Things Nobody Warns You About in the Third Trimester

Lightning crotch is the unofficial (but very accurate) name for sudden, sharp, shooting pain in the vagina, pelvis, or rectum during the third trimester. It feels exactly like it sounds — a bolt of electrical pain that comes out of nowhere and can literally stop you mid-step.

The cause is usually your baby's head pressing on nerves in the lower part of your uterus and cervix, particularly the pudendal nerve. As your baby drops lower into the pelvis (called lightening or engagement), the pressure on these nerves increases. It can also be triggered by the baby shifting position or kicking.

Lightning crotch is more common when standing, walking, or changing positions. It typically lasts only a few seconds — long enough to make you gasp but not long enough to time. While startling and uncomfortable, it's not harmful to you or the baby. Pelvic support garments, warm baths, and changing positions can help. If the pain is constant rather than fleeting, or comes with regular contractions, contact your provider.

Pregnancy brain is absolutely real — and backed by research. A 2018 meta-analysis published in the Medical Journal of Australia confirmed that pregnant women perform significantly worse on memory and cognitive function tests compared to non-pregnant controls, particularly in the third trimester.

The causes are multifactorial. Hormonal shifts (rising progesterone and estrogen) affect neurotransmitter function. Sleep deprivation — common in the third trimester when finding a comfortable position becomes an Olympic sport — directly impairs short-term memory and executive function. Your brain is also literally restructuring: MRI studies show gray matter volume changes during pregnancy, particularly in areas involved in social cognition (your brain is rewiring to bond with your baby).

Practical coping strategies include using your phone for reminders and lists, putting keys and essentials in the same place every time, giving yourself grace when you forget things, and telling your partner or colleagues what you need. The cognitive fog typically improves within a few months postpartum, though some studies suggest subtle changes can persist for up to two years.

Vivid, bizarre, and sometimes genuinely disturbing dreams are a hallmark of the third trimester, and you're not losing your mind. There are several reasons they intensify near the end of pregnancy.

First, hormonal surges — particularly progesterone — affect REM sleep, the stage where the most vivid dreaming occurs. Second, you're waking up more frequently (thanks to bathroom trips, discomfort, and baby kicks), and waking during REM sleep makes you more likely to remember your dreams. Third, anxiety about labor, parenting, and the life change ahead gives your subconscious plenty of material to work with.

Common third-trimester dream themes include forgetting or losing the baby, giving birth to animals or objects, being unprepared for labor, infidelity or relationship anxiety, and danger or disaster scenarios. These dreams don't predict anything — they're your brain processing a massive life transition.

If nightmares are severe enough to cause significant anxiety or sleep avoidance, mention them to your provider. Occasional unsettling dreams are normal, but persistent, distressing nightmares may benefit from counseling or relaxation techniques before bed.

Feeling short of breath in the third trimester is incredibly common and usually not dangerous. There are two main causes working together against your lungs.

First, your growing uterus pushes your diaphragm upward by about 4 cm (1.5 inches), physically reducing the space your lungs have to expand. Second, progesterone stimulates the respiratory center in your brain to increase your breathing rate, which can make you feel like you're breathing harder even when your oxygen levels are perfectly normal.

Interestingly, even though you feel breathless, your body is actually more efficient at oxygen exchange during pregnancy — you're delivering 20% more oxygen per breath to support the baby. The sensation of breathlessness doesn't mean you or your baby are oxygen-deprived.

Relief strategies include sitting up straight or standing tall to give your lungs more room, sleeping propped up on pillows, taking slow deep breaths, and avoiding overexertion. Many women get some relief in the last few weeks when the baby "drops" lower into the pelvis, taking pressure off the diaphragm. If breathlessness is sudden, severe, or accompanied by chest pain, rapid heart rate, or bluish lips, seek emergency care — these could indicate a pulmonary embolism or cardiac issue.

If you feel like you live in the bathroom, you're in good company. Frequent urination in the third trimester is driven by your baby's head pressing directly on your bladder, reducing its capacity from roughly 16 ounces to sometimes as little as a few tablespoons. Add to that increased blood volume (your kidneys are filtering 50% more blood than before pregnancy) and you have a recipe for constant bathroom trips.

Peeing 10-13 times per day is within the range of normal for the third trimester, including 2-4 times per night. Some women also experience stress incontinence — leaking a little when they laugh, cough, sneeze, or stand up. This affects up to 40% of pregnant women and is caused by the weight of the uterus weakening pelvic floor muscles.

Don't reduce your water intake to pee less — staying hydrated is critical for amniotic fluid levels, blood volume, and preventing urinary tract infections (which are more common in pregnancy). Instead, try leaning forward when you pee to empty your bladder more completely, doing Kegel exercises to strengthen your pelvic floor, and front-loading fluids earlier in the day while tapering in the evening.

Round ligament pain is a sharp, jabbing, or pulling sensation in the lower belly or groin — usually on the right side — caused by the thick ligaments that support your uterus stretching as it grows. It's one of the most common complaints in pregnancy, particularly during the second and third trimesters.

It's distinctly different from contractions. Round ligament pain is sudden and triggered by movement (standing up quickly, rolling over in bed, laughing, coughing, or sneezing), lasts only a few seconds to a minute, is localized to one or both sides of the lower abdomen, and stops when you rest or change position. Contractions, by contrast, involve the entire uterus tightening, last 30-60+ seconds, and come in a pattern.

Relief strategies include moving slowly when changing positions (especially getting out of bed), flexing your hips before coughing or sneezing, wearing a maternity support belt, warm compresses on the painful area, and gentle stretching. If the pain is persistent, worsening, or accompanied by fever, bleeding, or contractions, call your provider to rule out other causes.

Third-trimester insomnia affects up to 75% of pregnant women, so if you're staring at the ceiling at 3 AM, you're far from alone. The causes stack up: physical discomfort, frequent urination, heartburn, restless legs, anxiety about labor, vivid dreams that wake you, and the frustrating irony of being exhausted but unable to sleep.

Your body is also preparing for the sleep disruption of newborn care — some researchers theorize that third-trimester insomnia is an evolutionary adaptation, though that's cold comfort at 4 AM.

Evidence-based strategies include maintaining a consistent sleep schedule, keeping the room cool and dark, using a pregnancy pillow for support, limiting screen time before bed, trying relaxation techniques like progressive muscle relaxation or guided meditation, and a light protein-rich snack before bed (to prevent hunger-related wakeups). Avoid sleep aids unless specifically approved by your provider — most over-the-counter options aren't recommended during pregnancy.

If you're getting fewer than 5 hours per night consistently, tell your provider. Severe insomnia in the third trimester has been linked to longer labor and higher rates of C-section, so addressing it matters for your birth experience too.