Weight Loss Medications and Pregnancy: What to Know Before Conceiving

If you’re a woman of reproductive age using weight loss medications, you may be wondering how these drugs affect fertility and pregnancy. It’s an important question: certain medications like semaglutide (Ozempic/Wegovy) can dramatically aid weight loss – and even unexpectedly boost fertility – yet they are not considered safe to use while trying to conceive or during pregnancy. In this post, we’ll walk through what you need to know about common weight loss meds (like semaglutide, metformin, and phentermine) when planning for pregnancy, and how to prepare for a healthy pregnancy after using them. We’ll keep it friendly and factual – so grab a cup of (decaf) tea, and let’s chat about this important topic.

How Weight Loss Medications Can Affect Fertility

Excess weight itself can interfere with fertility, so it’s not surprising that effective weight loss treatments might improve your chances of conceiving. In fact, many women have reported surprise “Ozempic® babies” – unexpected pregnancies that occurred after significant weight loss on GLP-1 medications like semaglutide. By helping patients lose an average of 15–20% of body weight, these GLP-1 drugs can lead to restored ovulation, more regular menstrual cycles, and balanced hormones in women with obesity. For example, in women with polycystic ovary syndrome (PCOS) – a common cause of infertility – losing weight often restores ovulation and regular periods, improving fertility. GLP-1 agonists (such as semaglutide or the similar drug tirzepatide) have been shown to normalize menstrual cycles and improve fertility in PCOS patients, so much so that they’ve been recommended in treatment guidelines for overweight women with PCOS.

That’s the “good” side: weight loss medications can indirectly boost fertility by helping you reach a healthier weight. However, there’s a big catch – these medications haven’t been studied or approved as fertility treatments, and we have very little data on their direct effects on reproduction. Drug trials for weight loss generally excluded women who were trying to get pregnant (for ethical and safety reasons). This means when it comes to using medications like Ozempic or phentermine around the time of conception, we’re cautious. It’s one thing to use these tools to lose weight before pregnancy; it’s another to stay on them once you’re actively trying to conceive. Next, we’ll break down the safety of specific weight loss drugs when you’re TTC (trying to conceive) or pregnant.

Common Weight Loss Medications and Pregnancy Safety

Semaglutide (Ozempic®/Wegovy® and other GLP-1s) and Pregnancy

GLP-1 receptor agonists – such as semaglutide (brand names Ozempic® for diabetes, Wegovy® for weight loss) and tirzepatide (Mounjaro®/Zepbound®) – are very effective for weight loss. But if you’re planning a pregnancy, these medications should be paused well in advance. The FDA and manufacturers recommend stopping GLP-1 drugs at least two months before trying to conceive. Why such a long lead time? These medications last a long time in your system – semaglutide can take up to about 6 weeks to clear from the body, so a two-month buffer ensures it’s fully gone. It’s also because we don’t know the full risks to a developing baby, and early pregnancy is when an embryo is most vulnerable.

Animal studies of semaglutide hinted at some potential issues (such as smaller offspring or pregnancy losses), though it’s unclear if that was due to the drug itself or the mother’s weight loss during pregnancy. In humans, the initial data is slightly reassuring – a study of 168 women who accidentally used GLP-1 drugs in early pregnancy (51 of them on semaglutide) did not find an increase in birth defects. That’s good news, but it’s a limited data set. Out of caution, experts say to err on the side of safety and discontinue these medications before pregnancy.

In practical terms: if you’re on a semaglutide-based weight loss program, plan to stop it at least 8 weeks before you start trying. And if you happen to get pregnant unexpectedly while on a GLP-1 medication, contact your provider and stop the medication right away. (Don’t panic – remember, no human birth defects were seen in that small study, but you’ll want to switch gears to a pregnancy-safe approach as soon as you know.) Your healthcare team will help you transition off the med and manage any issues like a return of appetite or blood sugar changes. Often, doctors will emphasize intensifying lifestyle measures (and possibly substitute other meds like metformin – more on that shortly) to keep you healthy after stopping a GLP-1. The bottom line is that Ozempic and similar drugs are not recommended when actively trying for a baby or during pregnancy. They’re fantastic tools to get to a healthy weight before pregnancy, but they should be out of your system once a baby is in the picture.

If you’re curious about how semaglutide compares to other options, check out our post on Semaglutide vs. Phentermine for weight loss.

Phentermine (Adipex-P®) and Other Stimulant Medications

Phentermine is an older weight loss drug (an appetite suppressant stimulant). It’s NOT safe to use during pregnancy, and in fact is classified by the FDA as pregnancy Category X (contraindicated in pregnancy). Doctors strongly advise women on phentermine to use contraception and discontinue the drug well before conceiving. The reason is twofold: intentional weight loss during pregnancy is unsafe for the baby, and we also have some evidence suggesting phentermine could directly cause fetal harm. For example, one review found hints of higher risk for issues like cleft palate, heart valve malformations, or even a rare fetal stroke when weight-loss drugs (phentermine being the most common) were used in early pregnancy. While definitive proof is hard to get (we can’t exactly do ethical experiments on this), the advice is crystal clear: do not take phentermine if you are pregnant or trying to become pregnant. If someone becomes pregnant while on it, they should stop immediately and call their doctor.

Phentermine also leaves the body faster than drugs like semaglutide (within days to a week or so in most people). Even so, it’s smart to stop phentermine well ahead of a planned pregnancy – not just to clear the drug, but to give your body time to stabilize (phentermine can have withdrawal effects like increased appetite once stopped). Many clinicians suggest coming off phentermine at least a few weeks (if not a couple of months) before trying to conceive. And as always, don’t use any other over-the-counter diet pills or herbal “fat burners” while pregnant either – those can be risky too. (For instance, the FDA has specifically warned against certain supplement ingredients like vinpocetine in pregnancy due to miscarriage and developmental risks.)

Metformin and Weight Management Before/During Pregnancy

Metformin is a bit of a special case. It’s actually a diabetes medication, not a primary weight-loss drug – but it’s sometimes used off-label for weight management, and it’s commonly used in women with PCOS to improve fertility. Unlike the other meds we’ve discussed, metformin is generally considered safe to continue in pregnancy (when medically indicated). In fact, OB/GYNs often keep women with PCOS or diabetes on metformin during pregnancy to help reduce the risk of miscarriage and gestational diabetes. Metformin doesn’t cause significant weight loss for most people (maybe a modest few pounds), but it improves insulin sensitivity and can indirectly help with weight stability. Importantly, metformin is not associated with birth defects and has a long track record of use in early pregnancy for metabolic support.

So, if you were prescribed metformin as part of your pre-pregnancy health plan – for example, to address insulin resistance or PCOS – your provider might actually continue it through conception and into pregnancy. Always follow your doctor’s guidance, but know that metformin is one weight-related medication that is often deemed safe in pregnancy (again, when there’s a medical reason for it). It can be a useful tool to bridge the gap after stopping drugs like semaglutide, to prevent rapid weight regain and maintain blood sugar control while you’re trying to conceive. In our practice, we’ve seen some women transition from a GLP-1 to metformin when planning pregnancy – this helps soften the landing, so to speak, and keep their momentum with healthy habits.

Read our detailed comparison of these medications in Metformin vs. Semaglutide for Weight Loss on our blog. 

Why Most Weight Loss Meds Should Be Stopped Before Pregnancy

To recap the key point: virtually all weight loss medications on the market are contraindicated during pregnancy. The fundamental reason is that deliberate weight loss and appetite suppression in pregnancy can harm a growing baby. During pregnancy, the goal is not weight loss – even for individuals with obesity, we aim for healthy weight gain (albeit a limited, appropriate gain). Restricting calories too much or taking a drug that curbs nutrition could lead to poor fetal growth or other complications. In fact, studies show that even in overweight women, actively losing weight while pregnant is associated with higher risk of having a small-for-gestational-age baby and other problems, which is why guidelines advise against weight-loss diets or meds in pregnancy.

Additionally, these medications themselves may have direct effects on a fetus that we either suspect (from animal data or case reports) or simply haven’t fully studied. With GLP-1 agonists (Ozempic, etc.), the concern (besides unknowns) is that if a woman stays on them and rapidly loses a lot of weight during pregnancy, it could increase risks of miscarriage, preterm delivery, preeclampsia, or other complications. With stimulant drugs like phentermine, there are concerns about blood flow and potential birth defects, as we discussed. Even newer pills for weight loss (like those combining naltrexone/bupropion or others) are not approved for use in pregnancy – all of them carry warnings to avoid if pregnant or trying.

The safest course is to discontinue weight-loss medications before conceiving (with enough lead time as recommended for each drug). If you find out you’re pregnant while on one, stop it immediately and inform your healthcare provider. Don’t be afraid that stopping the medication will doom your progress – yes, you might feel hungrier when you come off a med like semaglutide, but your doctors can help you adjust your nutrition plan to compensate. Your long-term health and the baby’s health are the priority now.

Preparing for Pregnancy After Using Weight Loss Meds

Okay, so you’ve been on a weight loss journey (maybe you lost a substantial amount of weight with help from a medication) and now you’re ready to grow your family. How can you safely transition into pregnancy? Here are some tips:

• Plan the Timing of Stopping: Work with your provider to figure out when to stop your medication. As noted, for GLP-1 agonists, stop ~2 months before TTC. For others like phentermine, stopping at least several weeks ahead is wise. This buffer allows your body to reach a new steady state without the drug. It also means by the time you could conceive, the medication is long gone.
  
• Manage Weight Changes After Stopping: It’s common to worry, “Will I regain weight once I stop Ozempic or phentermine?” Rapid rebound weight gain can happen if appetite surges back. To combat this, double down on lifestyle habits (diet and exercise) during the gap between stopping the med and getting pregnant. Some physicians may start metformin during this window as a bridge – it can help reduce insulin spikes and might blunt weight rebound a bit. Focus on high-protein, nutrient-dense eating and regular physical activity to keep your weight stable in this transition period. If you do regain a few pounds, don’t be hard on yourself – just remember you’ve already made huge progress in improving your health, and a small uptick is not the end of the world.
  
• Ensure Nutritional Status: After weight loss (especially if it was rapid), make sure you’re not nutrient-depleted going into pregnancy. Take a good prenatal vitamin, and get your labs checked for any deficiencies (common ones after intense weight loss can be iron, B12, vitamin D, etc.). Replenishing these will help both you and baby.
  
• Consult Your Healthcare Team: Have a preconception visit with your OB/GYN or healthcare provider. Let them know what medications and supplements you were taking. They can give personalized advice on how long to wait after stopping a medication and perhaps refer you to a nutritionist or maternal-fetal medicine specialist if needed. If you were on a program like Daytryp’s, also check in with that medical team – we often coordinate with patients’ OBs to create a plan for tapering meds and monitoring weight.
  
• Mind Your Mental Health: Transitioning off a weight-loss med can be emotionally challenging – these drugs can become a bit of a “security blanket.” Be kind to yourself. Some people find therapy or support groups helpful during this phase, especially if there’s anxiety about weight regain. Remember that your body is about to do an amazing thing (grow a human!), and it’s okay if your focus shifts from the scale to overall wellness.
  

Read our guide on Essential Tips for Sustainable Weight Loss – many of those tips (like mindful eating and active living) are perfect to carry you through the pre-pregnancy phase when medication is off the table.

Healthy Weight Management While TTC and During Pregnancy

So what can you do to manage weight safely while trying to conceive, or once you’re pregnant? The answer might sound old-school: nutrition, exercise, and behavioral support. But “old-school” doesn’t mean ineffective – these lifestyle approaches are the foundation of a healthy pregnancy.

• Optimize Your Pre-Pregnancy Weight (Safely): If you have some time before you plan to get pregnant, focus on losing weight through dietary changes and physical activity. Even a modest weight loss (5-10% of your body weight) can improve fertility and reduce pregnancy risks if you’re overweight. Work with a nutritionist or use reputable programs to fine-tune your eating habits. Emphasize a balanced diet rich in lean protein, high-fiber veggies, and whole grains, and moderate in carbs and healthy fats. Avoid crash diets – slow and steady wins here. Regular exercise is hugely beneficial: aim for at least 150 minutes of moderate activity per week (e.g. brisk walking, swimming, cycling) or as advised by your doc. This not only helps with weight but also conditions your body for pregnancy and relieves stress.
  
• Once Pregnant, Focus on Healthy Gain, Not Loss: As we discussed, you shouldn’t actively try to lose weight during pregnancy. However, you can focus on gaining weight in a healthy range. Depending on your starting BMI, your doctor will recommend how much weight gain is appropriate. For example, women with obesity might be advised to gain only ~10–20 pounds (or sometimes even just maintain their weight) over the pregnancy, whereas those at normal weight should gain more. Follow your OB’s guidelines on this. Eat nutrient-dense foods and listen to your hunger/fullness cues. Think of it as “growing a healthy baby” rather than dieting. Staying active during pregnancy (with your doctor’s OK) can help manage weight and reduce complications – activities like walking, prenatal yoga, swimming, or low-impact aerobics are generally great choices.
  
• Behavioral and Support Programs: Consider joining a pregnancy nutrition class or working with a health coach. Sometimes having that support makes a big difference. There are also programs (like Daytryp’s behavioral coaching components) that help with accountability and emotional aspects of eating. If emotional eating or stress eating is something you struggle with, pregnancy can throw some curveballs (hormonal mood swings and weird cravings, anyone?). Having strategies in place – like journaling, speaking with a therapist, or simply having a supportive check-in weekly – can keep you on track.
  
• Metformin (if appropriate): We mentioned metformin earlier – if you have PCOS or a history of insulin resistance, talk to your doctor about whether continuing or starting metformin in pregnancy is right for you. It’s one of the few medications that may be used for metabolic support during pregnancy, and it might help prevent excessive weight gain for some women (as well as lower the risk of gestational diabetes). Do this only under medical supervision, of course.
  
• No Other Meds or Supplements: Apart from possibly metformin, assume that no other weight loss pills are safe in pregnancy. Definitely avoid any unapproved supplements or “slimming teas,” etc. Focus on getting nutrients from real food – your baby needs those! If nausea in early pregnancy is making healthy eating hard, don’t worry too much if all you can stomach is crackers – do the best you can and stay hydrated. Things usually improve in the second trimester appetite-wise.
  

Remember, losing weight before pregnancy is one of the best things you can do for yourself and your future baby’s health – it can lower the risk of gestational diabetes, high blood pressure, big birth weight, C-section, and even future obesity for your child. So kudos to you for working on it! Once you’re pregnant, the focus shifts to maintaining those health gains. Even without weight loss meds, you’ve got the knowledge and habits to have a healthy pregnancy.

If you’re interested in non-medication aids like vitamin B12 shots for energy, see our article on Supercharge Your Metabolism with B12 Injections.

Planning Your Journey with Professional Support

Every woman’s situation is unique. The key takeaway is that weight loss medications and pregnancy don’t generally mix, but that doesn’t mean you can’t achieve a healthy weight before pregnancy or get guidance on weight management during pregnancy. If you’re considering using (or coming off) medications in preparation for pregnancy, it’s absolutely worth having a personalized plan.

At Daytryp, our providers understand both sides of this coin – the importance of achieving a healthy weight and the need to prioritize a safe pregnancy. We can work with you on a pre-conception weight loss program (for instance, a course of semaglutide followed by a planned taper), coordinate timing with your OB, and ensure you have support when transitioning off medication. Our programs incorporate nutrition and behavioral health, which become especially crucial when the meds stop. And if you’re already pregnant or breastfeeding, we’ll focus on med-free strategies and other wellness treatments appropriate for that stage.

The journey to motherhood is exciting, and we’re here to help you navigate it safely. If you’re thinking about pregnancy in the near future, come chat with our Daytryp RX team. We’ll help you create a roadmap – whether that means losing weight beforehand with medical supervision or finding pregnancy-safe alternatives to reach your goals. Your health and your baby’s health are our top priority. Reach out for a consultation to get a personalized plan, or explore our treatment pages like our Semaglutide Weight Loss Program or Tirzepatide Weight Loss Program to see how we approach medical weight loss. With the right guidance, you can set yourself up for a healthy pregnancy and beyond.

Ready to take the next step? 

Contact Daytryp RX to speak with one of our telehealth weight loss specialists and map out your plan – we’re excited to support you on your journey to baby!

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