A Multicenter, Postmarketing Study Evaluating the Concentration of Cimzia® in Mature Breast Milk of Lactating Mothers

The primary objectives of this study are to assess whether there is transfer of Certolizumab Pegol (CZP) into breast milk of lactating mothers who are receiving an established dosing regimen of CZP by evaluating the concentration of CZP in mature breast milk, and to calculate the daily infant dose of maternal CZP.

The study will only include women who are receiving treatment with Certolizumab Pegol (CZP) for an approved indication in accordance with their treating physician, although this study is non-interventional regarding treatment with CZP, it is considered interventional due to the collection of breast milk from the lactating mothers.

Eligibility Criteria:
Inclusion Criteria:

* An IRB/IEC approved written Informed Consent form for participation of the maternal subject and her infant (for collection of infant demographic and AE data) is signed and dated by the subject. Where applicable, the written Informed Consent form with respect to the infant is also signed and dated by the holder of parental rights as designated by the maternal subject
* Subject is considered reliable and capable of adhering to the protocol and visit schedule according to the judgment of the Investigator
* Subject is female and at least 18 years of age at the time of providing consent
* Subject has delivered term infant(s) (at least 37 weeks gestation)
* Subject is being treated with Certolizumab Pegol (CZP) per the current approved prescribing information
* The decision to treat with CZP or to breastfeed is made independently from and prior to the subject consenting to participate in this study
* Subject agrees to use only the emollient or nipple cream provided by the Sponsor for use during the Sampling Period as described per protocol
* Subject is at least 6 weeks postpartum
* Subject is on an established dosing regimen of CZP (at least the third dose of CZP since starting/restarting CZP)

Exclusion Criteria:

* Subject is pregnant or plans to become pregnant during the study
* Subject is taking a prohibited medication or has taken a prohibited medication Note: any subjects requiring antibiotics must be discussed with the Medical Monitor prior to enrollment
* Subject has history of chronic alcohol abuse or drug abuse in the last year
* In subjects who intend to breastfeed, the infant has any abnormality noted on physical examination that, in the opinion of the Investigator, may jeopardize or compromise the subject's ability to participate in this study
* Subject has any medical, obstetrical or psychiatric condition that, in the opinion of the Investigator, can jeopardize or would compromise the subject's ability to participate in this study or the outcome of the pregnancy (as applicable). Note: subjects with mastitis infection should not have samples collected until the infection is completely resolved
* Subject has history of breast implants, breast augmentation, or breast reduction surgery
* Subject has previously participated in this study
* Subject has participated in a study of an investigational medicinal product (IMP) (or a medical device) within the previous 30 days or 5 half-lives (whichever is longer) prior to Screening or is currently participating in another study of an IMP (or a medical device) unless the study is UCB UP0017 \[NCT02019602\] or a registry study
* Subject has received treatment with any biological therapeutic agent, or other anti-TNF agents with the exception of CZP, within 5 half-lives prior to obtaining the first sample
* Subject has a positive or indeterminate QuantiFERON®-TB GOLD In Tube test at Screening. In case of indeterminate result, a retest is allowed if time permits; 2 results of indeterminate require exclusion of the subject
* Subject with known tuberculosis (TB) infection, at high risk of acquiring TB infection, or latent TB (LTB) infection. If tested within the 6 months prior to screening and test was negative for TB, and there is no change in the patient's clinical status, nor social, family, or travel history, there is no need for an additional TB testing at screening