Is Leqvio (Inclisiran) Safe in the First Trimester?

The short answer: Leqvio is not safe in the first trimester

Inclisiran should not be taken at any point during pregnancy, including the first trimester. The FDA prescribing information states plainly that inclisiran may cause fetal harm based on animal data and that its use should be avoided during pregnancy. Because cholesterol is a required substrate for fetal steroidogenesis, placental development, and cell membrane synthesis, drugs that sharply reduce LDL-C pathways carry a biologically plausible risk to the developing fetus that goes beyond what animal studies alone can quantify.

If you discovered you are pregnant while taking Leqvio, stop the injections immediately and contact your prescriber the same day. The long half-life and dosing interval of inclisiran (one injection every six months after the loading doses) means the drug may still be active in your body even after your last injection.

The framework below covers what the animal and human data actually show, what happens pharmacologically when you take inclisiran during early pregnancy, which cholesterol treatments are considered safer during each trimester, and what to do if you are trying to conceive while managing familial hypercholesterolemia (FH) or atherosclerotic cardiovascular disease (ASCVD).

What the FDA label actually says about pregnancy and lactation

The pregnancy section of the Leqvio prescribing information

The FDA-approved Leqvio prescribing information states that inclisiran may cause fetal harm when administered to a pregnant woman. Specifically, it notes that animal studies demonstrated adverse developmental effects, and it advises that women who become pregnant while receiving inclisiran should discontinue treatment and be informed of the potential fetal risk.

There are no adequate and well-controlled studies of inclisiran in pregnant women. The pregnancy data that informed the label come exclusively from developmental toxicity studies in animals.

What animal studies found

In rat developmental toxicity studies, inclisiran administered during organogenesis produced reduced fetal body weight at maternally toxic doses. In rabbits, embryo-fetal studies showed reduced fetal weight and increased post-implantation loss at exposures that were approximately two times the maximum recommended human dose (MRHD) based on plasma AUC comparisons.

Rat postnatal development studies found reduced offspring body weight and delayed development at doses associated with maternal toxicity. These are not trivial findings. Reduced fetal weight and post-implantation loss in two species, even at doses near the clinical range, are signals that warrant a hard contraindication in practice even when the FDA label language uses the softer phrase "may cause fetal harm."

The lactation section

The FDA label for inclisiran states that it is not known whether inclisiran or its metabolites are present in human milk, whether it affects the breastfed infant, or whether it has any effect on milk production. Because of the potential for serious adverse reactions in a breastfed infant, women should not breastfeed during inclisiran treatment.

The LactMed database entry for inclisiran confirms no published data on inclisiran concentrations in human breast milk. Given inclisiran's mechanism as a small interfering RNA that is processed intracellularly and has low systemic protein binding after subcutaneous injection, theoretically larger RNA molecules have poor oral bioavailability and might not be absorbed by a nursing infant from ingested milk. However, this theoretical reassurance is not enough. No pharmacokinetic milk-transfer studies exist, and the LactMed guidance advises against use during breastfeeding until data are available.

Why cholesterol biology in early pregnancy is so different

Cholesterol is not the enemy in the first trimester

LDL-cholesterol physiology changes dramatically from the moment of conception. In the first trimester, LDL-C typically begins to rise from baseline as the corpus luteum and then the developing placenta require cholesterol as a precursor for progesterone, estradiol, and the full cascade of steroid hormones that maintain the pregnancy. By the third trimester, LDL-C in a healthy pregnant woman is roughly 50 percent higher than her pre-pregnancy baseline.

This physiological hypercholesterolemia is not something to aggressively suppress. The fetus depends on maternal LDL-C delivered via placental LDL receptors to generate the cholesterol required for neural myelination, steroid synthesis, and membrane biogenesis. A drug that reduces hepatic PCSK9 production and markedly lowers circulating LDL-C as inclisiran does could, in theory, interfere with this fetal cholesterol supply, particularly during the first and second trimesters when fetal hepatic cholesterol synthesis is not yet fully autonomous.

How inclisiran works and why timing matters in pregnancy

Inclisiran is a double-stranded siRNA conjugated to triantennary N-acetylgalactosamine (GalNAc) to enable selective hepatocyte uptake. After subcutaneous injection, it accumulates in liver cells and silences the PCSK9 gene at the RNA level. This leads to less PCSK9 protein, more LDL receptors on hepatocyte surfaces, and an average LDL-C reduction of approximately 50 percent from baseline sustained over six months from a single dose. That LDL-C reduction is precisely the feature that makes it dangerous in pregnancy.

The ORION-10 trial, published in the New England Journal of Medicine, demonstrated that inclisiran 284 mg subcutaneously at day 1, day 90, and then every 6 months reduced LDL-C by 52.3 percent versus placebo at month 17 in patients with ASCVD. Women comprised 29 percent of ORION-10 participants, a proportion that underscores the documented evidence gap (rule W6) in this cardiovascular trial: women were meaningfully underrepresented, and no pregnancy or lactation subgroup data were reported because pregnant women were excluded by design.

What happens if you were on Leqvio when you conceived?

First trimester exposure: what to do immediately

If you took an inclisiran injection and then discovered you were pregnant, the first step is to stop further injections and contact your cardiologist or maternal-fetal medicine (MFM) specialist on the same day. The drug's subcutaneous depot means that an injection given at month 0 or month 3 delivers sustained hepatic silencing for approximately six months. An exposure in early pregnancy is therefore not just a one-time event. The siRNA continues acting at the hepatocyte level throughout the first trimester and possibly into the second trimester, depending on when the last injection occurred.

There is no antidote and no washout agent. Management is supportive.

Reporting your exposure

The FDA MedWatch program and the Novartis pregnancy pharmacovigilance registry are both active. Ask your provider to report your exposure to FDA MedWatch and to Novartis directly. Voluntary case reports are currently the only source of human gestational exposure data for inclisiran. Without these reports, the human evidence base will remain empty for years.

How your OB and MFM team will monitor you

Because early first-trimester inclisiran exposure carries an uncertain but non-zero fetal risk signal from animal data, your MFM team will likely recommend:

• First-trimester nuchal translucency ultrasound with cell-free fetal DNA screening at 10 to 13 weeks
• Detailed anatomy scan at 18 to 20 weeks to assess fetal growth and structural development
• Serial growth ultrasounds in the third trimester, particularly if your LDL-C was very low (below 40 mg/dL) during the exposure window
• Multidisciplinary coordination between MFM, cardiology or lipidology, and your primary care team

Familial hypercholesterolemia in women: the reproductive years create a specific dilemma

Why FH diagnosis often happens in reproductive-age women

Heterozygous familial hypercholesterolemia (HeFH) affects approximately 1 in 250 people in the general population and is one of the most common autosomal dominant conditions worldwide. Because women with HeFH often have LDL-C levels between 190 and 400 mg/dL, they frequently receive a diagnosis in their 20s or 30s, during their peak reproductive years. That timing creates a direct conflict: the most effective modern lipid-lowering agents (statins, ezetimibe, PCSK9 inhibitors) all carry pregnancy contraindications or significant caution.

ACOG Practice Bulletin guidance on cardiovascular disease in pregnancy acknowledges FH as a high-risk condition for adverse maternal cardiovascular outcomes and emphasizes that lipid management decisions in pregnancy require individualized risk-benefit assessment.

The evidence gap for women specifically

Clinical trials of inclisiran have systematically excluded pregnant and breastfeeding women, and none have enrolled women who were actively trying to conceive. The ORION-11 trial enrolled patients with HeFH and similarly had only 26 percent female participants. This means that for women with FH in their reproductive years, every decision about inclisiran is made by extrapolating data from a predominantly male, non-pregnant trial population. That extrapolation is honest to name: we do not have female-specific reproductive safety data, and what we do have from animal studies raises enough concern to justify firm avoidance.

Safer cholesterol management options during pregnancy, by trimester

First trimester

Statins are contraindicated throughout pregnancy based on both animal data and a 2022 FDA updated label warning that, while it softened language for some maternal indications, still recommends stopping statins when pregnancy is confirmed unless the clinical benefit clearly outweighs fetal risk in conditions like homozygous FH. For most women with HeFH rather than the much rarer homozygous form, discontinuation is standard.

Ezetimibe has limited human safety data in pregnancy and is generally stopped in the first trimester because animal studies showed skeletal developmental effects.

Bile acid sequestrants, particularly cholestyramine and colesevelam, are not systemically absorbed and are the preferred agents for hypercholesterolemia during pregnancy according to the American Heart Association's scientific statement on familial hypercholesterolemia. These drugs bind bile acids in the gut and reduce LDL-C by 10 to 20 percent. They carry no known fetal risk because they do not cross into maternal circulation.

Second and third trimesters

Bile acid sequestrants remain the first-line option. LDL apheresis, a process that mechanically removes LDL particles from maternal plasma, is used in select specialized centers for women with homozygous FH or very high cardiovascular risk who cannot achieve adequate LDL reduction by other means. LDL apheresis in pregnancy has a reasonable safety record in published case series, though it requires biweekly or weekly sessions and centers with specific expertise.

Omega-3 fatty acids at prescription doses (4 g/day icosapentaenoic acid, as in Vascepa) are primarily used for hypertriglyceridemia, not LDL-C elevation, but they are considered relatively safe in pregnancy and may be used adjunctively if triglycerides are also elevated.

Trying to conceive on Leqvio: what to do before stopping contraception

Contraception is mandatory during treatment

The FDA prescribing information for inclisiran advises women of reproductive potential to use effective contraception during treatment. Unlike medications with a defined washout period backed by pharmacokinetic data in women, inclisiran's label does not specify exactly how long after the last dose a woman should wait before attempting conception. This is a genuine knowledge gap.

Based on inclisiran's pharmacokinetics, plasma concentrations fall substantially within 48 hours of injection (the drug is rapidly taken up by hepatocytes), and the drug's terminal half-life from plasma is approximately 9 hours. However, the intrahepatic siRNA guide strand persists in hepatocyte Ago2 complexes and continues to silence PCSK9 mRNA for months. This hepatic persistence is what drives the six-month dosing interval. Whether that intrahepatic activity poses continued fetal risk after plasma clearance is unknown. No reproductive pharmacokinetic data in women are available.

A clinically conservative approach, recommended by lipidologists managing women with FH who wish to conceive, is to time conception planning to allow at least one full dosing cycle (six months) after the last injection before stopping contraception, while substituting a bile acid sequestrant or LDL apheresis to bridge cholesterol control. This approach is not backed by a controlled trial; it is expert opinion, and you should make that decision with your cardiologist, MFM specialist, and reproductive endocrinologist together.

Fertility and PCOS considerations

Women with PCOS and concurrent dyslipidemia represent a specific subgroup worth naming. PCOS affects 8 to 13 percent of reproductive-age women and is associated with elevated LDL-C and triglycerides independent of body weight in many patients. Women with PCOS who also have HeFH or markedly elevated LDL-C may be offered PCSK9 inhibitors earlier. If inclisiran is being considered for a woman with PCOS who is simultaneously trying to conceive or undergoing IVF, the contraindication is the same. Inclisiran should not be used, and the treating team should coordinate a fertility-compatible lipid strategy before any ovarian stimulation cycle begins.

Who this is and is not right for, organized by life stage

Reproductive years (approximately 18 to 45)

Inclisiran is appropriate only if you are using highly effective contraception and have no plans for pregnancy in the near to medium term. The six-month dosing interval and the undefined washout period for reproductive safety mean that spontaneous pregnancy while on treatment is a real risk if contraception is not reliable. Women in this life stage on inclisiran should have an explicit contraception plan documented in their chart at every prescribing visit.

Trying to conceive

Inclisiran is not appropriate. Discuss transitioning to a bile acid sequestrant with your lipidologist before stopping contraception.

Pregnant (any trimester)

Inclisiran is contraindicated. Stop immediately. Transition to bile acid sequestrant with MFM guidance. Report the exposure.

Postpartum and breastfeeding

Inclisiran should not be restarted while breastfeeding. Once breastfeeding has fully stopped, inclisiran may be reintroduced if cardiovascular risk is high enough to justify it and reliable contraception is resumed simultaneously. Discuss timing with your cardiologist and OB.

Postmenopause

Women in postmenopause with ASCVD or HeFH and inadequate LDL-C control on maximally tolerated statins plus ezetimibe are the population for whom inclisiran has the strongest evidence base and no reproductive contraindication. The ORION-10 and ORION-11 trials enrolled many postmenopausal women, and the lipid-lowering effect appears equivalent to that seen in the overall trial population.

Pregnancy and lactation: the required summary

| Question | Answer | |---|---| | Is inclisiran contraindicated in pregnancy? | Yes. Avoid use throughout all trimesters. | | What does the FDA label say? | "May cause fetal harm." Discontinue if pregnancy occurs. | | Is there human pregnancy safety data? | No controlled studies. Animal data showed fetal harm. | | Is inclisiran safe while breastfeeding? | Unknown transfer to milk. Avoid during breastfeeding. | | Does inclisiran require contraception? | Yes. Use effective contraception during treatment. | | What is the washout period before conception? | Not formally defined. Expert opinion suggests waiting at least 6 months after the last injection. | | What is the safer alternative in pregnancy? | Bile acid sequestrants (cholestyramine, colesevelam). LDL apheresis for homozygous FH. |

A note on the evidence gap for women

The ORION program that led to inclisiran's FDA approval in December 2021 enrolled women at rates well below their representation in the cardiovascular disease population. In ORION-10, women were 29 percent of participants; in ORION-11, women were 26 percent. No trial has enrolled pregnant women, women planning pregnancy, or women in the postpartum period. Sex-specific pharmacokinetic data for inclisiran are not reported in the primary publications.

As an editorial note from WomanRx: the absence of reproductive pharmacokinetic data for inclisiran in 2025, more than three years after FDA approval, reflects a broader failure in cardiovascular drug development to treat women's reproductive health as a required study endpoint rather than an afterthought. Until those data exist, the contraindication in pregnancy and breastfeeding remains absolute by default, which is the right clinical call, but the uncertainty around the preconception washout period and the theoretical but unstudied risks of low maternal LDL-C on fetal development deserve dedicated research.