Parental warmth, confidence, and emotional engagement with their children did not differ by biological role in two-mom families
Relationships between mothers and children in families formed by shared biological motherhood. (Golombok, 2023)
Golombok, S., Shaw, K., McConnachie, A., Jadva, V., Foley, S., Macklon, N., & Ahuja, K. (2023). Relationships between mothers and children in families formed by shared biological motherhood. Human Reproduction, 38(5), 917–926. https://doi.org/10.1093/humrep/dead047
Geographic Region: United Kingdom
Research Question: Does shared biological motherhood (a process in which one partner provides the egg and the other partner carries the pregnancy using donor sperm) result in stronger mother–child relationships than donor IVF, in which only one mother has any biological connection to the child?
Design: Cross-sectional comparative study using structured interviews. Data were collected over 20 months beginning in December 2019. Due to COVID-19 restrictions, nearly all interviews were conducted online. The primary measurement tool was the Parent Development Interview (PDI), a validated tool that assesses how parents think and feel about their children, themselves as parents, and their relationship with the child. Each parent in a family was interviewed separately. Parents also answered simple questions about which parent the child seemed closer to, whether they experienced jealousy toward their partner regarding the child, and how the baby was fed (breastfeeding only vs. a mix of breast and bottle). Statistical analysis used multilevel modeling to account for the fact that data came from two parents within the same family. The study sample was large enough for statistical analyses to detect medium-to-large differences, not small ones.
Editor’s Note: The PDI is a validated measure of parental representations, not direct observation of parent–child interactions or children’s attachment. High scores across both groups reflect how mothers think and feel about the relationship but is not the same as directly measuring the relationship itself.
Sample: 60 lesbian two-mother families: 30 families formed through shared biological motherhood (also known as reciprocal IVF or co-IVF or ROPA) and 30 families formed through donor IVF in which only one mother has a biological connection to the child (the same partner’s eggs and uterus are used for the pregnancy). Both mothers participated in all 60 families, for a total of 120 individual interviews. All mothers identified as cisgender. Children ranged in age from infancy to 8 years old. Families were recruited through the London Women’s Clinic. Families were matched as closely as possible for children’s age, followed by child gender, maternal age, number of siblings, and presence of financial difficulties. Recruitment ended when 30 families in each group had both mothers participate. The study did not report on racial or ethnic composition, donor type (anonymous vs. identity-release), whether families had disclosed to their children, or children’s awareness of their conception.
Key Findings
Mothers in shared biological motherhood families and mothers in donor IVF families did not differ in how they felt about their children, how they saw their child’s emotional experience, or how well they could reflect on the relationship. Both groups showed high levels of warmth, joy, confidence, and low levels of hostility or disappointment in their parenting role.
When birth mothers and non-birth mothers across both family types were compared, no differences were found on any PDI variable.
Within the shared biological motherhood families, the gestational mother (who carried the pregnancy) did not differ from the genetic mother (who provided the egg) on any measure of parental representations of the relationship, reflective functioning, or child affect.
The majority of children in both family types were reported as equally close to both mothers. In shared biological motherhood families, about 30% of birth mothers and 33% of non-birth mothers reported the child was closer to the birth mother. In donor IVF families, 37% of birth mothers and 43% of non-birth mothers reported the child was closer to the birth mother. These differences were not statistically significant.
Most mothers in both groups reported no jealousy toward their partner regarding the child. Roughly one-third reported a little jealousy, and fewer than 10% reported considerable jealousy. Rates did not differ significantly between family types.
Feeding arrangements were similar across both groups: approximately 40% of birth mothers in both family types breastfed exclusively, while the majority used a combination of breast and bottle feeding.
Editor’s Note: None of the findings reached statistical significance, which indicates that no large or medium differences were found, not as proof that the family types are equivalent on all dimensions of relationship quality.
Limitations: All families were recruited through a single clinic (London Women's Clinic), limiting generalizability. Because the study began when shared biological motherhood was newly available in the UK, only a small number of eligible families existed, limiting recruitment. The wide age range of children (infancy to age 8) made it difficult to control for developmental stage, which can substantially affect how parents experience the relationship. The study measures parental representations of the relationship rather than directly observed parent–child interaction or child-reported experiences. No information is provided about whether children had been told about their conception or the type of donor used (known, anonymous, identity-release). The study’s framing centers on whether shared biological motherhood improves upon donor IVF by offering more “equal” biological connection. This framing implicitly positions biological connection as a goal worth pursuing and may subtly reinforce the idea that non-genetic parenting is a deficit to be compensated for, even while the findings show no differences.
Applications: This study found no differences in mothers' feelings toward their children based on whether shared biological motherhood or donor IVF was used, suggesting that couples can make decisions based on practical, medical, and personal factors. This study offers preliminary reassurance that worries about the non-birth or non-genetic mother feeling left out did not, on average, materialize, though individual variation will surfaces.
Funding Source: Economic and Social Research Council (ESRC), grant number ES/S001611/1
Lead Author: Susan Golombok is Professor Emerita of Family Research and former Director of the Centre for Family Research at the University of Cambridge, where she conducted longitudinal research on the psychological wellbeing of children in lesbian-mother families, gay-father families, and families formed by assisted reproductive technologies including IVF, egg donation, sperm donation, and surrogacy.
Regulatory Context
In the United Kingdom, the Human Fertilisation and Embryology Authority (HFEA) is the independent regulator overseeing fertility treatment and research involving human embryos.
Shared biological motherhood (reciprocal IVF / co-IVF) is legal and regulated in the UK. Under the Human Fertilisation and Embryology Act 1990 (as amended in 2008), both female partners in a same-sex couple can be recognized as legal parents of a child born through licensed fertility treatment, provided both consent. The non-birth mother is recognized as the “second legal parent.” Same-sex female couples have had access to licensed fertility treatment in the UK for many years.
In 2005, the UK changed its law regulating gamete donation from anonymous to identifiable donation. As of October 2023, donor-conceived people conceived on or after April 1, 2005 can access identifying information about their donor at age 18. Children conceived before the 2005 law change do not have the same legal right to identifying information, though a voluntary register (the Donor Conceived Register) exists for pre-2005 donors and donor-conceived individuals who wish to connect.
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