BackgroundPreconception care comprises a set of prevention and management interventions that aim to identify and modify risks to a woman's health or pregnancy outcome by emphasising factors that must be acted on before or early in pregnancy. This study aimed to ascertain the effect of the preconception care programme offered at UN Relief and Works Agency primary health-care centres in Gaza, Relief and Works Agency, on pregnancy outcomes. MethodsA quasi-experimental, mixed-methods study was done between Aug 16, 2018, and April 30, 2019. A stratified sampling process resulted in the selection of five of 22 UN Relief and Works Agency primary health-care clinics in Gaza, from which a sample of women was selected by the convenience method. A purposive sample of 11 key informants were interviewed. 60 beneficiaries and non-beneficiaries of preconception care also participated in focus group discussions. A structured interview questionnaire and records review were used for the quantitative study, and a semi-structured protocol was used for the qualitative study. Quantitative data were analysed with SPSS version 21.0 and an open coding thematic technique was used to analyse the qualitative data. The protocol of this study was approved by the Gaza Field Office and headquarters of the UN Relief and Works Agency and by the Al Quds University and was given ethical permission by the Palestinian Helsinki committee. All participants provided written informed consent. Findings800 women (400 who received preconception care and 400 controls) were included in the analysis. 188 (47%) of recipients first learned about the service through midwives. 176 (44%) of recipients registered for the service because they were planning to get pregnant. Regarding preconception care activities, 288 (72%) of recipients indicated that they received health advice, 396 (99%) were screened for hypertension, diabetes, and dental and breast problems and given folic acid, and more than 328 (82%) of recipients were counselled about its importance. 368 (92%) of recipients of preconception care took folic acid before conception, compared with 60 (15%) of non-recipients. 232 (58%) of recipients of preconception care and 268 (67%) of non-recipients had complications during their latest pregnancy, including genitourinary tract infection and anaemia. The percentage of women who delivered via caesarean section was 100 (25%) of recipients and 72 (18%) of non-recipients. 92 (23%) of recipients of preconception care and 128 (32%) of non-recipients had complications during their last delivery, especially bleeding. 72 (64%) of recipients and 268 (67%) of non-recipients had a full-term pregnancy. The mean birthweight of babies was 3274·5 g among recipients and 3225·4 g among non-recipients (p=0·2). InterpretationOur study showed that providing preconception care promotes positive maternal outcomes, yet further enhancement is needed. Targeting recipients of service, improving staff communication, informing and counselling prospective mothers, and ensuring compliance with technical instructions are areas that require further attention, as is strengthening monitoring and supervision. FundingNone.