Prenatal Nutrition: What Your Doc Didn't Tell You

By Lena DeGloma,

I’m sure you have seen all kinds of articles on the importance of prenatal nutrition since you’ve been pregnant – often hitting you over the head with the same old not-so-exciting information about eating a balanced diet. You’ve heard it all before. But I’m willing to bet that most, if not all, of these 5 things will surprise you or teach you something you weren’t already aware of.

How can fish oil supplements impact when you will go into labor? A deficiency in which nutrient can lead to stretch marks? How can your prenatal nutrition influence the likelihood that you will be given intravenous antibiotics in labor and also affect your baby’s chances of having eczema, allergies, and asthma? Read on to find out the answers to these questions plus a few more. Be sure to talk with your midwife or doctor before making any changes to your diet or supplements.

1. Taking fish oil (rich in DHA and EPA) during the final weeks of pregnancy may delay the onset of labor. You have probably already been told all about the benefits of prenatal DHA and/or fish oil for baby’s brain and eye development. And there are a variety of benefits to taking this supplement. However, in the final weeks of pregnancy you may want to temporarily back off of this one. Don’t worry if there is some in your prenatal multivitamin – it is usually a negligible amount in multis so you shouldn’t stop taking your prenatals. More importantly, you may want to stop taking separate high-dose fish oil DHA/EPA supplements in your final weeks. However, don’t forget to resume postpartum if you are breastfeeding as these fatty acids can continue to reach your baby and help grow her brain via your milk.

So, how can fish oil delay the onset of labor? The quick simplified version is that some of the most important chemicals in triggering the labor process (aside from the hormone oxytocin) are little fatty-acid based molecules called prostaglandins that get released locally by your uterus and cervix. There are lots of different types of prostaglandins and some can trigger smooth muscle cramping (think uterine contractions) while others have a more anti-inflammatory and relaxing effect on smooth muscle (among many other actions). The types of fats we get in out diet influence the relative amounts of each of these types of prostaglandins that our body makes – and the fatty acids found in fish oil (especially the EPA) are the precursors for the smooth muscle relaxing type of prostaglandins (not what we need to get labor going unfortunately!).

If you know you are at risk for preterm labor, fish oil may be very protective to continue taking at least until you reach full-term (37-38 weeks). However, in general, you want to avoid taking this too far into pregnancy to avoid delaying the onset of labor too far past your due date and risking the possibility of a medical induction. Also, continuing to take very high doses in the final weeks and days before you give birth carries the risk of thinning your blood and contributing to excessive bleeding during birth or postpartum. I generally recommend stopping fish oil supplements temporarily sometime between 36-38 weeks until after you give birth. However, during that time you can continue to eat moderate amounts of healthy low-toxin fatty fish as a part of your normal diet, such as wild Alaskan salmon, Pacific sardines, Atlantic mackerel (not king mackerel), anchovies, herring, and US farmed rainbow trout.

2. You are probably not getting enough vitamin D, even in your prenatal vitamins. The Institute of Medicine recommends that pregnant women consume only 400-600 IU of vitamin D per day. However, a recent study published in the American Journal of Obstetrics and Gynecology compared pregnant women taking 4,000 IU per day to 2,000 IU per day and found greater benefits in pregnant women taking 4,000 IU per day. Specifically, they found reduced rates of preterm labor, hypertension, preeclampsia, and infections, as well as improved vitamin D stores in the baby. In addition, there is evidence that adequate vitamin D levels during pregnancy increase the likelihood that the baby will be a normal size for gestational age at birth and have better skeletal integrity.

Most prenatal vitamins contain between 600-1,000 IU of vitamin D per day (and I have never seen one with over 2,000 IU). While this may be enough to prevent a frank deficiency, you may need to supplement with extra vitamin D to get optimal levels. While you can get some vitamin D from food sources (such as cod liver oil, egg yolks and cheese), most of our vitamin D is produced in our skin in response to UV light and most of us are not getting what we need from the sun (for a variety of reasons) so nearly everyone in this part of the world is found to have suboptimal levels if they are not supplementing.

Be sure you are taking your vitamin D with meals since it is a fat soluble vitamin. The best form is D3 or cholecalciferol. And postpartum, if you are breastfeeding, there is new evidence that that taking 6,400 IU of vitamin D3 per day allows breastfeeding parents to pass adequate levels onto their babies via their breastmilk (this was shown to be comparable to directly supplementing the baby with the recommended 400 IU per day dose).

3. Getting probiotics in your diet can reduce the likelihood that your baby will develop allergies, asthma, eczema, and some autoimmune diseases (it may also reduce the likelihood that you’ll be one of the 15-30% of women who test positive for group beta strep bacteria in their vagina and as a result given IV antibiotics during labor). Over the past decade we have seen an explosion of research and new evidence on the importance of the human microbiome to many aspects of our health. In other words, the balance of the ecosystem of “bugs” (microorganisms) that live in our guts (and all over our body) are critical to our health – and our baby’s microbiome is primarily established via exposure to our microorganisms through vaginal birth and breastfeeding (although it can be restored in a variety of ways if one or neither of these are possible for you).

During pregnancy it is critical that we keep this ecosystem in our gut well-nourished and in balance. Studies find that women who supplement with probiotics during the third trimester have babies who are less likely to be afflicted with so-called atopic conditions such as allergies, asthma and eczema as well as some autoimmune diseases such as inflammatory bowel disease. There is also evidence that probiotics taken during pregnancy may reduce the chances of gestational diabetes, fetal overgrowth, and preterm labor (by reducing incidence of vaginal and urinary tract infections which are known to trigger preterm labor).

Probiotics can be ingested regularly via fermented foods such as sauerkraut, kimchi, yogurt, kefir, traditionally fermented veggies, water kefir soda, other fermented drinks like beet kvass, and more. Probiotic capsules should contain a mix of a variety of lactobacilli and bifidus species at a dose of about 20-100 billion CFUs per day (depending on whether you have signs that your flora is already out of balance). Also, if you want to avoid feeding the “bad” bacteria then reduce all sugars and refined carbohydrates (like white flour products) in your diet as much as possible. And don’t forget to feed your friendly microorganisms with prebiotic-rich foods like asparagus, leeks, onions, garlic, Jerusalem artichokes, jicama, burdock root, chicory root, and dandelion greens.

4.  Your body may not be properly metabolizing folic acid (found in most prenatal vitamins and fortified in many foods) so you may need to take a different form of this critical B vitamin. It is pretty well-known that vitamin B9 (also known as folate and folic acid) is critical in pregnancy to help prevent certain types of birth defects. However, our bodies can’t actually use the folic acid (synthetic form) or folate (the form found naturally in foods) until it converts it through a series of chemical reactions into the active form of the vitamin known as 5-10-methylenetetrahydrofolate (5-10-MTHF for short).

Our body needs an enzyme called MTHFR in order to make this conversion and about 15-60% of the population has a minor genetic mutation that causes the MTHFR enzyme to be less effective at doing its job. Most of us who have the genetic mutation still have some functionality of the enzyme but just can’t convert quite as much, while a small percentage have very little functionality of this enzyme; it depends on whether we have one or two copies of the associated defective genes. Now some prenatal vitamins are being formulated to contain the activated or methylated version of folate (usually labeled as methylfolate, Metafolin, L-5-MTHF, or 5-MTHF) instead of folic acid.

You can get a simple blood test to find out if you have this genetic mutation, or you can just use the activated version of folate even if you don’t know if you have the mutation. It won’t hurt to take this form regardless of whether your MTHFR enzyme is working well. If you do know you have the MTHFR mutation (or if you have a family history of congenital anomalies, autism, down’s syndrome, schizophrenia, bipolar disorder, gestational diabetes, pre-eclampsia, or elevated levels of homocysteine in your blood) then you should consider taking the methylated version of folate at a dose of 1,000 mcg (1 mg) per day (the dose for normal pregnancy of folic acid is 600 mcg per day).

Also, take note that vitamin B12 uses the same enzyme so you’ll want to look for methylated B12 (labeled methylcobalamin instead of cyanocobalamin) in your supplements as well. Even though many of the well-known benefits of folate are based on starting to take it before you are pregnant through the first trimester, there is newer evidence that getting adequate levels through the rest of pregnancy may reduce rates of language delays and autism in the baby.

5. If you are getting a lot of stretch marks you might be zinc deficient. There is no evidence that using creams, oils, or lotions topically on your belly during pregnancy will reduce or prevent stretch marks (although they may help with itching caused by your stretching skin). However, getting adequate levels of zinc in your diet may just help. The reason inadequate levels of zinc may show up in your body as stretch marks is that this mineral is critical for tissue integrity. It is also important for your baby’s immune system development (and your immune functioning) as well as cell replication and DNA synthesis.

If you have noticed you are getting stretch marks you might take this as a sign to assess your zinc status. How much is in your prenatal vitamins? Do you have little white marks on your fingernails (sign of deficiency)? What is your diet like? The standard recommend dose for pregnancy is 11 mg per day, but if you have stretch marks or other signs you might need a bit more. A number of studies have found benefits to taking 15-25 mg per day. Make sure that if your prenatal vitamin (or any mineral supplement you may be taking) contains these slightly higher levels of zinc (15-25 mg) that it also contains about 2 mg per day of copper (to prevent a zinc-induced copper deficiency).

Also, zinc and iron compete with each other so if you are taking extra zinc beyond what is in your prenatal vitamin, be sure to take it at least a few hours apart from your prenatals or any other iron supplements (and take with food to avoid nausea). Oysters are by far the single best food source of zinc (just avoid the raw ones while pregnant), but seafood in general (especially crab), nuts/seeds (especially pumpkin seeds, sesame seeds/tahini and peanuts), egg yolks, beans/legumes, and shiitake mushrooms are also good sources.

Of course, talk with your doctor or midwife before making any dietary or supplement changes. If you would like to learn more about prenatal nutrition, look into my childbirth education classes at Bend and Bloom. Students receive my prenatal nutrition guide to download (among dozens of other childbirth resources) and learn a lot more of the most up to date, evidence-based information and practical techniques for coping with childbirth, avoiding unnecessary medical interventions, newborn care, postpartum care, and breastfeeding. The next class begins on March 17th.  

Lena DeGloma, has a master of science in clinical herbal medicine and is also a licensed massage therapist, certified birth doula, certified lactation counselor, and certified childbirth educator. She has been practicing for 10 years and is the founder of Red Moon Wellness in Park Slope.