trimester. Nursery basics, leave paperwork, a childbirth class.
  • Date nights while sleep is still an option.

Frequently asked questions

When should I tell my employer we're expecting?

There is no legal deadline for a partner to tell an employer. Many dads share the news after the first trimester and give formal notice for leave once they know the policy, often 30 or more days before leave starts (FMLA generally requires 30 days' notice when the need is foreseeable).

Sources

  1. Week 13: Your baby and your body, NHS
  2. Fetal development: The first trimester, Mayo Clinic
  3. Exercise During Pregnancy, American College of Obstetricians and Gynecologists

We link to the original source for every medical and safety claim. Guidance changes; if a source has been updated since our last review, the source wins. How we research.