A "conversational approach" is the most successful way of encouraging honest disclosure of drinking habits by pregnant women, a new study says.
This contrasts with previous research that had recommended midwives should use formal screening tools, such as structured questionnaires.
The new study, from Stirling and Edinburgh universities, said it was important to build trust.
It said the questions had to be flexible and not simply asked verbatim.
It is estimated more than 40% of women in the UK consume alcohol during pregnancy, despite there being no known safe level in terms of the health of their unborn child.
International guidelines recommend the use of alcohol screening and brief interventions (SBIs) in antenatal care to identify drinking and offer support to women to reduce the risks.
Typically, SBIs involve a short conversation with a midwife, while women who are drinking more heavily can be offered specialist support.
However, few studies have investigated their implementation.
Dr Niamh Fitzgerald, of Stirling's Institute for Social Marketing, led the study.
She said: "Midwives used several strategies to facilitate honest disclosures, including taking a positive tone in conversations and exploring drinking habits prior to pregnancy or prior to when women realised they were pregnant.
"It was felt that these approaches helped build a trusting relationship between pregnant women and midwives and improved disclosure rates."
Dr Fitzgerald said the study noted a decline in disclosure that coincided with the inclusion of additional, separate, questions about parenting capacity.
She said this raised the possibility that other questions, asked at the same time as alcohol screening, may affect disclosure rates.
On several occasions, midwives found reported alcohol use elicited through standard questions was lower than expected given the known levels of alcohol use in their local area.
Alcohol use in pregnancy can cause harm to the developing foetus, including growth restrictions, low birth weight, pre-term birth, and foetal alcohol spectrum disorders.
There is little evidence of harm from very low levels of drinking but increasing risks as greater amounts are drunk more often.
Dr Fitzgerald worked on the research - funded by Islington Primary Care Trust - with Lisa Schölin, of the School of Health in Social Sciences at the University of Edinburgh.