Getting Close to the Home Stretch
Week 25 marks the point where the last quarter of pregnancy starts to come into view. The third trimester begins at week 28, just three weeks away. Your baby is filling out, moving regularly, and making their presence known in increasingly physical ways.
This is also the week to start thinking about two upcoming clinical milestones: the glucose screening test, which typically happens around week 26, and your Rh factor status, which if negative, will require a prophylactic injection at about week 28. Neither of these is a reason for alarm. Both are routine parts of second trimester care that protect you and your baby.
Your Baby This Week
Your fetus is now roughly the size of a zucchini, measuring about 13.6 inches (34.6 cm) from head to heel and weighing approximately 1.5 pounds (680 grams) [2]. Growth this week is concentrated in the lungs and musculature.
- The grasp reflex is strong. Your baby can now close a hand firmly and, if they grab the umbilical cord, may hold on. This reflex will be present at birth and is how newborns grip your finger in those first moments [3].
- Lung capillaries are forming. The dense network of blood vessels that will eventually exchange oxygen across the alveolar walls is developing in the lung tissue. This vascular infrastructure is essential for the lungs to function after birth [5].
- Nostrils are opening. The nostrils, which were plugged during earlier development, are now opening. The fetus begins practicing breathing movements, drawing small amounts of amniotic fluid in and out of the lungs [2].
- Fat accumulation is accelerating. The lean, translucent appearance of a few weeks ago is giving way to a more filled-out look as white adipose tissue deposits under the skin [3].
Glucose Screening Prep: What to Expect Next Week
The one-hour glucose challenge test (GCT) is typically scheduled around weeks 24 to 28 and is one of the most-discussed tests in the second trimester. Here is what to know before you walk in [1]:
What it screens for. The test checks for gestational diabetes mellitus (GDM), a form of glucose intolerance that develops during pregnancy. GDM affects roughly 6 to 9 percent of pregnancies in the United States [1].
How the test works. You will be given a sweet, glucose-containing drink (usually 50 grams of glucose) to consume within five minutes. One hour later, your blood is drawn. The threshold for a "positive" (abnormal) result is typically around 130 to 140 mg/dL, depending on the laboratory your provider uses [1].
Do NOT fast before this test. The one-hour screen is designed to be performed in a non-fasting state. Eating a balanced meal or snack beforehand is fine, and some providers recommend it.
If your result is above the threshold. An elevated one-hour result does not diagnose gestational diabetes. It triggers a three-hour glucose tolerance test (GTT), which is the definitive diagnostic test. About two-thirds of women who fail the one-hour screen pass the three-hour test [1].
Risk factors for GDM include BMI above 25, family history of type 2 diabetes, previous GDM, and polycystic ovary syndrome (PCOS). Women with multiple risk factors may be screened earlier than week 24 to 28 [1].
Rh Factor: A Note If Your Blood Type Is Negative
If your blood type is Rh-negative (A-, B-, O-, or AB-), you will receive an injection of Rh immunoglobulin (RhIg, brand name RhoGAM) at approximately week 28 [4]. Here is why this matters:
If you are Rh-negative and your baby is Rh-positive (which is possible if the father is Rh-positive), your immune system may develop antibodies against your baby's blood cells if small amounts cross the placenta. This process, called Rh sensitization, is generally not a problem in a first pregnancy, but can cause serious complications called hemolytic disease of the newborn (HDN) in future pregnancies [4].
RhIg prevents sensitization from occurring. It is a routine, safe, and highly effective preventive measure. Your blood type was checked at your initial prenatal labs. If you're Rh-negative, your MomDoc provider will discuss RhIg timing at your upcoming visits [4].
Your Body at Twenty-Five Weeks
- Hemorrhoids. Increased blood volume, constipation, and pelvic pressure can cause the veins in the rectal area to swell and become painful or itchy. Staying hydrated, maintaining fiber intake, and avoiding prolonged sitting on the toilet can help. Over-the-counter topical treatments are generally safe, but confirm with your provider first.
- Carpal tunnel symptoms. Fluid retention during pregnancy can compress the median nerve at the wrist, causing tingling, numbness, or burning in the hands and fingers, particularly at night. Wrist splints worn while sleeping are a common and safe first-line approach.
- Round ligament discomfort may return. As the uterus rises further, the round ligaments supporting it continue to stretch. Sharp, brief pains on the sides of the lower abdomen are normal but should be distinguished from preterm contractions.
The Uncomfortable Truths
"I'm too embarrassed to tell anyone about the hemorrhoids." Hemorrhoids affect roughly half of pregnant women by the third trimester. They are caused by increased blood volume and the pressure of a growing uterus on pelvic veins. They are not a hygiene issue or a lifestyle failure. Your provider has heard about this thousands of times and can recommend safe treatments. The embarrassment you feel is the only part of this that is unnecessary.
"What if I fail the glucose test?" The glucose tolerance test is a screening tool, not a judgment. About 2-10% of pregnant women are diagnosed with gestational diabetes, and the diagnosis says nothing about your habits or choices. It reflects how your placenta is affecting insulin resistance. If you are diagnosed, your MomDoc team will build a management plan with you. Most women manage gestational diabetes through dietary adjustments alone, and it resolves after delivery.
What MomDoc Wants You to Know
Your glucose screening next week is a routine, brief appointment. Bring a book or something to occupy the one-hour wait. If you have specific concerns about GDM, your risk factors, or what a diagnosis would mean for the rest of your pregnancy, write those questions down and bring them to your next visit.
You are almost at the third trimester. The baby gripping the umbilical cord, practicing breaths in the fluid, learning the sound of your kitchen and your playlists, is three weeks away from a milestone that changes how everyone, including medicine, describes this pregnancy.