You Had a Premature Baby. Here Is What to Do in Your Next Pregnancy.

Know Your Numbers, Trust Your Body

Her first baby came at 28 weeks. She remembers the night it started. Cramping she thought was indigestion. A backache she blamed on the way she’d been sleeping. A trickle of fluid she almost ignored. Within six hours, she was in a delivery room watching doctors work on a baby the size of a loaf of bread.

Her son spent 67 days in the NICU. He came home on oxygen. He’s four now and doing well.

She is pregnant again. And she is terrified.

The first question she asked at her initial prenatal visit was the question every woman in her situation asks: “Is this going to happen again?”

The honest answer is: it might. But there are things we can do to significantly lower that risk. Real, evidence-based interventions. Not bed rest. Not “taking it easy.” Not wishful thinking. Specific medical steps that have been shown in clinical trials to reduce the chance of another premature delivery.

The problem is that many women don’t know about these steps. And too many providers don’t implement them consistently.

How High Is Your Risk, Really?

Let’s start with numbers, because you deserve to know them.

A prior spontaneous preterm birth is the single strongest risk factor for having another one. If you delivered one baby preterm, your risk of recurrence is roughly 15% to 30%, depending on how early your first delivery was and other factors [1,2]. Compare that to the baseline risk of about 5% for a woman with no history of preterm birth.

The earlier the prior delivery, the higher the risk. A population-based study of over 19,000 third births found that women with two prior preterm deliveries had a 42% recurrence rate. For women with two prior very preterm deliveries (before 32 weeks), the recurrence rate was 57% [3]. A large Norwegian registry study of over 213,000 women confirmed that the gestational age of the first birth is a powerful predictor: women who delivered extremely preterm had the highest odds of a subsequent preterm birth, regardless of other maternal or obstetric factors [4].

Data from the Brazilian CIDACS cohort of over 1.7 million women showed that among those with a prior preterm birth, 18% delivered preterm again, compared to 7% of women whose first pregnancy was at term [5].

These numbers are sobering. But notice what they also tell you: even among the highest-risk women, the majority still deliver at term. A 30% recurrence risk means a 70% chance of making it to full term. That’s important context. The goal of everything that follows is to push that number even higher in your favor.

The risk is also modified by what happened since your preterm delivery. If you had a subsequent full-term pregnancy, your risk drops substantially. A study published in the American Journal of Perinatology found that a term birth as the most recent delivery lowered the recurrence rate to around 19% compared to 38% when the most recent delivery was preterm [6].

Black women face a disproportionate burden. The preterm birth rate for Black women is 14.7% compared to 9.5% for White women [7]. This disparity persists even among college-educated women with private insurance, where Black women still have preterm birth rates nearly double those of White women [8]. This is not biology. This is the measurable health consequence of structural racism, chronic stress, and inequities in healthcare access and quality.

The Drug That Was Supposed to Prevent This

For over a decade, obstetricians had a go-to treatment for preventing recurrent preterm birth: 17-alpha hydroxyprogesterone caproate, a weekly intramuscular injection sold as Makena. It was approved by the FDA in 2011 through the accelerated approval pathway based on a single trial by Meis and colleagues, published in the New England Journal of Medicine in 2003, which showed a significant reduction in recurrent preterm birth [9].

There was a catch. Accelerated approval requires a confirmatory trial. That trial, called PROLONG, enrolled 1,708 women across multiple countries and was published in 2019. It found no benefit. Makena did not reduce recurrent preterm birth. It did not improve any neonatal outcome [10].

On April 6, 2023, the FDA withdrew approval of Makena and all its generics, effective immediately. The advisory committee vote was overwhelming: 14 to 1 against keeping it on the market [11]. The FDA Commissioner stated plainly that Makena had not been shown to be effective and that no level of risk is justified for a drug without demonstrated benefit [12].

This was a watershed moment. For over a decade, hundreds of thousands of pregnant women received weekly injections of a drug that, as it turned out, didn’t work. The healthcare system spent over $700 million on Makena through Medicare and Medicaid alone between 2018 and 2021 [13]. All for an intervention that a larger, better-designed trial could not confirm.

The Society for Maternal-Fetal Medicine (SMFM) responded clearly: “We agree with the FDA determination and discourage continued prescribing of 17-OHPC, including through compounding pharmacies” [14].

So if the drug that was supposed to prevent recurrent preterm birth doesn’t work, what does?

What Actually Works: Cervical Length Screening

Here is what the evidence supports: the single most important thing you can do if you’ve had a prior spontaneous preterm birth is get your cervix measured. Regularly. By transvaginal ultrasound. Starting at 16 weeks.

The cervix is the gateway between the uterus and the vagina. During pregnancy, it’s supposed to stay long and closed. When it shortens prematurely, silently, without contractions you can feel, it can lead to preterm labor and delivery. This process, called cervical insufficiency or premature cervical ripening, is one of the primary pathways to spontaneous preterm birth.

A transvaginal ultrasound can measure cervical length with remarkable precision and reproducibility, with an interobserver variation rate of only 5% to 10% [15]. It is safe. It is painless. It takes minutes.

Both ACOG and SMFM recommend serial transvaginal cervical length screening for women with a singleton pregnancy and a history of prior spontaneous preterm birth. This is a Grade 1A recommendation, the highest level of evidence-based certainty [15,16]. Screening is performed every one to two weeks from 16 to 24 weeks of gestation.

A cervical length below 25 mm at this gestational age is considered short. At 18 to 24 weeks, the 10th percentile of cervical length corresponds to about 25 mm. The shorter the cervix, the higher the risk. And the shorter the cervix, the greater the benefit of intervention.

Here is the critical point for patients: if you have had a prior spontaneous preterm birth and you are not being offered cervical length screening in your current pregnancy, ask for it. This is not optional monitoring. This is a Class 1A recommendation from both major professional organizations in obstetrics [15,16]. If your provider is not doing this, bring it up.

When the Cervix Is Short: Vaginal Progesterone

If serial screening reveals that your cervix is shortening, specifically to 25 mm or less before 24 weeks, there is an intervention with strong evidence of benefit: vaginal progesterone.

A 2022 BMJ network meta-analysis, the most comprehensive comparison of preterm birth prevention strategies to date, examined 61 trials involving over 17,000 pregnant women. The conclusion was unambiguous: vaginal progesterone was the only intervention that showed clear, high-certainty evidence of reducing both preterm birth before 34 weeks (odds ratio 0.50) and perinatal death (odds ratio 0.66) compared to placebo [17]. No other intervention matched it for the combination of proven efficacy and safety.

The evidence shows vaginal progesterone reduces preterm birth before 33 weeks with a number needed to treat (NNT) of 14. That means for every 14 women treated, one preterm birth is prevented. The NNT to prevent one case of neonatal respiratory distress syndrome is 22 [18].

The individual patient data meta-analysis by Romero and colleagues confirmed that for women with a singleton pregnancy, a history of spontaneous preterm birth, and a short cervix (25 mm or less), vaginal progesterone significantly reduced preterm birth before 35 weeks (RR 0.68) and before 32 weeks (RR 0.60), as well as composite perinatal morbidity and mortality (RR 0.43), neonatal sepsis (RR 0.38), and NICU admission (RR 0.46) [19].

The typical regimen is 200 mg of micronized progesterone (Prometrium) inserted vaginally each night, started when the short cervix is identified (ideally by 24 weeks) and continued until 36 weeks of gestation.

But here is what the evidence also tells us, and this is where the nuance matters: vaginal progesterone has NOT been shown to prevent recurrent preterm birth in the absence of a short cervix. A meta-analysis and a large study both found that vaginal progesterone does not reduce preterm birth in women whose cervical length is greater than 25 mm, even if they have a history of preterm birth [20,21]. ACOG’s updated 2023 Practice Advisory states this explicitly [22].

This is why cervical length screening is not just recommended but essential. Progesterone works when the cervix is short. Without knowing your cervical length, neither you nor your doctor can make an informed decision about whether progesterone will help you.

When the Cervix Is Very Short: Cervical Cerclage

Cervical cerclage is a surgical procedure in which a suture is placed around the cervix to reinforce it and help keep it closed. It has been used for over 60 years. The evidence for its use is nuanced.

For women with a prior spontaneous preterm birth before 34 weeks AND a cervical length less than 25 mm on transvaginal ultrasound, the landmark MFMU Network trial by Owen and colleagues found that cerclage reduced previable birth (before 24 weeks) and perinatal mortality [23]. However, it did not significantly reduce the overall rate of birth before 35 weeks, unless the cervical length was very short, below 15 mm, where the reduction was significant [23].

A Cochrane systematic review of cerclage in singleton pregnancies found that cerclage reduced the risk of preterm birth before 37, 34, and 28 weeks when performed in women with specific indications [24].

The data suggest the following approach, which aligns with current guidelines from ACOG, SMFM, RCOG, NICE, and FIGO:

History-indicated cerclage (placed at 12 to 14 weeks without waiting for cervical shortening) may be appropriate for women with a classic history of cervical insufficiency: painless second-trimester dilation, prior second-trimester loss, or prior cerclage in a previous pregnancy [25].

Ultrasound-indicated cerclage (placed when serial monitoring reveals a cervical length below 25 mm) is recommended for women with a prior spontaneous preterm birth before 34 weeks whose cervix shortens during surveillance [15,23].

A 2023 systematic review and meta-analysis found that combining cervical cerclage with vaginal progesterone may be more effective than either intervention alone, with a roughly threefold reduction in preterm birth before 32 weeks and a fourfold reduction in neonatal mortality compared to cerclage alone [26]. This combination approach is an area of active investigation and discussion.

What the guidelines do NOT support: cerclage placement solely based on a short cervix in the absence of a prior preterm birth or pregnancy loss. For those women, vaginal progesterone is the recommended first-line treatment [16,25].

What Does NOT Work (Despite What You May Hear)

Let me be direct about interventions that are still commonly prescribed or advised but are not supported by evidence for preventing recurrent preterm birth.

Bed rest. There is no evidence that bed rest prevents preterm birth. None. Multiple studies have failed to demonstrate benefit, and prolonged bed rest carries real risks: blood clots, muscle wasting, bone loss, depression, and financial hardship. Neither ACOG nor SMFM recommends bed rest for preterm birth prevention [17].

Activity restriction. Similar to bed rest, there is no evidence that reducing physical activity prevents preterm birth.

Intramuscular progesterone (17-OHPC/Makena). As detailed above, the FDA withdrew this drug in 2023 for lack of efficacy. SMFM discourages its use, including from compounding pharmacies [14].

Prophylactic tocolytics. Medications used to stop contractions have not been shown to prevent preterm birth when given prophylactically.

If your provider recommends any of these, ask them to explain the evidence supporting their recommendation. You have every right to do so.

Your Action Plan: What to Ask For

If you have had a prior spontaneous preterm birth and you are pregnant again, or planning to become pregnant, here is what the evidence says you should do.

Before pregnancy. See a maternal-fetal medicine specialist for a preconception consultation. Discuss the circumstances of your prior preterm birth. Was it spontaneous (preterm labor or preterm rupture of membranes) or medically indicated (for preeclampsia, growth restriction, or another complication)? The distinction matters because the prevention strategies are different. Optimize modifiable risk factors: quit smoking, treat infections, achieve a healthy interpregnancy interval of at least 18 months.

At your first prenatal visit. Make sure your provider knows the exact details of your prior preterm birth, including the gestational age, whether it was spontaneous, and whether you had a cerclage. Discuss whether you need a referral to maternal-fetal medicine for co-management or consultation.

Starting at 16 weeks. Begin serial transvaginal cervical length screening every one to two weeks, continuing until 24 weeks [15,16]. This is a Grade 1A recommendation. If your provider does not offer this, ask for it or request a referral to someone who does.

If your cervix shortens to 25 mm or less before 24 weeks. Discuss vaginal progesterone (200 mg nightly) with your provider. Discuss whether cervical cerclage is appropriate given your specific history. For women with a very short cervix (below 15 mm), cerclage may offer additional benefit [23].

If your cervix remains normal. Continue regular prenatal care. Know the signs of preterm labor: regular contractions (more than four per hour), low pelvic pressure, low back pain, change in vaginal discharge, any fluid leaking. Trust your instincts. If something feels different, call.

Throughout pregnancy. Know that you are being monitored more closely than a woman without this history. Your anxiety is valid. Your fear is reasonable. And the monitoring exists because it works.

The Bigger Problem We Need to Talk About

Here is what bothers me as an obstetrician.

For twenty years, we had a drug, Makena, that we gave to hundreds of thousands of women. It turned out not to work. The confirmatory trial was finished in 2018, but the FDA didn’t withdraw the drug until 2023. During that interval, the healthcare system spent hundreds of millions of dollars on an ineffective intervention while the actual evidence-based approach, cervical length screening with vaginal progesterone for short cervix, remained underutilized.

Women with prior preterm births account for only about 10% of all deliveries before 34 weeks [15]. That means the vast majority of preterm births occur in women with no history to trigger enhanced screening. Universal cervical length screening at the time of the anatomy ultrasound (18 to 23 weeks) could identify many of these women and offer them vaginal progesterone. A 2024 meta-analysis found that universal screening was associated with a significant reduction in spontaneous preterm birth before 37 weeks compared to no screening [27].

Yet ACOG and SMFM still do not recommend universal cervical length screening. They say practitioners who decide to implement it should follow strict guidelines, but they stop short of recommending it for all women [15,16]. Meanwhile, preterm birth rates in the United States continue to rise. They increased by over 10% between 2011 and 2022 [28].

The prevention tools exist. The challenge is implementation and the courage to use them broadly.

What This Comes Down To

If you’ve had a premature baby, your next pregnancy will be different. It will carry more anxiety, more monitoring, and more medical visits. That is the reality.

But it will also carry more knowledge, more tools, and more evidence-based options than existed even a few years ago.

Get your cervix measured. Serial transvaginal ultrasound from 16 to 24 weeks is the single most important surveillance tool. It’s a Grade 1A recommendation. Don’t leave it to chance.

If your cervix is short, use vaginal progesterone. The evidence is strong. It reduces preterm birth. It reduces perinatal death. It reduces NICU admissions.

If your history warrants it, discuss cerclage. For selected women with very early prior deliveries or very short cervices, cerclage can be lifesaving.

Don’t accept bed rest, activity restriction, or compounded 17-OHPC as substitutes for evidence-based care. You deserve interventions that have been shown to work.

The woman from our opening story? In her second pregnancy, she was screened every two weeks starting at 16 weeks. At 20 weeks, her cervix measured 22 mm. She started vaginal progesterone that night. She was offered cerclage and, after a shared decision-making conversation with her MFM specialist, elected to proceed. She delivered at 37 weeks and 4 days. A healthy girl. No NICU stay. No oxygen. She went home in two days.

It was not the same pregnancy. But it was a good outcome. An evidence-based outcome.

You can have one too.

If this was helpful, share it with someone who needs it. Every woman with a prior preterm birth deserves to know her options.

Subscribe to ObGyn Intelligence for more evidence-based guidance on pregnancy, reproductive health, and the gap between what we know and what we do.

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References

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