Vitamin D during pregnancy.
Vitamin D plays a key role in calcium absorption, immune function, and fetal development. Deficiency is common in Australian women, particularly during winter months in southern latitudes. This guide reviews what the evidence actually shows about supplementation during pregnancy and breastfeeding.
What the guidelines say
The single most important fact about vitamin D thresholds is that major bodies disagree, and the disagreement has widened, not narrowed, in recent years.
All major bodies agree that vitamin D levels below 50 nmol/L are deficient and should be corrected. The evidence for this is strong.
Whether levels above 50 nmol/L (such as 75 or 100 nmol/L) provide additional benefit for pregnancy is debated. The Endocrine Society withdrew specific thresholds in 2024.
Toxicity risk is essentially absent below 125 nmol/L and does not become clinically significant until above 375 nmol/L. Standard supplementation doses are well within safe range.
Pregnancy alone is not a qualifying indication for Medicare-rebated vitamin D testing. Your GP can order the test if you have risk factors such as deeply pigmented skin, limited sun exposure, or previous deficiency.
Guideline comparison
| Body | Deficient | Insufficient | Sufficient | Optimal |
|---|---|---|---|---|
| IOM / NASEM 2011 | <30 nmol/L | 30-50 nmol/L | ≥50 nmol/L | Not defined (caution above 125 nmol/L) |
| Endocrine Society 2011 | <50 nmol/L | 50-75 nmol/L | >75 nmol/L | 100-150 nmol/L |
| Endocrine Society (updated) 2024 | Thresholds abandoned | - | - | "Unclear" - insufficient evidence for specific targets |
| ANZBMS / Osteoporosis Australia 2012 (AU) | <50 nmol/L | - | ≥50 nmol/L | ≥75 nmol/L only for osteoporosis patients |
| RANZCOG 2019 (AU) | <30 nmol/L | 30-49 nmol/L | ≥50 nmol/L | Not defined |
Australian-relevant guidelines highlighted. The Endocrine Society’s 2024 update explicitly abandoned threshold definitions.
- Ross AC et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine. J Clin Endocrinol Metab. 2011;96(1):53-58. PMID: 21118827
- Holick MF et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96(7):1911-1930. PMID: 21646368
- Demay MB et al. Vitamin D for the prevention of disease: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2024;109(8):1907-1947. PMID: 38828931
- Nowson CA et al. Vitamin D and health in adults in Australia and New Zealand: a position statement. Med J Aust. 2012;196(11):686-687. PMID: 22708765
- RANZCOG. Vitamin and mineral supplementation in pregnancy (C-Obs 25); vitamin D testing and supplementation guidance. Dosing bands: 2,000 IU/day for <30 nmol/L, 1,000 IU/day for 30-49 nmol/L.
What the research shows
Each claim below is assessed against the published clinical evidence. “Supported” means consistent RCT or high-quality observational data. “Uncertain” means suggestive evidence that remains contested. “Not supported” means the evidence does not confirm the claim.
Supported
Observational meta-analyses consistently link deficiency to higher risk of pre-eclampsia, GDM, preterm birth, and SGA. A 2023 meta-analysis (34 studies: 10 randomised trials and 24 observational) found women with levels below 25 nmol/L had about 4.3 times higher pre-eclampsia risk (AlSubai et al., SAGE Open Med 2023, PMID 38020794). Levels below 50 nmol/L carried 1.7 times higher risk.
2023 meta-analysis, PMC10666722, n=25,996; Aghajafari et al. 2013, BMJ
Your stage
Vitamin D needs shift across your journey. Building adequate stores before pregnancy is easier than correcting deficiency during pregnancy.
Preconception
1,000-2,000 IU/day (more if deficient)
Building adequate stores before pregnancy is easier than correcting deficiency during pregnancy. If you have risk factors, ask your GP about testing.
Target: ≥50 nmol/L minimum, ideally 75-100 nmol/L
Pregnancy
2,000-4,000 IU/day (guided by blood levels if tested)
The strongest evidence supports correcting deficiency. Whether targeting 75-100 nmol/L provides additional benefit is debated but is very safe. Most prenatal multivitamins contain only 200-1,000 IU, which is insufficient for many women.
Target: ≥50 nmol/L minimum
Breastfeeding
1,000-2,000 IU/day for your own health
Breastmilk contains only 5-80 IU/L of vitamin D, far below the 400 IU/day recommended for infants. Your breastfed baby needs 400 IU vitamin D drops daily, regardless of your own supplementation. Maternal doses of 6,400 IU/day can achieve equivalent infant levels, but this is not the standard recommendation.
Target: ≥50 nmol/L
Most Australian and international bodies agree that vitamin D levels below 50 nmol/L are deficient and should be corrected. Whether levels above 50 nmol/L provide additional benefit for pregnancy is genuinely debated. Aiming for 75-100 nmol/L is a reasonable goal, but we should be honest that this is based more on biological markers than proven clinical outcomes. Supplementation is very safe below 125 nmol/L. The most important step is to ensure you are not deficient, particularly if you have risk factors.
The Australian context
Vitamin D deficiency is common in Australia, with nearly a quarter of adults affected. Rates are highest in winter months in southern latitudes, where UV index drops below 3.
The 2011-12 Australian Health Survey found nearly a quarter of adults had vitamin D levels below 50 nmol/L. Rates are highest in winter months in southern latitudes (Melbourne, Hobart, Adelaide), where UV index drops below 3 and cutaneous synthesis becomes inadequate.
Women with deeply pigmented skin, those who wear covering clothing, indoor workers, and those with obesity (vitamin D is sequestered in adipose tissue) are at elevated risk. Seasonal variation is substantial in southern Australia.
Qualifying indications for Medicare-rebated vitamin D testing include osteoporosis, elevated alkaline phosphatase, hyperparathyroidism, calcium abnormalities, deeply pigmented skin, chronic lack of sun exposure, and previous deficiency diagnosis. Pregnancy alone is not a standalone indication. RANZCOG advises against routine testing in pregnancy while simultaneously recommending supplementation for at-risk women.
RANZCOG recommends 2,000 IU/day for women with levels below 30 nmol/L and 1,000 IU/day for those between 30-49 nmol/L. For women with risk factors, 2,000-4,000 IU/day is commonly recommended. In the Hollis 2011 trial, 400 IU/day often failed to reach target serum 25(OH)D levels while 4,000 IU/day reliably did, though clinical outcomes did not differ between the dose arms.
Sources
All recommendations in this guide are drawn from peer-reviewed research, clinical guidelines, and systematic reviews. Key sources are listed below.
Sources: IOM/NASEM 2011, Endocrine Society 2011 & 2024 (Demay et al., JCEM; DOI: 10.1210/clinem/dgae290), ANZBMS/OA 2012, RANZCOG C-Obs 25 (2019), Hollis et al. 2011 (JBMR; DOI: 10.1002/jbmr.463), Palacios et al. (Cochrane 2024; PMID: 39077939), Yang et al. 2024 (Nutrition Reviews, 66 RCTs), Moghib et al. 2024 (BMC Pregnancy & Childbirth, 33 RCTs), Aghajafari et al. 2013 (BMJ), Australian Health Survey 2011-12
herjourney.com.au · Health education, not medical advice
Evidence: IOM/NASEM, Endocrine Society 2024, RANZCOG C-Obs 25, Cochrane 2024 · last updated March 2026 · © Her Journey 2026