A comprehensive review on non-clinical methods to study transfer of medication into breast milk - A contribution from the ConcePTION project

Selection of a Suitable Animal Model to Evaluate Secretion of Drugs in the Human Milk: A Systematic Approach

Lack of data on drug secretion in human milk is a concern for safe use of drugs during postpartum.Clinical studies are often difficult to perform; despite substantial improvements in computational methodologies such as physiologically based pharmacokinetic modelling, there is limited clinical data to validate such models for many drugs.Various factors that are likely to impact milk to plasma ratio were identified. A literature search was performed to gather available data on milk composition, total volume of milk produced per day, milk pH, haematocrit, and renal blood flow and glomerular filtration rate in various animal models.BLAST nucleotide and protein tools were used to evaluate the similarities between humans and animals in the expression and predominance of selected drug transporters, metabolic enzymes, and blood proteins.A multistep analysis of all the potential variables affecting drug secretion was considered to identify most appropriate animal model. The practicality of using the animal in a lab setting was also considered.Donkeys and goats were identified as the most suitable animals for studying drug secretion in milk.

Isolation and characterization of mammary epithelial cells derived from Göttingen Minipigs: A comparative study versus hybrid pig cells from the IMI-ConcePTION Project

The value of pig as "large animal model" is a well-known tool for translational medicine, but it can also be beneficial in studying animal health in a one-health vision. The ConcePTION Project aims to provide new information about the risks associated with medication use during breastfeeding, as this information is not available for most commonly used drugs. In the IMI-Conception context, Göttingen Minipigs have been preferred to hybrid pigs for their genetic stability and microbiological control. For the first time, in the present research, three primary cell cultures of mammary epithelial cells were isolated and characterized from Göttingen Minipigs (mpMECs), including their ability to create the epithelial barrier. In addition, a comparative analysis between Göttingen Minipigs and commercial hybrid pig mammary epithelial cells (pMECs) was conducted. Epithelial markers: CKs, CK18, E-CAD, ZO-1 and OCL, were expressed in both mpMECs and pMECs. RT2 Profiler PCR Array Pig Drug Transporters showed a similar profile in mRNA drug transporters. No difference in energy production under basal metabolic condition was evidenced, while under stressed state, a different metabolic behaviour was shown between mpMECs vs pMECs. TEER measurement and sodium fluorescein transport, indicated that mpMECs were able to create an epithelial barrier, although, this turned out to be less compact than pMECs. By comparing mpMECs with mammary epithelial cells isolated from Hybrid pigs (pMECs), although both cell lines have morphological and phenotypic characteristics that make them both useful in barrier studies, some specific differences exist and must be considered in a translational perspective.

Using a Cognitive Aid to Improve Confidence in Counseling Regarding Current Anesthesia-Related Breastfeeding Recommendations

PURPOSE

Although most anesthetic drugs are classified as compatible with breastfeeding, literature shows that anesthesia providers routinely advise patients to discard milk when receiving all types of anesthesia. The purpose of this project was to determine if a multimodal educational module and cognitive aid improved student registered nurse anesthetists' knowledge and confidence to counsel lactating patients on current anesthesia-related recommendations.

DESIGN

This project used a pre-experimental one-group, pretest and post-test design.

METHODS

Preintervention and postintervention surveys measured knowledge and confidence to counsel lactating patients scheduled to receive anesthesia.

FINDINGS

Significant improvement in knowledge and confidence after the intervention were noted.

CONCLUSIONS

A multimodal educational session and cognitive aid improved student registered nurse anesthetists' knowledge about current anesthesia-related breastfeeding recommendations and their confidence in counseling these patients. Wider use of this educational module with the cognitive aid has the potential to positively impact breastfeeding patients and their children.

Evaluation of the Epithelial Barrier Integrity in Primary Cultures of Pig Mammary Epithelial Cells

A major feature of epithelial and endothelial cells is the creation of biological barriers able to protect the body against stressors that could compromise homeostasis. The ability to characterize biological barriers in vitro is an important study tool especially used for the intestinal barrier, the blood-brain barrier, and the lung barrier. The strength and integrity of biological barriers may be assessed by the measurement of the transepithelial/transendothelial electrical resistance (TEER) that reflects the ionic conductance of the paracellular pathway. The TEER measurement is a quantitative, non-invasive, highly useful, and representative method that must be strictly standardized. Here we describe a quantitative protocol to assess the mammary epithelial barrier integrity by combining the TEER measurement with a test for studying the passage of the sodium fluorescein, that is, a hydrophilic paracellular marker. Being the swine species an excellent translational model, primary cultures of mammary epithelial cells, isolated from hybrid pig tissue collected at slaughterhouse, are used.

Evaluating strength of recommendations for commonly administered medications in lactating women

OBJECTIVE

To characterize the data on medications for lactating people in the LactMed database and evaluate the strength of the data for the most commonly administered medications in lactating women.

METHODS

A retrospective analysis of all medications in the LactMed database in 12/2020 was performed. Each medication was classified into one of three categories: absent data, minimal-moderate data, strong data pertaining to safety in lactation. No data was defined as no available research studies associated with the medication. Minimal-moderate data was defined as absent research studies in one or more of the four LactMed categories: maternal drug levels, infant drug levels, effects on infants, effects on lactation, or if data was limited to a case report or observational study. Strong data was classified as availability of research studies in all four LactMed categories with data derived from pharmacokinetic/pharmacodynamic, cohort, case control, or randomized control studies. Additionally, the most commonly used medications in lactating women as defined by prior literature were analyzed for strength of data.

RESULTS

1408 medications were evaluated: 714 (51%) had no associated data, 664 (47%) had minimal-moderate data, and 30 (2%) had strong data. Maternal drug level category had the highest proportion of rigorous supportive data while the effect on lactation category had the least supportive data. Of the most common mediations used in lactating women, sex hormones (contraception) and the nervous system medication classes had the most robust supportive data while respiratory, blood forming organs, and galactogogues had the weakest supportive data.

CONCLUSION

There is significant variability and dearth in the quality of data guiding recommendations for use of medications in lactation providing numerous opportunities for research.

Sensitive and rapid method for the quantitation of amoxicillin in minipig plasma and milk by LC-MS/MS: A contribution from the IMI ConcePTION project

The IMI project ConcePTION was launched to fill the knowledge gap of using medicines during pregnancy and lactation. To achieve this goal, several studies are being conducted, including the bioanalysis of amoxicillin in minipig plasma and milk. A high-throughput, robust and reliable liquid chromatography tandem mass spectrometry method was developed and validated according to FDA and EMA guidelines to determine the concentrations of amoxicillin in a large number of minipig plasma and milk samples. Chromatographic separation was achieved on a Luna® Omega Polar C18, 1.6 μm, 100 × 2.1 mm column, with a mobile phase consisting of 0.1% formic acid in water and acetonitrile. Mass spectrometry used in a positive ionization mode and the transitions m/z 366.1 → 349.2 was selected to monitor amoxicillin, while m/z 370.1 → 114.15 was selected for the stable isotope labelled internal standard. This method features a linear quantification range of 10 ng/mL - 10 μg/mL, recovery of not less than 94.1%, a single sample extraction method for both plasma and milk matrices, and an analysis runtime of 5 min.

Predicting Chemotherapy Distribution into Breast Milk for Breastfeeding Women Using a Population Pharmacokinetic Approach

BACKGROUND AND OBJECTIVE

Information on the distribution of chemotherapeutic drugs to breast milk is scarce, and reports are limited to small sample sizes. Anecdotal pharmacokinetic data have typically been acquired from lactating but non-breastfeeding patients who collect breast milk by means of an expression pump, which might not necessarily be representative for a breastfeeding population due to differences in milk production. Consequently, little is known about the variability of chemotherapy distribution to breast milk and the effect of milk production on the distribution of chemotherapy to breast milk. Our aim was to predict chemotherapy distribution to breast milk in a more realistic breastfeeding population and evaluate the effect of discarding breast milk on the potential chemotherapy exposure in infants.

METHODS

We developed a population pharmacokinetic model that described the breast milk production and the chemotherapy distribution to breast milk of a non-breastfeeding population, linked it to plasma pharmacokinetics, and extrapolated this to a breastfeeding population.

RESULTS

We found that cumulative relative infant doses (RID) were higher than 10% for cyclophosphamide and doxorubicin and approximately 1% for paclitaxel. Simulations allowed us to predict the cumulative RID and its variability in the population for patients with different milk productions and the amount of breast milk that has to be discarded to reach cumulative RIDs below 1%, 0.1%, and 0.01%. Discarding 1-2, 3-6, and 0-1 days of breast milk (depending on the milk production of the patient) resulted in cumulative RID below 1% for cyclophosphamide, doxorubicin, and paclitaxel, respectively.

CONCLUSION

Our results may help clinicians to derive the optimal breast milk discarding strategy for an individual patient that wants to breastfeed during chemotherapy and minimize chemotherapy exposure in their infants.

Safety of medicines during breastfeeding - from case report to modeling : A contribution from the ConcePTION project

INTRODUCTION

Despite many research efforts, current data on the safety of medicines during breastfeeding are either fragmented or lacking, resulting in restrictive labeling of most medicines. In the absence of pharmacoepidemiologic safety studies, risk estimation for breastfed infants is mainly derived from pharmacokinetic (PK) information on the medicine. This manuscript provides a description and a comparison of the different methodological approaches that can yield reliable information on medicine transfer into human milk and the resulting infant exposure.

AREA COVERED

Currently, most information on medicine transfer in human milk relies on case reports or traditional PK studies, which generate data that can hardly be generalized to the population. Some methodological approaches, such as population PK (popPK) and physiologically-based PK (PBPK) modeling, can be used to provide a more complete characterization of infant medicine exposure through human milk and simulate the most extreme situations, while decreasing the burden of sampling in breastfeeding women.

EXPERT OPINION

PBPK and popPK modeling are promising approaches to fill the gap of knowledge in medicine safety in breastfeeding, as illustrated with our escitalopram example.

Generic Workflow to Predict Medicine Concentrations in Human Milk Using Physiologically-Based Pharmacokinetic (PBPK) Modelling-A Contribution from the ConcePTION Project

Women commonly take medication during lactation. Currently, there is little information about the exposure-related safety of maternal medicines for breastfed infants. The aim was to explore the performance of a generic physiologically-based pharmacokinetic (PBPK) model to predict concentrations in human milk for ten physiochemically diverse medicines. First, PBPK models were developed for "non-lactating" adult individuals in PK-Sim/MoBi v9.1 (Open Systems Pharmacology). The PBPK models predicted the area-under-the-curve (AUC) and maximum concentrations (C_max) in plasma within a two-fold error. Next, the PBPK models were extended to include lactation physiology. Plasma and human milk concentrations were simulated for a three-months postpartum population, and the corresponding AUC-based milk-to-plasma (M/P) ratios and relative infant doses were calculated. The lactation PBPK models resulted in reasonable predictions for eight medicines, while an overprediction of human milk concentrations and M/P ratios (>2-fold) was observed for two medicines. From a safety perspective, none of the models resulted in underpredictions of observed human milk concentrations. The present effort resulted in a generic workflow to predict medicine concentrations in human milk. This generic PBPK model represents an important step towards an evidence-based safety assessment of maternal medication during lactation, applicable in an early drug development stage.

Computational Approach to Drug Penetration across the Blood-Brain and Blood-Milk Barrier Using Chromatographic Descriptors

Drug penetration through biological barriers is an important aspect of pharmacokinetics. Although the structure of the blood-brain and blood-milk barriers is different, a connection can be found in the literature between drugs entering the central nervous system (CNS) and breast milk. This study was created to reveal such a relationship with the use of statistical modelling. The basic physicochemical properties of 37 active pharmaceutical compounds (APIs) and their chromatographic retention data (TLC and HPLC) were incorporated into calculations as molecular descriptors (MDs). Chromatography was performed in a thin layer format (TLC), where the plates were impregnated with bovine serum albumin to mimic plasma protein binding. Two columns were used in high performance liquid chromatography (HPLC): one with immobilized human serum albumin (HSA), and the other containing an immobilized artificial membrane (IAM). Statistical methods including multiple linear regression (MLR), cluster analysis (CA) and random forest regression (RF) were performed with satisfactory results: the MLR model explains 83% of the independent variable variability related to CNS bioavailability; while the RF model explains up to 87%. In both cases, the parameter related to breast milk penetration was included in the created models. A significant share of reversed-phase TLC retention values was also noticed in the RF model.

Maternal amoxicillin affects piglets colon microbiota: microbial ecology and metabolomics in a gut model

Abstract

The first weeks of life represent a crucial stage for microbial colonization of the piglets’ gastrointestinal tract. Newborns’ microbiota is unstable and easily subject to changes under stimuli or insults. Nonetheless, the administration of antibiotics to the sow is still considered as common practice in intensive farming for pathological conditions in the postpartum. Therefore, transfer of antibiotic residues through milk may occurs, affecting the piglets’ colon microbiota. In this study, we aimed to extend the knowledge on antibiotic transfer through milk, employing an in vitro dedicated piglet colon model (MICODE—Multi Unit In vitro Colon Model). The authors’ focus was set on the shifts of the piglets’ microbiota composition microbiomics (16S r-DNA MiSeq and qPCR—quantitative polymerase chain reaction) and on the production of microbial metabolites (SPME GC/MS—solid phase micro-extraction gas chromatography/mass spectrometry) in response to milk with different concentrations of amoxicillin. The results showed an effective influence of amoxicillin in piglets’ microbiota and metabolites production; however, without altering the overall biodiversity. The scenario is that of a limitation of pathogens and opportunistic taxa, e.g., Staphylococcaceae and Enterobacteriaceae, but also a limitation of commensal dominant Lactobacillaceae, a reduction in commensal Ruminococcaceae and a depletion in beneficial Bifidobactericeae. Lastly, an incremental growth of resistant species, such as Enterococcaceae or Clostridiaceae, was observed. To the authors’ knowledge, this study is the first evaluating the impact of antibiotic residues towards the piglets’ colon microbiota in an in vitro model, opening the way to include such approach in a pipeline of experiments where a reduced number of animals for testing is employed.

Key points

• Piglet colon model to study antibiotic transfer through milk.

• MICODE resulted a robust and versatile in vitro gut model.

• Towards the “3Rs” Principles to replace, reduce and refine the use of animals used for scientific purposes (Directive 2010/63/UE).

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-022-12223-3.

Information Needs and Counseling Preferences among Potential Users of the Future Teratology Information Service in Belgium: A Cross-Sectional Study Involving the Public and Healthcare Professionals

A Teratology Information Service (TIS) does not exist in Belgium yet but will hopefully be established soon. To prepare for this, we aimed to provide insight into the information needs and counseling preferences of the Belgian public and healthcare professionals (HCPs) regarding medication use in pregnancy and breastfeeding. A cross-sectional study using two anonymous, online surveys disseminated via social media, websites, and newsletters addressing Dutch and French-speaking individuals (≥18 years) and licensed HCPs was performed between June and September 2020. Ethics approval and informed consent were obtained. In total, 1508 public survey respondents (98% women) and 702 HCPs participated. Information needs on perinatal medication use were ubiquitous among both groups, and for which they often relied on patient information leaflets or the product information and online fora. Conflicting information on this topic regularly occurs and complicates HCPs’ duties. Women and HCPs assigned an important role to a TIS, both in terms of providing evidence-based information (via a website or app) and being accessible to be contacted in case of questions (by phone or via e-mail or chat). In conclusion, a TIS would be warmly welcomed by women and HCPs in Belgium and should ideally be established soon to address current information needs regarding perinatal medication use and to contribute to research in this field.

Human milk microbiota: what did we learn in the last 20 years?

Human milk (HM) is the gold standard for infant nutrition during the first months of life. Beyond its nutritional components, its complex bioactive composition includes microorganisms, their metabolites, and oligosaccharides, which also contribute to gut colonization and immune system maturation. There is growing evidence of the beneficial effects of bacteria present in HM. However, current research presents limited data on the presence and functions of other organisms. The potential biological impacts on maternal and infant health outcomes, the factors contributing to milk microbes' variations, and the potential functions in the infant's gut remain unclear. This review provides a global overview of milk microbiota, what the actual knowledge is, and what the gaps and challenges are for the next years.

Development of a Generic Physiologically-Based Pharmacokinetic Model for Lactation and Prediction of Maternal and Infant Exposure to Ondansetron via Breast Milk

Ondansetron is commonly used in breastfeeding mothers to treat nausea and vomiting. There is limited information in humans regarding safety of ondansetron exposure to nursing infants and no adequate study looking at ondansetron pharmacokinetics during lactation. We developed a generic physiologically-based pharmacokinetic lactation model for small molecule drugs and applied this model to predict ondansetron transfer into breast milk and characterize infant exposure. Drug-specific model inputs were parameterized using data from the literature. Population-specific inputs were derived from a previously conducted systematic literature review of anatomic and physiologic changes in postpartum women. Model predictions were evaluated using ondansetron plasma and breast milk concentration data collected prospectively from 78 women in the Commonly Used Drugs During Lactation and infant Exposure (CUDDLE) study. The final model predicted breast milk and plasma exposures following a single 4 mg dose of intravenous ondansetron in 1,000 simulated women who were 2 days postpartum. Model predictions showed good agreement with observed data. Breast milk median prediction error (MPE) was 18.4% and median absolute prediction error (MAPE) was 53.0%. Plasma MPE was 32.5% and MAPE was 43.2%. The model-predicted daily and relative infant doses were 0.005 mg/kg/day and 3.0%, respectively. This model adequately predicted ondansetron passage into breast milk. The calculated low relative infant dose indicates that mothers receiving ondansetron can safely breastfeed. The model building blocks and population database are open-source and can be adapted to other drugs.

Re-orienting anti-malarial drug development to better serve pregnant women

Malaria is one of the most serious infectious diseases affecting predominantly low- and middle-income countries, where pregnant women are among the populations at risk. There are limited options to prevent or treat malaria in pregnancy, particularly in the first trimester, and existing ones may not work optimally in areas where the threat of drug resistance is rising. As malaria elimination is a key goal of the global health community, the inclusion of pregnant women in the adult population to protect from malaria will be key to achieving success. New, safe, and effective options are needed but it can take decades of evidence-gathering before a medicine is recommended for use in pregnancy. This is because pregnant women are typically not included in pre-registration clinical trials due to fear of causing harm. Data to support dosing and safety in pregnancy are subsequently collected in post-licensure studies. There have been growing calls in recent years that this practice needs to change, amplified by the COVID-19 pandemic and increasing public awareness that newly developed medicines generally cannot be administered to pregnant women from the onset. The development of new anti-malarials should ensure that data informing their use in pregnancy and breastfeeding are available earlier. To achieve this, a mindset change and a different approach to medications for pregnant women are needed. Changes in non-clinical, translational, and clinical approaches in the drug development pathway, in line with recent recommendations from the regulatory bodies are proposed in this Comment. The new approach applies to any malaria-endemic region, regardless of the type of Plasmodium responsible for malaria cases. By incorporating intentional and systematic data collection from pre-registration stages of development through post-licensure, it will be possible to inform on the benefit/risk balance of a new anti-malarial earlier and help ensure that the needs of pregnant individuals are addressed in a more timely and equitable manner in the future.

Application of Physiologically Based Pharmacokinetic Modeling to Evaluate the Drug-Drug and Drug-Disease Interactions of Apatinib

Aim: Apatinib is an orally administered vascular epidermal growth factor receptor (VEGFR)-tyrosine kinase inhibitors approved for the treatment of advanced gastric adenocarcinoma or gastric esophageal junction adenocarcinoma. Apatinib is predominantly metabolized by CYP3A4/5, followed by CYP2D6. The present study aimed to evaluate the potential drug–drug interaction (DDI) and drug–disease interaction (DDZI) risks of apatinib in Chinese volunteers.

Methods: Modeling and simulation were conducted using Simcyp Simulator. The input parameters required for modeling were obtained from literature research or experiments. Then, the developed physiologically based pharmacokinetic (PBPK) models were applied to evaluate single-dose DDI potential in Chinese healthy volunteers with weak and moderate CYP3A inhibitors, strong CYP2D6 inhibitors, as well as CYP3A4 inducers. The DDZI potential was also predicted in patients with hepatic or renal impairment.

Results: The developed PBPK models accurately assessed apatinib pharmacokinetics following single-dose administration in Chinese healthy volunteers and cancer patients. The DDI simulation showed 2–4-fold changes in apatinib exposures by moderate CYP3A4 inhibitors and CYP3A4 inducers. A moderate increase of apatinib exposure (1.25–2-fold) was found with strong CYP2D6 inhibitor. In the DDZI simulation with hepatic impairment, the AUC of apatinib was significantly increased by 2.25-fold and 3.04-fold for Child–Pugh B and Child–Pugh C, respectively, with slightly decreased C_max by 1.54 and 1.67-fold, respectively.

Conclusion: The PBPK models developed in the present study would be highly beneficial to quantitatively predict the pharmacokinetic changes of apatinib under different circumstances, which might be difficult to evaluate clinically, so as to avoid some risks in advance.

Prediction of drug concentrations in milk during breastfeeding, integrating predictive algorithms within a physiologically-based pharmacokinetic model

There is a risk of exposure to drugs in neonates during the lactation period due to maternal drug intake. The ability to predict drugs of potential hazards to the neonates would be useful in a clinical setting. This work aimed to evaluate the possibility of integrating milk-to-plasma (M/P) ratio predictive algorithms within the physiologically-based pharmacokinetic (PBPK) approach and to predict milk exposure for compounds with different physicochemical properties. Drug and physiological milk properties were integrated to develop a lactation PBPK model that takes into account the drug ionization, partitioning between the maternal plasma and milk matrices, and drug partitioning between the milk constituents. Infant dose calculations that take into account maternal and milk physiological variability were incorporated in the model. Predicted M/P ratio for acetaminophen, alprazolam, caffeine, and digoxin were 0.83 ± 0.01, 0.45 ± 0.05, 0.70 ± 0.04, and 0.76 ± 0.02, respectively. These ratios were within 1.26-fold of the observed ratios. Assuming a daily milk intake of 150 ml, the predicted relative infant dose (%) for these compounds were 4.0, 6.7, 9.9, and 86, respectively, which correspond to a daily ingestion of 2.0 ± 0.5 mg, 3.7 ± 1.2 µg, 2.1 ± 1.0 mg, and 32 ± 4.0 µg by an infant of 5 kg bodyweight. Integration of the lactation model within the PBPK approach will facilitate and extend the application of PBPK models during drug development in high-throughput screening and in different clinical settings. The model can also be used in designing lactation trials and in the risk assessment of both environmental chemicals and maternally administered drugs.

Development of a Pig Mammary Epithelial Cell Culture Model as a Non-Clinical Tool for Studying Epithelial Barrier-A Contribution from the IMI-ConcePTION Project

Simple Summary

The information about the risks related to the use of medication during breastfeeding is lacking for most commonly used drugs. The ConcePTION project aims to fill this gap using multiple approaches. Within the project, the pig has been selected as the most appropriate in vivo animal model. In agreement with the application of the “3Rs” principle (Replacement, Reduction and Refinement) and international legislations, the present paper reports the establishment of cellular lines of porcine mammary epithelial cells as a valid tool to study the mammary epithelial barrier function in vitro.

Abstract

The ConcePTION project aims at generating further knowledge about the risks related to the use of medication during breastfeeding, as this information is lacking for most commonly used drugs. Taking into consideration multiple aspects, the pig model has been considered by the consortium as the most appropriate choice. The present research was planned to develop an efficient method for the isolation and culture of porcine Mammary Epithelial Cells (pMECs) to study the mammary epithelial barrier in vitro. Mammary gland tissues were collected at a local slaughterhouse, dissociated and the selected cellular population was cultured, expanded and characterized by morphology, cell cycle analysis and immunophenotyping. Their ability to create a barrier was tested by TEER measurement and sodium fluorescein transport activity. Expression of 84 genes related to drug transporters was evaluated by a PCR array. Our results show that primary cells express epithelial cell markers: CKs, CK18, E-Cad and tight junctions molecules ZO-1 and OCL. All the three pMEC cellular lines were able to create a tight barrier, although with different strengths and kinetics, and express the main ABC and SLC drug transporters. In conclusion, in the present paper we have reported an efficient method to obtain primary pMEC lines to study epithelial barrier function in the pig model.

Phthalate Exposure Pattern in Breast Milk within a Six-Month Postpartum Time in Southern Taiwan

Di-(2-ethylhexyl) phthalate (DEHP), a common plasticizer, has been detected in breast milk in many countries; however, whether phthalate metabolite concentration and the detection rate in breast milk change postpartum is still unknown. We measured phthalate metabolite concentrations in breast milk in the first 6 months postpartum in women enrolled in the E-Da hospital from January to July 2017. A total of 56 breastfeeding mothers and 66 samples were included in this study. We analyzed the samples’ concentration of eight phthalate metabolites using liquid chromatography mass spectrometry. The concentration of mono-2-ethylhexyl phthalate (MEHP) was significantly higher in the first month, and then decreased over time. The detection rate of ono-isobutyl phthalate (MiBP) and mono-n-butyl phthalate (MBP) was low in the first month and then increased over time. Compared with a previous study published in 2011, the levels of MEHP and MiBP in breast milk were much lower in the present study, suggesting an increased awareness of the health risks of phthalate exposure after a food scandal occurred in Taiwan. This study provides information for evaluating newborns’ exposure to different kinds of phthalate through human milk in the postpartum period.