Third Trimester Surprises — What Partners Aren't Told

Lightning crotch is exactly what it sounds like — sudden, sharp, shooting pain in the pelvis, vagina, or rectum that hits like an electric shock and disappears just as fast. It typically lasts only a few seconds but can be so intense that she gasps, stops mid-sentence, or grabs onto something.

This is caused by the baby's head (or other body parts) pressing on nerves in the lower pelvis, particularly as the baby drops lower in the third trimester. It can also be triggered by the baby's movements hitting the cervix or by the stretching of the round ligaments that support the uterus. It's completely harmless — but it doesn't feel harmless.

Lightning crotch tends to happen more frequently as the baby engages (drops into the pelvis in preparation for birth), which is why it's most common in the last 4-6 weeks. It can strike when she's walking, standing up, changing positions, or doing absolutely nothing.

The reason you need to know about this: when your partner suddenly winces, clutches her pelvis, and says something like "oh my GOD" in the middle of Target, your first instinct may be to panic. Knowing that lightning crotch exists — and that it's normal — keeps you from rushing to the ER for what is essentially a very unpleasant but benign nerve zap.

That said, if the sharp pain doesn't go away, is constant rather than fleeting, or is accompanied by bleeding or contractions, that's different. Persistent pelvic pain warrants a call to the provider.

Yes, pregnancy brain is scientifically real, and it's not her being careless or lazy. Research published in the Medical Journal of Australia and confirmed by multiple neuroimaging studies has shown that pregnancy causes measurable changes in brain structure and function.

During the third trimester, gray matter volume actually decreases in areas associated with social cognition — the brain is literally reorganizing itself for parenthood. Combine that with hormonal surges (progesterone has sedating effects on the brain), chronic sleep disruption (she's up 3-5 times a night to pee), physical discomfort that makes concentration difficult, and the massive cognitive load of preparing for a baby.

The result: she forgets words mid-sentence, walks into rooms with no idea why, loses her keys daily, struggles with tasks she'd normally breeze through, and may feel genuinely frustrated or frightened by the cognitive fog. Some women describe it as feeling like they're thinking through syrup.

This is particularly hard for women who pride themselves on being sharp and organized. The loss of cognitive function can feel alarming and even humiliating. When she says "I feel so stupid," she's not fishing for compliments — she's expressing genuine distress about a change she can't control.

The good news: the brain changes largely reverse after delivery (though sleep deprivation with a newborn doesn't help). In the meantime, small practical supports make a real difference.

By the third trimester, the uterus has grown to the point where it's physically pushing up against the diaphragm — the muscle that powers breathing. This reduces her lung capacity by up to 20%, meaning every breath is shallower than normal. She's literally breathing for two with less room to do it.

On top of the mechanical compression, progesterone (the dominant hormone of pregnancy) actually changes her breathing pattern. It increases respiratory rate and sensitivity to carbon dioxide, which can create a sensation of breathlessness or air hunger even when her oxygen levels are completely normal.

The result: she gets winded climbing stairs, can't finish a sentence without pausing to breathe, feels short of breath lying flat (especially on her back), and may wake up gasping at night. She might need to sleep propped up on pillows or in a reclined position.

This usually improves in the last 2-4 weeks of pregnancy when the baby drops into the pelvis (called lightening), which takes pressure off the diaphragm. Until then, it's a daily struggle that's invisible to everyone except her.

When to be concerned: if breathlessness comes on suddenly, is severe, is accompanied by chest pain, a racing heart, coughing up blood, or swelling in one leg, these could be signs of a pulmonary embolism (blood clot in the lung) — a rare but serious pregnancy complication. Call 911 for sudden-onset severe breathlessness with any of those accompanying symptoms.

No — and suggesting she reduce fluids is genuinely harmful. Dehydration during pregnancy increases the risk of urinary tract infections, preterm contractions, and constipation. She needs to drink more water in the third trimester, not less.

Here's why she's peeing constantly: the baby's head is sitting directly on her bladder. In the third trimester, the uterus takes up so much room in the pelvis that the bladder is compressed to a fraction of its normal capacity. She physically cannot hold as much urine as she used to — sometimes as little as a few tablespoons triggers the urge to go.

On top of that, her kidneys are filtering 50% more blood volume than before pregnancy, producing more urine. And the baby's movements can press against the bladder without warning, creating sudden urgency that she can't ignore.

At night, this becomes a particular nightmare. When she lies down, fluid that's been pooling in her swollen legs and feet (thanks to gravity) returns to her bloodstream and gets filtered by her kidneys, causing increased nighttime urination. This means even if she stops drinking water at 8 PM, she'll still be up multiple times.

The sleep disruption from this alone is significant. She may be getting up 4-8 times per night, and each trip involves the physical effort of rolling her pregnant body out of bed, navigating to the bathroom in the dark, and trying to fall back asleep. It's exhausting.

The third trimester is a greatest-hits album of discomfort, and many symptoms overlap and compound each other. Here's what else she may be dealing with — and what you should know about each.

Rib pain and rib flaring: the uterus pushes the ribs outward, and the baby's feet may kick against them directly. Some women feel like their ribs are being pried apart. There's no treatment — just endurance.

Swelling (edema): mild swelling in the feet, ankles, and hands is normal due to increased blood volume and fluid retention. Sudden severe swelling (especially in the face) is a preeclampsia warning sign — report it immediately.

Insomnia: between the peeing, the heartburn, the inability to find a comfortable position, the baby doing acrobatics at 2 AM, and the anxiety about becoming a parent — sleep becomes almost impossible. This is not a willpower problem.

Heartburn and acid reflux: progesterone relaxes the valve between the stomach and esophagus, and the uterus pushes the stomach upward. She may not be able to eat a full meal without feeling like her chest is on fire. Smaller, more frequent meals help.

Pelvic girdle pain (PGP): the hormone relaxin loosens the joints in her pelvis to prepare for birth. This can cause stabbing pain in the pubic bone, hips, and lower back, especially when walking, turning over in bed, or climbing stairs. Some women need a support belt or physical therapy.

Carpal tunnel syndrome: yes, really. Fluid retention during pregnancy can compress the nerves in the wrists, causing numbness, tingling, and pain in the hands. It usually resolves after delivery.

None of these are "just part of pregnancy" in the sense that she should silently endure them. They're all worth discussing with her provider, especially if any symptom significantly impacts her daily life.