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Day 79 of 280 · 11 weeks + 2 days

Running hot

Last reviewed · 3 min read · 5 sources · Plain-text version

More blood means more heat. Why you sweat and feel dizzy at eleven weeks, and the cool-down kit to carry so a warm day doesn't flatten you.

Size this week
about the size of a fig
Length this week
around 41 mm from head to bottom
An East Asian woman in a loose linen shirt resting on a shaded park bench on a bright summer day, a water bottle in hand, her friend beside her holding two iced drinks.

Eleven weeks and two days. If you've been peeling off layers while everyone else is comfortable, that's the extra blood. Today you build a small kit for it.

Your baby

A single purple fig on a plain pale wooden table, soft window light.

Around 41mm long from head to bottom, about the size of a fig, with tiny nails and ears forming (NHS). The baby is not what's making you hot. You are: the body is working harder to cool both of you (CDC).

Your body

Higher blood volume can cause heat, sweating and dizziness, and rest is important (NHS). The volume will increase by up to 50% over the pregnancy, which can also make you thirsty; the NHS suggests about eight medium glasses of fluid a day (NHS).

The CDC's page on heat is blunt about why it matters. Pregnancy can make a person more likely to get sick when it is very hot, and heat exhaustion or heat stroke can come on sooner because the body has to cool both the pregnant person and the baby (CDC). Pregnancy also raises the risk of dehydration, which reduces the body's ability to cool itself through sweat (CDC). Two lines to act on: "Create a heat action plan with your doctor," and if you're sweating heavily, ask your doctor how to replace the salt and minerals safely (CDC).

Try today

  1. The cool-down kit

    Time: 10 minutes

    1. Fill a water bottle and leave it by the door, so it's the thing you pick up with your keys. Dehydration is what makes heat dangerous faster in pregnancy (CDC).

    2. Add a small folding fan or a cloth you can wet, and a hat.

    3. Walk your usual route in your head and mark one shady stop where you can sit; rest is the NHS's answer to the heat and dizziness (NHS).

    4. On a hot day, check the CDC HeatRisk forecast for your zip code before you plan anything outdoors (CDC).

    Make it work:

    If you sweat heavily most days, put "how do I replace salt and minerals?" on the list for your next visit instead of guessing with sports drinks (CDC).

Watch for

  • Normal

    feeling hot and sweaty with everyone else in a jacket (NHS).

    Go to the ER

    for symptoms of heat-related illness; the CDC says to seek medical care immediately (CDC).

  • Normal

    feeling warm after a walk.

    Call your provider

    for a fever of 100.4°F (38°C) or higher (CDC).

  • Normal

    a moment of lightheadedness when you stand up quickly, because blood pressure tends to run lower (NHS).

    Call your provider

    for dizziness or fainting (CDC).

For you

The CDC's rule for hot days is short: "Do not engage in very strenuous activities and get plenty of rest" (CDC). The reason is stated once on the same page: in very hot environments or during strenuous activity your core temperature can rise, and in some cases higher internal temperature and fever during pregnancy have been linked to birth defects and other complications (CDC). That is a reason to plan, not to panic. A bottle, a hat and a bench cover most of it.

If you're the partner: carry the water. On a hot day, you're the one who notices she's gone quiet and steers for the shade.

Sources

This guide is general education that summarizes published research and guidance from groups like the American Academy of Pediatrics, the CDC, and the WHO. It isn’t medical advice, and every child develops on their own timeline. Your pediatrician knows your child; if something feels wrong, call them. In an emergency, call 911.

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