<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>5</documentType>
<periodOfReport>2003-09-30</periodOfReport>
<notSubjectToSection16>0</notSubjectToSection16>
    <form3HoldingsReported>0</form3HoldingsReported>

    <form4TransactionsReported>0</form4TransactionsReported>

    <issuer>
        <issuerCik>0000896985</issuerCik>
        <issuerName>MOTHERS WORK INC</issuerName>
        <issuerTradingSymbol>mwrk</issuerTradingSymbol>
</issuer>
<reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001270012</rptOwnerCik>
            <rptOwnerName>TUTTLEMAN STANLEY C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TUTTSON CAPITAL CORP.</rptOwnerStreet1>
            <rptOwnerStreet2>P.O. BOX 2405</rptOwnerStreet2>
            <rptOwnerCity>BALA CYNWYD</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19004</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector>
<isOfficer>0</isOfficer>
<isTenPercentOwner>0</isTenPercentOwner>
<isOther>0</isOther>
<officerTitle></officerTitle>
<otherText></otherText>
</reportingOwnerRelationship>
</reportingOwner>
<nonDerivativeTable></nonDerivativeTable>
<derivativeTable><derivativeTransaction><securityTitle><value>Option (Right to Buy)</value>
</securityTitle>
<conversionOrExercisePrice><value>31.80</value>
</conversionOrExercisePrice>
<transactionDate><value>2003-02-07</value>
</transactionDate>
<transactionCoding><transactionFormType>5</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionTimeliness><value>L</value>
</transactionTimeliness>
<transactionAmounts><transactionShares><value>3000</value>
</transactionShares>
<transactionPricePerShare><value>0</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode><value>A</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<exerciseDate><value>2003-02-07</value>
</exerciseDate>
<expirationDate><value>2013-02-07</value>
</expirationDate>
<underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value>
</underlyingSecurityTitle>
<underlyingSecurityShares><value>3000</value>
</underlyingSecurityShares>
</underlyingSecurity>
<postTransactionAmounts><sharesOwnedFollowingTransaction><value>3000</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>D</value>
</directOrIndirectOwnership>
</ownershipNature>
</derivativeTransaction>
</derivativeTable>
<footnotes></footnotes>
<ownerSignature><signatureName>Stanley C. Tuttleman signed by Dan Matthias under of power of attorney</signatureName>
<signatureDate>2003-11-14</signatureDate>
</ownerSignature>
</ownershipDocument>

