Week 28: Third Trimester Begins, RhoGAM and Kick Counts

Week 28 is the start of the third trimester. Most weekly updates spend a sentence on the trimester transition and move on, but this week earns the attention. Three real things change. The visits to your provider go from monthly to every two weeks. The standard 28-week prenatal includes a meaningful test or shot for almost every patient. And the way fetal movement is monitored shifts from "trust your instincts" to a formal count.

The baby is now 14¼ inches long and weighs 2½ pounds, about the length of a head of romaine and the weight of a large coconut. From here to delivery, the baby will roughly triple its body weight.

This week

The third trimester begins this week. The NHS marks the threshold cleanly: "Welcome to the 3rd and final trimester!" The transition is more practical than physiological, your prenatal cadence accelerates, your test schedule shifts, and the calendar between you and delivery gets short.

The most important developmental change this week is positioning. Cleveland Clinic notes that "the fetus may begin turning head-down in your uterus as it gets ready for birth" somewhere around now. Most babies will eventually settle head-down by week 36; many do it weeks earlier. Some babies will spend the entire third trimester rotating from breech to head-down and back again before committing. There is no need to worry about the orientation until week 35 or 36, what your provider charts at the week-28 visit is a snapshot, not a prediction.

The baby's brain this week is also visibly more complex. The APA notes that the brain "begins developing as a more complex organ" with visible grooves on the surface and increased brain tissue. The eyebrows and eyelashes are now visible. The hair on the head continues to grow. If you saw a 4D scan this week, the baby would look unmistakably like the baby it is about to be.

The NHS notes that the heart rate has slowed to around 140 bpm and will continue to slow to about 130 bpm at birth, a steady decline from the early-pregnancy peak of 170 or so. The slowing heart is a sign of an autonomic nervous system maturing.

What's happening in your body

The APA places the top of your uterus this week "well above your belly button, about 3 ½ inches (8.9 cm) or more" above the navel. Your fundal height should be around 28 centimeters, plus or minus the standard two-centimeter band. Total weight gain is expected to be between 17 and 24 pounds.

The 28-week prenatal visit is one of the most procedurally dense visits of the entire pregnancy. Two things happen for most patients, and one happens for some.

For everyone: kick counts. The APA's listing for the week-28 visit specifically includes "Instructions on how to calculate kick counts". The standard protocol is sometimes called "count to ten": pick a time of day when your baby is usually active (typically after a meal), lie on your left side, and count distinct movements. Ten movements should arrive within two hours; for most babies, ten arrive within thirty minutes. The point is not the number, the NHS guidance is that there is "no set number of movements" universally, the point is establishing a baseline so you can recognize a change.

For everyone with Rh-negative blood: the RhoGAM injection. About 15% of people have Rh-negative blood. If the baby is Rh-positive, the parent's immune system can develop antibodies that attack fetal red blood cells in this pregnancy or, more commonly, the next one. MedlinePlus explains that an injection of RhoGAM during the second/early third trimester blocks this response — and that, with the protocol followed, "Rh incompatibility is almost completely preventable." The injection is into the muscle, takes a minute, and is roughly as uncomfortable as a flu shot.

For anyone who hasn't yet done the glucose screen: this is the last conventional week for it.

Additional symptoms tend to arrive in week 28. Heartburn, which the NHS specifically flags this week. Leg cramps and constipation, which the APA mentions. Hemorrhoids, which roughly half of pregnant people develop in the third trimester. Insomnia, which approximately every pregnant person on earth develops in the third trimester. The recurring fix for almost all of it is hydration, fiber, side-sleeping, and elevating your feet when you can.

What your partner can do

Three things matter most for partners in the opening week of the third trimester. The first is to start tracking things alongside the pregnant person. Three concrete tasks.

Know the kick-count routine. The APA's recommendation to log fetal movements is one of the few prenatal monitoring tools that requires daily attention. Most people use a notes app or a printed chart on the fridge. As a partner, you do not need to count for them — you need to know what their pattern looks like, so when they say "the baby was active during dinner," you can confirm or notice the absence. The partner who can answer "was the morning busy or quiet?" is doing meaningful prenatal monitoring.

Finish the nursery hardware. Cribs, dressers, and changing tables that require assembly are dramatically harder to put together when you are sharing a room with a newborn. Week 28 is a reasonable target for having the big pieces in place — not because the baby is coming next week, but because the next eight weeks may include sciatica, swelling, and a fundamental inability to find a comfortable position. Build the crib while you can still kneel comfortably.

Deal with the financial paperwork. The list is unglamorous and small but heavy if it goes unhandled until week 38: updating health insurance plans for the open-enrollment window, adding the baby to the policy in the legally required time after birth, understanding parental leave at both jobs, knowing what FSA or HSA balances need to be spent. None of this is exciting. All of it is much easier handled at week 28 than at week 35.

The pregnant person is also, with high probability, dealing with sleep loss. The third-trimester insomnia is brutal and badly underrepresented in the cultural conversation about pregnancy. The single best thing a partner can do is take over the night-routine chores that have been creeping back to the pregnant person — locking the door, setting the coffee, walking the dog one last time. Buy them an extra forty minutes of horizontal time. They will not forget it.

Names we love this week

Week 28 has the texture of a beginning. The third trimester opens, the calendar gets short, and the names that have been on the long list start to feel like real candidates. Couples who arrive at week 28 still arguing about the same name are usually arguing about something else; why couples disagree about baby names is a useful frame for the conversation. The names that fit it are the ones that hold a starting point in their meaning.

• Nova means "new" in Latin. A name for a baby starting a new trimester, a new visible roundness, a new chapter of the calendar. It is also one of the fastest-rising girls' names in the US over the past decade.
• Hazel — English "the hazel tree" — clean for third-trimester start.
• Genesis means "origin, beginning" in Greek. A name that has been steadily climbing US girls' lists, and is increasingly used regardless of religious tradition.
• August means "great, magnificent" in Latin. It works for any gender and reads as both a month and a name, which means it carries a sense of time embedded in it.
• Maverick is American English for an unbranded calf — by extension, an independent thinker. The name has climbed into the top 50 over the past five years and shows no sign of stopping.
• Roman is straightforward in meaning and uncluttered in sound. A two-syllable boys' name with steady popularity and a quietly classical feel.
• Esme is French for "loved, esteemed." Quietly used in the UK for decades, only recently rising in the US. Two syllables, no waste.
• Lincoln means "town by the pool" in Old English, but the president is what most people hear. Used widely now as a first name and increasingly as a girls' name as well.

A small piece of advice for week 28: the kick-count log you start this week becomes the most consistent data you have on this pregnancy. Most people use it for two weeks and stop. Don't stop. Five minutes a day of attention to fetal movement is the single most accessible safety net of the third trimester, and the night you call your midwife about a quiet day is the night you will be glad you had the prior twelve days of data to compare against.

Sources

• American Pregnancy Association — Week 28 of Pregnancy
• NHS — 28 weeks pregnant
• Cleveland Clinic — Fetal Development: Stages of Growth
• MedlinePlus — Rh incompatibility
• NHS — Your baby's movements