Okay, let's tackle this question about the most common cause of repeated second-trimester fetal loss. The user provided the question but didn't list the options. Hmm, but maybe they just forgot to include them. The correct answer is supposed to be the most common cause.

First, I need to recall the main reasons for second-trimester losses. The first thing that comes to mind is cervical insufficiency, also known as an incompetent cervix. That's when the cervix opens too early without contractions, leading to preterm delivery or miscarriage. It's a common cause, especially in recurrent cases during the second trimester. Other causes include placental issues like placenta previa or abruption, maternal conditions such as diabetes or hypertension, infections, and maybe chromosomal abnormalities. But chromosomal issues are more common in the first trimester, right?

Wait, the question specifies "repeated" losses. So recurrent. Cervical insufficiency is a leading cause of recurrent second-trimester losses. Placental problems might contribute too, but are they more likely to be one-time events? Also, maternal thrombophilias or autoimmune conditions like antiphospholipid syndrome can be involved. But I think cervical insufficiency is the top answer here.

Now, the options. Let's say the options are A: Cervical insufficiency, B: Chromosomal abnormalities, C: Placenta previa, D: Maternal diabetes. Then the correct answer would be A. But I need to make sure. Chromosomal abnormalities are more first trimester. Placenta previa is a placental issue that can cause bleeding but might not be the most common cause of repeated losses. Cervical insufficiency is a structural issue that can recur if not managed, like with a cerclage.

So in the explanation, the core concept is that cervical insufficiency is the leading cause of recurrent second-trimester fetal loss. The correct answer is right because it's a structural problem leading to premature cervical dilation. The other options are incorrect because chromosomal abnormalities are first trimester, placental issues are less common in recurrent cases, and maternal diabetes is a contributing factor but not the most common. The clinical pearl would be to remember that cervical insufficiency is a key cause and that cerclage is a treatment.

**Core Concept**
Recurrent second-trimester fetal loss (14–28 weeks) is most commonly caused by **cervical insufficiency**, a structural defect where the cervix dilates prematurely without contractions. This differs from first-trimester losses, which are predominantly due to chromosomal abnormalities.

**Why the Correct Answer is Right**
**Cervical insufficiency** (incompetent cervix) leads to painless cervical dilation and membrane rupture, often between 16–24 weeks. It is associated with a history of prior second-trimester losses, cervical trauma (e.g., from dilation and curettage), or congenital uterine anomalies. Diagnosis is confirmed via transvaginal ultrasound showing a short cervix (<25 mm) or funneling. Management includes cervical cerclage (surgical stitch) placement in early pregnancy. **Why Each Wrong Option is Incorrect** **Option A:** Chromosomal abnormalities are the leading cause of *first-trimester*

✓ Correct Answer: C. Abnormality of cervix and uterus