A systematic literature search, made in consultation with an information specialist, of PubMed and Embase was performed, from the earliest date of inception through to 6th April 2022. A protocol for the systematic review was prepared locally but not submitted or registered online. The following key terms and their synonyms were used: organ transplantation (with all SOT transplants: heart, lung, kidney, liver, pancreas and small bowel separately mentioned), pregnancy, child. A reproducible search strategy is provided in Supplementary Table S1.

All pregnancies with either a mother or father with a SOT (heart, lung, kidney, liver, pancreas, or small bowel) as well as combined SOT in their history were eligible for inclusion. Articles were included if >1-year follow-up data of the offspring was described. In overlapping articles, the most recent article was included. Articles not written in English, conference abstracts, (systematic) reviews, and meta-analysis were excluded.

Initial selection based on title and abstract was performed by two researchers (JRM and MFC) independently. All disagreements were discussed and, if there was doubt, the study was included for full-text screening, performed by the same two researchers. All discrepancies during full-text screening were resolved by consensus by the same two researchers. All citations of eligible articles and relevant review articles were consulted for Supplementary References. Two articles were identified that were not found in the primary search. The PRISMA (preferred reporting items for systematic review and meta-analyses) flowchart (7) was used to document the number of articles included and excluded, including the rationale for exclusion (Figure 1).

Data extraction was carried out by one researcher (JRM). A second researcher (MFC) independently performed a full-text check for accuracy and completeness. All discrepancies were resolved by consensus of the authors. For each included study the following data was extracted and summarized in two tables: first author, country, study type, follow-up period, number of live births, transplanted organ, immunosuppressive regimen, mean/median birth weight, mean/median gestational age, method of assessment, and the longer-term outcomes. All longer-term outcomes were evaluated, with specific attention for growth, immunological, neurocognitive, and behavioral follow-up and kidney function. Data on intra uterine fetal deaths and miscarriages were not included. Authors of primary studies were not contacted to provide missing data. Biased appraisal of the articles was performed by two researchers (JRM and JRP) (Supplementary Tables S2A,S2B). For prospective and retrospective cohort studies we used the Newcastle Ottawa Scale (NOS) for cohort studies (8). For cross-sectional studies and case reports we used the applicable Joanna Briggs Institute (JBI) critical appraisal checklists (9).

The following definitions were used: preterm: <37 weeks of gestation, LBW: <2,500 g, and catch-up growth: rapid growth in children following a period of reduced growth (10).

A total of 1,664 live births were recorded, of which 78% (n = 1,290) were born after KTx, 17% (n = 287) after LiTx, 2.6% (n = 43) after HTx, 1.4% (n = 23) after combined pancreas-kidney transplantation, 1.1% (n = 18) after LuTx, and 0.2% (n = 3) after combined heart-lung transplantation. In pregnancies of which the complete immunosuppressive regimen was known, 78% of the women used corticosteroids, 49% cyclosporine, 41% azathioprine, and 30% tacrolimus. In 51 pregnancies with a live birth mycophenolate mofetil (MMF) was used for at least part of gestation, in five pregnancies rapamycin, and in one pregnancy everolimus. Two studies did not specify if MMF and/or rapamycin was stopped during pregnancy (12, 13). No congenital abnormalities were mentioned in these live-born children. Details on gestational age and birth weight can be found in Supplementary Tables S2A,S2B. In 15 articles (n = 191 children, 12%) “normal development,” “no problems,” or “doing well” was mentioned without conducting specific tests or parameters (14–28).

Specific results on growth were described in 16 articles (11, 29–43), of which 6 are case reports (29, 36–39, 41). Overall these results indicate that growth development in the offspring of SOT patients is normal. Of the 234 children born after KTx, 219 (94%) had weight and length development comparable to the general population (11, 30–33, 37–40, 42, 43). Sgro et al. reported a significantly higher weight for age and a significantly lower length for age at a mean follow-up of 3.1 years (range 3 months-11 years) in the KTx offspring group compared to the control group (31). Schreiber-Zamora et al. reported no significant differences in the prevalence of overweight and underweight when comparing offspring of KTx recipients (KTR) with offspring of LiTx recipients and a control group. In the transplant group 16.4% had obesity and in the control group 6.3% did (p = 0.072). The theoretical incidence of obesity in the general population (5%) was significantly lower than the incidence in the LiTx (17.1%), the KTx offspring (15.4%), and the overall transplant group (16.4%) (p < 0.001, p = 0.02, p < 0.001 respectively). Prenatal exposure to tacrolimus was associated with a 2.8-fold increased risk for developing a higher body mass index at later follow-up (42).

Catch-up growth was reported in three case reports with three children from KTR and one child from a LiTx recipient (36, 38, 39). Willis et al. also reported impressive catch-up growth in 21 children born with a birth weight <10th percentile (33). In five articles the growth of 86 infants born after LiTx was evaluated; even though birth weight was low, subsequent height and weight development was within the normal range (29, 34–36, 42).

Ten studies focused on immunological follow-up of the offspring (18, 29, 38, 39, 44–49), of which four were case reports (29, 38, 39, 46). In none of the included studies were opportunistic or chronic infections reported. Antibody response to vaccination was normal and no side-effects of vaccination were observed (18, 38, 45, 46). Two studies reported a significantly higher number of children hospitalized due to infectious disease in the KTx offspring group compared to a control group (44, 49). Ono et al. reported that 28.6% of the KTx group compared to 7.5% of the unmatched control group was hospitalized (p = 0.046) (44). All hospitalized children were exposed to tacrolimus during pregnancy. Egerup et al. matched a KTx offspring group aged 0–5 years with a control group in a 1:10 ratio. 41.9% of the KTx offspring compared to 24.8% of the control group were hospitalized due to infectious disease (risk ratio 1.67). The average number of antibiotic prescriptions filled between age 1–5 years was significantly higher in the KTx compared to the controls. However, this difference was not observed in the group as a whole (age 0–5 years) and not for group <1 year (Supplementray Table S2A) (49).

Serum levels of IgA, IgM, and IgG within the normal range were reported (29, 38, 47, 48). Moreover, Drozdowska et al. found no differences in IgG and IgM concentrations between 39 children of KTR and 39 age-matched controls (age one day-15 years) (48). At birth low numbers of total lymphocytes and specific lymphocyte subsets were reported in three studies, but in 28 of these 31 children normal lymphocyte counts were found at a maximum follow-up of 2 years (39, 44, 46). Ono et al. reported a significantly lower percentage of transitional B cells (CD19⁺CD10⁺) and a higher expression of CD154 on CD4⁺ T cells in children exposed to tacrolimus compared to children exposed to cyclosporine (p = 0.029 and p = 0.009 respectively) (44). Pilarski et al. reported that in an offspring group (n = 10, range 5 months-9 years) compared to a control group, cyclosporine-exposed children had significantly higher numbers of CD45RA + R0- T cells and azathioprine-exposed children had significantly higher numbers of CD45RA-R0+ T cells, suggesting that cyclosporine exposure delayed T cell development and azathioprine exposure accelerated T cell development (45). Moreover, children exposed to cyclosporine had a lower and to azathioprine a higher expression of CD29 T cells compared to the control group (45).

In summary, normal response to vaccination and no opportunistic infection were reported but, especially at young age, the results show some alterations in numbers of immune cells in the transplant offspring group and two studies indicate an increased risk of hospitalization for infection.

Sixteen articles conducted specific tests on neurobehavioral development or cognition (11, 13, 29–31, 33, 37, 45, 47, 50–56), of which three are case reports (29, 53, 54). The studies show that neurological development is similar to the general population. Five articles described intelligence quotient (IQ) scores (11, 29, 30, 50, 52). No significant differences regarding global intellectual performance were found when comparing the transplant offspring with the general population or matched control groups at infant, toddler, pre-school, and school age (11, 30, 50). However, Morales-Buenrostro et al. reported that visuospatial working memory might be affected in preschool children born after KTx (p = 0.007) (50). No significant differences in IQ scores were found between children only exposed to cyclosporine and children exposed to both cyclosporine and azathioprine (30). Subgroup analyses with mothers taking MMF prior to their awareness of being pregnant did not show statistical differences in full scale IQ (50). Kocisezwska-Najman et al. found no differences in the distribution of IQ between children born to LiTx and KTx recipients, though children of KTR had significantly higher percentages of preterm birth and LBW (risk factors for lower IQ) (57) compared to offspring of LiTx recipients (52). Devresse et al. reported that 8/21 (38%) children had a grade repetition, which is lower than their country’s general population (60%) (13).

In 296 children neurodevelopmental follow-up was performed without comparison to a control group (31, 33, 37, 47, 53–55). In 87% no developmental problems were reported and in 13% developmental delays, such as the need for educational support or neurological abnormalities such as cerebral palsy, slightly delayed psychomotor development, and intellectual disability, were reported.

Eight studies mentioned specific results on kidney function (12, 13, 26, 32, 33, 58–60). No abnormalities in kidney function were reported in 96% (243/252) of the assessed children. Al-Khader et al. reported no signs of glomerular or tubular defects and no hypertension or proteinuria in 41 children born from KTR at a mean follow-up of 52 months (12). In 95% of these pregnancies a calcineurin inhibitor (CNI, 73% cyclosporine, 22% tacrolimus) was used. Giudice et al. also reported no renal abnormalities in 12 children born from KTR at a mean follow-up of 2.6 years (32). In all these pregnancies cyclosporine was used during pregnancy. Willis et al. reported 4/40 (10%) children with urinary tract abnormalities on ultrasound: one ureteropelvic junction obstruction, one unilateral scar, and two unilateral renal dysplasia (two female siblings). These two female siblings also had abnormalities on urine analyses. 50% of the mothers used cyclosporine during pregnancy. The reported 10% is significantly more than the general population (2.9%, p = 0.036) (33). Dębska-Slizien et al. reported one child with symptoms of glomerulonephritis out of 22 children born to KTR (26). Borek-Dziecioł et al assessed kidney function parameters (urea, creatinine, potassium, and sodium concentrations) in 40 infants (newborns and children aged >1 year, age not specified) born to mothers with a KTx and 40 control infants matched to gestational age. They did not find any significant differences between the KTx and the control group, nor did they find any differences between the immunosuppressive regimens use by the mothers (58). Shaheen et al. analyzed basic kidney function parameters in the blood of offspring born to KTR as well (median age 39 months, range 6–72 months) and did not find problems in renal functioning or integrity (59). Devresse et al. analyzed questionnaires of 21 children born after KTx aged 7–25 years. None of the children reported taking any chronic medication and no one reported a history of chronic kidney disease, renal stones, gross hematuria, or pathological urine dipstick at school medicine (13). Czaplinska et al. assessed liver function (AST, ALT) and kidney function (creatinine and urea) in 51 infants born to mothers with a LiTx (newborns and children aged >1 year, age not specified). They did not find significant differences between the LiTx group and the control group matched to gestational age and time period of birth, except for significantly lower ALT levels in the LiTx group (60).

One study with a relatively large sample size (n = 199 live births) reported significantly more cases of acute bronchitis, systemic lupus erythematosus, and hyperactivity disorders in the KTx offspring compared to the matched control group (p = 0.007, p = 0.025, p = 0.038 resp.) (61). The same study reported a significantly higher number of hospitalizations in the transplant offspring group compared to the control group (65.8% vs. 45.6%, p < 0.001), without specifying the reason for admission (61). One study focused on ophthalmological follow-up in children aged 1 week till >6 years (not further specified); no differences in pathological findings between the offspring of LiTx, KTx and the control group were found (62).

Bar et al. reported no significant difference in the rate of severe disability in the long-term; there were 8% (n = 3) in the transplant offspring group (two cases of cerebral palsy due to extreme prematurity and one deaf child, probably due to a cytomegalovirus infection) and 2.4% (n = 1) in the primary renal disease group (63). In one case report and one retrospective cohort study, two cases of hepatoblastoma at young age (2.5 years and 18 months) were reported: one child of a LiTx recipient and one child of a KTR (36, 43). One child born to a mother with a HTx had a serious, probably hereditary, cardiac insufficiency (64).

One article (11), described longer term follow-up of children born to fathers with a history of a SOT (11). Four children born to three fathers with a KTx were described. At follow-up (age 4 months, 10 months, 11 months and 2 years 7 months) no abnormalities were found on physical examination except for one child with sickle cell trait. The height percentiles were 25th, 25th, 55th, and 75th percentile and the weight percentiles were 10th, 45th, 75th, and 95th. On the Bayley Scales Mental Development Index the offspring scored within the range of normal (82, 83, 105, and 120).