An Australian study compared 136 women who received intralipid with 593 who did not after frozen embryo transfer.
Major birth outcomes did not differ significantly, but an early-pregnancy placental protein measurement was lower in the intralipid group.
Several add-on treatments are offered to women with repeated implantation failure or pregnancy loss during IVF. One is intralipid, an intravenous lipid emulsion. It is used in the hope that modifying immune responses might support implantation, although its effectiveness and safety remain debated.
What happens later in pregnancy among women who receive it? Are preterm birth or gestational diabetes more common?
Researchers at Flinders University and Repromed in Australia examined birth outcomes in 729 women who became pregnant after frozen embryo transfer.
They found no statistically significant differences in major pregnancy complications or birth outcomes according to intralipid exposure. Some early-pregnancy blood measurements related to placental function did differ.
Comparing 136 exposed and 593 unexposed women
The retrospective study included 729 women treated at an Australian fertility center between 2017 and 2023 whose pregnancies following frozen embryo transfer progressed to delivery after 20 weeks.
Of these, 136 received intralipid and 593 did not. The researchers compared pregnancy and birth outcomes, adjusting statistically for factors including age, body mass index, pregnancy characteristics and transfer method.
Intralipid was developed for intravenous nutrition. Some fertility centers use it as an add-on for recurrent implantation failure or recurrent pregnancy loss because of its possible effects on immune responses, including natural killer cells.
It remains unclear whether these proposed immune effects improve implantation or live birth.
Preterm birth: 16.9% versus 11.6%, without a significant difference
Preterm birth occurred in 16.9% of the intralipid group and 11.6% of the comparison group. Although numerically higher with intralipid, the difference was not statistically significant.
Mean birthweight was 3,224 g versus approximately 3,295 g, also without a significant difference.
There were no statistically significant differences in the individual outcomes of gestational diabetes, hypertensive disorders of pregnancy, fetal growth restriction, congenital anomalies or stillbirth.
Two or more pregnancy complications occurred in 5.1% of the exposed group and 1.3% of the unexposed group. However, after adjustment for age, baseline characteristics and treatment factors, the independent association between intralipid and multiple complications was not statistically significant.
Women who received intralipid tended to be older, have more previous IVF treatment and have complex fertility factors such as adenomyosis.
A simple comparison of complication rates therefore cannot establish that intralipid increased risk.
Lower early-pregnancy PAPP-A: what does it mean?
An important difference appeared in early-pregnancy blood testing.
Pregnancy-associated plasma protein A (PAPP-A) was lower in women who received intralipid. This protein is used in early prenatal screening and provides information related to placental development and function.
Median PAPP-A was 0.82 multiples of the median (MoM) in the exposed group and 0.96 MoM in the comparison group. The association with lower PAPP-A persisted after adjustment for clinical factors.
Low early-pregnancy PAPP-A can inform assessment of risks such as fetal growth restriction and pre-eclampsia.
In this study, however, the difference was not shown to translate into lower birthweight or increased fetal growth restriction. Placental growth factor (PlGF) and free beta-human chorionic gonadotropin (free β-hCG) did not differ significantly.
Further research is needed to understand the biological reason for the PAPP-A difference and its clinical significance.
This does not show that intralipid improves implantation
The distinction is essential: an absence of significant differences in birth outcomes does not establish effectiveness as a fertility treatment.
The study included women whose pregnancies progressed beyond 20 weeks, rather than everyone undergoing frozen embryo transfer. Implantation failures and early pregnancy losses were therefore excluded.
It cannot establish whether intralipid improves implantation, prevents miscarriage or ultimately raises live-birth rates.
Its retrospective observational design also cannot establish whether intralipid itself caused the observed findings.
Professional organizations including ESHRE do not recommend routine intralipid use because the available evidence is insufficient.
Birth safety matters alongside achieving pregnancy
The goal of IVF extends beyond a positive pregnancy test to sustaining pregnancy and delivering a healthy child.
The study is useful for examining pregnancy and birth outcomes in women who received intralipid.
The absence of an independent association with major complications does not prove safety for every pregnancy risk. Larger studies are needed to assess rare complications and longer-term effects on children.
Patients should discuss whether the treatment is needed, the evidence that it improves pregnancy chances, and its expected benefits and risks with their specialist.
Although this study cannot conclude that intralipid improves fertility treatment success, it contributes information about maternal and fetal outcomes after frozen embryo transfer.
This article is based on “Association of Intralipid Infusions With Birth Outcomes and First-Trimester Placental Biomarkers in Frozen Embryo Transfer Cycles: A Retrospective Cohort Study,” by researchers at Flinders University and Repromed, published online in the Australian and New Zealand Journal of Obstetrics and Gynaecology on October 20, 2026, volume 66, issue 5, e70188. DOI: 10.1111/ajo.70188.
The accompanying image was created using generative AI (ChatGPT, OpenAI); any people depicted are fictional.
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